The Official AVS Antenna and Related Hardware Topic! [Text View] - Page 49

Don F.

10-26-09, 08:48 PM

guess I will get a combiner, straighten a coat hanger and go for it... I would think it would not be too difficult to get them, as they are only 4 miles away with a full 15 watts.
I had a pretty good signal on the 4228 until Wed and they completely went away.... I'm thinking they must be having transmitter problems.

My problem, discussed here about two weeks ago, was a loose lug screw at the local ch 8 transmitter. Georgia pbs sent me an email today saying that when they went digital they installed a new ac power panel, and one of the main lug screws was not tight or stripped during the install. This causing intermittent power to the transmitter, thus the in & out signal. In fact they were off the air for better than a week, I don't think they knew it, as my little town is in the sticks, and there is no remote monitor at their site. I'm guessing the problem was found last Thrusday has the signal has been good since then.

So the old 4228 is working just fine now...

Tower Guy

10-26-09, 09:16 PM

300ohm

10-26-09, 09:56 PM

Does anyone have any input into if it makes any difference to use 10AWG, QIC, or flatten QIC (my CM3020 uses flat aluminum)?
For folded dipoles and loops, thicker stuff gives a bit wider bandwidth and better SWR in general.
Besides the sand trick, you could also try plumbing tube benders or heating the bend area with a torch before bending. Or a combination of all.

kevm14

10-27-09, 09:00 AM

Up to 31 channels as the leaves fall. I might top 35 if Boston's ION starts coming in. Still haven't received my 5 foot mast section...

systems2000

10-27-09, 11:35 AM

What channel are you trying to receive?

I'm building three yagis (8 directors/60° corner reflector) for WTAJ (RF32), WLYH (RF23), & WPMT (RF47). I'm also building a "Circular" with reflector (13" seperation) for W08EE-D (WNPB - RF8) and WWPX (RF12).

systems2000

10-27-09, 11:55 AM

For folded dipoles and loops, thicker stuff gives a bit wider bandwidth and better SWR in general.

I'm not looking for a very large bandwidth (ie. WTAJ RF32 - WLYH RF23 (maybe W38AN RF33, when it comes on-line) - WPMT RF47 (maybe WGCB RF30 and WGAL RF31 (if it gets approved and built))).

Besides the sand trick, you could also try plumbing tube benders or heating the bend area with a torch before bending. Or a combination of all.

I was trying to use the benders that came with Tube Flaring Kit, but the bend radius is too tight. I could try the sand, but it's a lot easier when the metal is flat. ;):D

systems2000

10-27-09, 12:50 PM

Attached is what I have to deal with.

The WLYH path is the presumed reason for receiving the signal from almost directly North.

V3 is a corrected topo. I checked the FCC database to get a more accurate idea of directions. I noticed that the direction for WPMT & WGCB could also be reflections off the peaks of the US30 pass. The RED paths are not active yet.

David-the-dtv-ma

10-28-09, 10:51 AM

I'm building three yagis (8 directors/60° corner reflector) for WTAJ (RF32), WLYH (RF23), & WPMT (RF47). I'm also building a "Circular" with reflector (13" seperation) for W08EE-D (WNPB - RF8) and WWPX (RF12).
Are all the channels in the same general direction?

If so I would just use #10 or #8 copper like the bare graound wire you can buy off the spool at Lowes. Since it is soft it is easy to bend. I would make a folded dipole at the 1/2 wave with that wire for each channel you want to receive. Arange on a boom the same way a vhf low band yagi antenna for a deep fringe is built. that would be the longest on the back & the shortest on the front. You would space the dipoles like they are on the 4 bay bow tie , except the boom is horizontal & not vertical like the bow tie is. This would max the signal on the wanted channels. The point is why have band on an antenna for channels you are not needed & when you are wanted just a few channels.

holl_ands

10-28-09, 10:51 AM

While working on constructing a single channel yagi yesterday, I tried using QIC tubing for the folded di-pole. I found that trying to get a 1.5" inside radius didn't work very well.

I began thinking that maybe I could hammer the QIC flat and use that as the folded di-pole material (it comes out to 10mm wide by 1mm thick). Does anyone have any input into if it makes any difference to use 10AWG, QIC, or flatten QIC (my CM3020 uses flat aluminum)?
Yes, you can simply hammer flat the section you intend to bend. Since TV
channels are 6 MHz wide, ultra-precision isn't as important as in Ham Bands....

A formula for determining equivalence between a rectangular section element and
a round section element is found in the description for VK5DJ's Yagi Calculator:
http://vk5dj.mountgambier.org/Yagi/Yagi.html

Here's more:
http://fermi.la.asu.edu/w9cf/articles/conform/index.html
http://vk5dj.mountgambier.org/Yagi/Yagi.html

===================================
I compared performance of QICT to AWG12 in a UHF Circular Loop....Folded Dipole would be similar:
http://imageevent.com/holl_ands/loops
QICT provides much better SWR across the band....
3/8-in Aluminum tubing provides improved SWR....
And HICT (half-inch) would be even better....

systems2000

10-28-09, 07:11 PM

Are all the channels in the same general direction?

Take a look at the V3 Topo file I posted above.

systems2000

10-28-09, 08:00 PM

Yes, you can simply hammer flat the section you intend to bend.

Good idea! :cool: I hadn't thought to do that, but I can see the benefit of having a QICT with flat bends.

I compared performance of QICT to AWG12 in a UHF Circular Loop....Folded Dipole would be similar:
http://imageevent.com/holl_ands/loops
QICT provides much better SWR across the band....
3/8-in Aluminum tubing provides improved SWR....
And HICT (half-inch) would be even better....

This is the loop antenna I'm building for WWPX and W08EE-D. How did you go about producing the 13" spacing?

I was thinking about using grey PVC to make a inverse table with the grid strapped to the top square and the circle attached to stand-offs (legs).

holl_ands

10-28-09, 08:57 PM

Although I built Folded Dipole, Loop & Zig-Zags for Hi-VHF, I have not (yet) built & tested
Reflectorized versions. I also have not built any for UHF Band (CM-4228 works, so no need).

Still recovering from a rib injury....but if I build anything it's probably going to be Hi-VHF and
preferably Circular Polarized.....like a Helix.....

"Table" idea sounds good, but "legs" would need cross-bracing (like a real table)
to prevent collapse....which could be some PVC 3x90-deg connectors.....or a
set of "tees" for the legs plus right-angles for the four straight PVC pieces forming
the "table" (to which the reflector screen is attached). [Do you need a picture???]

Here are some construction ideas that might help:
http://home.comcast.net/~ross_anderson/quadix.htm
http://www.af9y.com/helix.htm

blackngold75

10-29-09, 07:47 AM

Thanks for everyone's help, responding to my post a couple of weeks ago. I decided on a Winegard HD7082P to pull in the Philly channels. Unfortunately, my side yard is sort of a swampy mess right now (not so good for supporting a 24-foot ladder:mad: ) and I was tired of waiting, so I quickly set up the antenna in the attic above my garage last night as a temporary thing because I wanted to try it out.

Observations: my attic is not a big as I thought!

Reception is pretty good - I am pulling in most of the Philly channels with signal strength of 3 out of 5 bars or better (Samsung DTB-H260F). No issues at all with WPVI (VHF 6) or WHYY (VHF 12). I am looking forward to getting my mounting/grounding hardware and putting this outside - when I scan for channels I can see the tuner pausing on a couple of stations but not locking them in, so I am hoping being outside with more elevation will get me there. So far, counting subchannels, I have 24 channels. Not too bad.

Thanks again.

300ohm

10-29-09, 12:10 PM

so I am hoping being outside with more elevation will get me there. So far, counting subchannels, I have 24 channels. Not too bad.
Youll probably get another dozen then.;)

jpasadena

10-29-09, 02:52 PM

systems2000:
How did you go about producing the 13" spacing?

If you are asking about building a VHF-Hi loop with
reflector, this is working for me:

http://www.digitalhome.ca/forum/showthread.php?t=112675

Satcom15

10-31-09, 08:50 AM

Tschmidt

10-31-09, 10:27 AM

My question: Can HDTVs (LCD, plasma, etc.) receive them on the same antenna port as digital reception?
Absolutely, the antenna does not care if signal is NTSC (analog), ATSC (digital) or FM radio for that matter.

TVs have separate NTSC and ATSC tuners. Ours (Sony) displays analog channels without the subcarrier indicator, so Channel 2 is analog and Channel 2.1 is digital. It can be somewhat confusing because Digital channels are virtual, the actual RF channel may be different.

If you have to enter local low power channels manually my guess is that they are too weak to display properly. We have a couple nearby and have never been able to receive them. Try plugging you address into the TVfool site to get an idea how strong the signals are in your area.
http://tvfool.com/

/tom

holl_ands

11-01-09, 10:43 AM

I'm curious and maybe this isn't the right place to ask since it may be TV brand dependent - If so please let me know.

There are still a few analog TV stations broadcasting out there according to a sweep I did with a spectrum analyzer a month or so ago (at least in Colorado Springs). These are low power translaters and community access it appears. My question: Can HDTVs (LCD, plasma, etc.) receive them on the same antenna port as digital reception? In other words if I connect an antenna to the TV, it will use the ATSC tuner for the digital channels. However if I manually tune to an analog channel, are the TV's smart enough to use an NTSC tuner and show the image? Just curious.

Thanks
All ATSC capable DTVs retain the ability to decode NTSC signals (which are still used on Cable).
CECB Coupon Converter Boxes and most OTA STBs are an exception...they only decode ATSC.
Those CECB's with "Analog Pass Thru" can bypass the internal ATSC tuner, passing the NTSC
signals to the attached Analog TV....which requires separate R/C for each type signal.

To tune to a digital channel, a user enters "12.3 or 12-3" whereas analog is just "10".

BTW: The terms "NTSC Tuner" and "ATSC Tuner" can be misleading.
For each Coax input, there is only one "Tuner", which filters, amplifies and
downmixes the RF signal....irrespective of what kind of signal it is.

It is followed by a DECODER CHIP, which is a digital signal processor that
selectively performs NTSC, ATSC or (optional) QAM demodulation.
In many of the new DTVs, the decoder functions have been embedded
into the big TV System-On-A-Chip....plus some external memory chips.

If a DTV has TWO Coax inputs, then it has TWO "Tuners". Sometimes
one of these tuners is incapable of performing the ATSC decode job.

Satcom15

11-01-09, 02:43 PM

holls_and & Tshcmidt - Thanks for the information. I kind of thought that's the way things were, but wanted to confirm. I have a 13 in analog TV and extended basic cable. Time to upgrade to get the full advantage of HDTV I suppose. Also, analog bandwidth recovery (project Cavalry) and DTA boxes from Comcast (my local provider) are probably on the horizon. Regrettably, given all the shennanigans Comcast does with HD compression I'm reluctant to go the digital cable route. If only we had FiOS ... *sigh*. Maybe just go OTA and BluRay :D We'll see.
Cheers

Crimson Apostle

11-01-09, 08:02 PM

2) Use heavy gauge antenna pole or galvanized pipe up to a maximum of 10'.

I am wondering how far, if any, I could go above this conventional advice in my situation. I already have my antenna up in one location, but it does not get quite all I hoped but its maybe 70' from some trees, and moving it back to my other chimney will not only make it higher, but about 30' farther away from the trees. (I'll spare the details of my setup --- heights of trees, angle to treetops from current location etc --- unless they become helpful.) Also, there is a deciduous tree about 10' in front of the current location but it would be an issue farther back (and off to the side some).

I have a 14' chimney I will move it to, and can bolt the entire 14' long with mounting brackets into the chimney (not the round-the chimney straps, unless they were somehow more solid which I doubt). Also, the galvanized pipe comes in 21' lengths, so I could have the top 21' of it in one solid piece.

I am going to try this week to get it up with just a 21' piece, but if that does not work I will go higher. Of course, 3' more gets me to the 10' above the mount that is the conventional limit. But could I go above that some safely given that its solid pipe bracketed for many feet into the chimney? If needed, would going 15' above the last mount be stupid?

(I don't want to hassle with guy wires, but if the max safe without them does not quite get what I need then I will; in my city I can go up to 35' high.)

Thanks in advance for any help here!

300ohm

11-01-09, 10:59 PM

If needed, would going 15' above the last mount be stupid?
What antenna and what size galvanized pipe ? Guy wires arent really that much hassle.

Colm

11-01-09, 11:44 PM

Guy every 10' above the last bracket is the rule of thumb. If you do something else you are playing engineer. If you go with something heavier than typical antenna mast, it might be safe. But like 300ohm said, guy wires aren't that big a hassle. And even if you could get by safely with that last 15', your antenna will be more stable properly guyed.

Crimson Apostle

11-01-09, 11:52 PM

What antenna and what size galvanized pipe ? Guy wires arent really that much hassle.

Here is the antenna setup:
Winegard HD 8200U High Definition Platinum VHF/UHF/FM Antenna (HD8200U) (http://www.solidsignal.com/pview.asp?mc=03&p=HD8200U&d=Winegard-HD-8200U-High-Definition-Platinum-VHFUHFFM-Antenna-%28HD8200U%29&c=TV%20Antennas&sku=615798398491)
Winegard AP 8275 Chromstar 2000 Series VHF/UHF Pre Amplifier (AP8275) (http://www.solidsignal.com/pview.asp?mc=03&p=SAP8275&d=Winegard-AP-8275-Chromstar-2000-Series-VHFUHF-Pre-Amplifier-%28AP8275%29&c=Pre-Amplifiers&sku=615798100162)

For now I used 1" (1.25" OD) galvanized, but I could possibly use thicker... I am checking with the installer (a guy who works with me but very good). He said what size to get, and I have no idea how he attached it to the pipe (or how anyone does). He has a number of successful installs in the area, which is impressive given that we are about 65 miles from the stations.

kevm14

11-02-09, 07:34 AM

If I have about 70 feet of quad shield RG-6, what is the minimum bend radius below which I compromise the signal-carrying capability of the cable? I ask because last night I raised my antenna up another 5 feet. Fortunately I left enough slack inside the garage that I had no issues with length. When I left everything loose, and went inside to check the reception, I was mostly pleased. In fact, Boston ION 68.x went from a dead channel to marginal reception. And Boston CW 56.x seemed pretty good. The Boston ION 68 (RF-32) is kind of a heart breaker because RF-32 has about 1.5dB stronger gain on the 14-foot Winegard that I decided against. Maybe I could add a low noise but also low gain amp, so I don't ruin the majority of my channels which are strong.

However, after taping the cable to the mast and taping the small bundle remaining in the garage, it seemed like my signal took a dump. I untaped the bundle in the garage and that seemed to improve the signal. Tonight I am going to try to increase the bend radius where the cable exits the garage and goes up the mast. I took care not to make the bends ridiculous yet it seems a lot more sensitive than I thought....or it's something else and I am barking up the wrong tree.

Tower Guy

11-02-09, 08:43 AM

If I have about 70 feet of quad shield RG-6, what is the minimum bend radius below which I compromise the signal-carrying capability of the cable?

The minimum bend radius is not an absolute answer. RG-6 with solid copper center conductor is more flexible than RG-6 with copper clad steel center conductor. The insulation also varies in rigidity. For these reasons, I always use solid copper center conductor, even though it is more expensive and harder to find than copperweld.

Unfortunately, once the bend radius has been exceeded you may have to replace the cable to get back to the original specs. This is because the dielectric was deformed and the center conductor is no longer located in the center of the coax.

If the cable is after a preamp it's unlikely that a tight bend caused the loss of a station. The gain of the preamp should overcome any extra VSWR losses.

systems2000

11-02-09, 11:35 AM

Crimson Apostle (http://www.avsforum.com/avs-vb/member.php?u=7489591),

I have a CM3020 (10+ years old) mounted on top of a 12' galv. pipe, which is part of a 55' AGL tower. The tower is bolted to the side of my single story house (at the roof peak) and is free standing to 47' (the pipe takes it to 55').

I live in the open and get 50+mph winds on a regular basis. With 8'+ of galv pipe sticking out of the top of the tower (supported by my rotor) and the CM3020 mounted to the very top, I don't get any problems.

Using galv pipe is a lot stronger than antenna pipe, but unless you are using larger diameter pipe, I would follow the 10' rule, but no more than 15'. It's your setup. If the pipe doesn't have a lot of play and you don't have a wind or ice problem, make a judgement call.

Just a note about joining pipes. Try to make sure you have at least one clamp (preferably two - more is always better) between the joint and the free standing section.

systems2000

11-02-09, 11:43 AM

I noticed something interesting over the weekend. It appears the VHF-Low side of my CM3020 is affecting the reception on my Quad (which is over 8' apart in height).

As I rotated my CM3020 to acquire WPMT and WMAR at the same time, my reception of WWPX went out. I stepped outside to take a look at the antenna orientations and saw the the back-side of the CM3020 was directly above the Pyramid.

Interesting piece of information, considering that just two nights prior, I was sitting in the hot tub looking at the CM3020 and thinking about removing the VHF-Low elements.

kevm14

11-02-09, 12:58 PM

The minimum bend radius is not an absolute answer. RG-6 with solid copper center conductor is more flexible than RG-6 with copper clad steel center conductor. The insulation also varies in rigidity. For these reasons, I always use solid copper center conductor, even though it is more expensive and harder to find than copperweld.

Unfortunately, once the bend radius has been exceeded you may have to replace the cable to get back to the original specs. This is because the dielectric was deformed and the center conductor is no longer located in the center of the coax.

If the cable is after a preamp it's unlikely that a tight bend caused the loss of a station. The gain of the preamp should overcome any extra VSWR losses.

I believe this (http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10216&cs_id=1021603&p_id=3035&seq=1&format=2) is what I bought. Then I cut the ends off, ran it, and re-terminated with PPC EX6XL (or whatever they are) compression F connectors.

I definitely haven't bent it in a way that you could consider it to have gotten kinked. Let's say as little as a 2 or 3" bend radius. Is that a problem? I read that the center conductor does need to be centrally placed inside the dielectric. Speaking of which, does the signal actually propagate in RF through the cable, like between the center conductor and shield? Someone was telling me that it just conducts down the center conductor and there's not really a field involved - and the dieletric and shielding are JUST for shielding, not to help the signal propagation. I'm not sure that's true.

I have no preamp but I am wondering if I should add one to help my marginal channels, without hurting my strong ones (i.e. tuner overload). Maybe enough gain to overcome the signal loss from the cable length, plus a little extra for the weak stations. What are my options for the highest quality (low noise) but modest gain preamps? And how close to the antenna must I place it? How about just inside my garage, about 10-12 feet from the antenna? CPA-19? CM7777?

300ohm

11-02-09, 02:10 PM

Here is the antenna setup:
Thats a big boy. I personally wouldnt feel safe with 15 ft unsupported with it with 1 1/4" OD galvanized water pipe.

300ohm

11-02-09, 02:16 PM

Let's say as little as a 2 or 3" bend radius. Is that a problem?
Thats very tight. With quad shield, I would have a 2 or 2 1/2 ft minimum coiled diameter. But the very act of coiling turns the coax into a crude inductor. I would only use the amount of coax needed plus a few feet. A quality preamp on that length of run is definately a good idea.

Colm

11-02-09, 02:40 PM

General rule of thumb for coax bend radius is no less than 10 times the diameter of the cable. For a .25" diameter cable, that would come out to 2.5".

Crimson Apostle

11-02-09, 04:06 PM

Tower Guy

11-02-09, 06:30 PM

Someone was telling me that it just conducts down the center conductor and there's not really a field involved - and the dieletric and shielding are JUST for shielding, not to help the signal propagation. I'm not sure that's true.

You're right, it's not true.

Tower Guy

11-02-09, 06:39 PM

I have no preamp but I am wondering if I should add one to help my marginal channels, without hurting my strong ones (i.e. tuner overload).

That's the conundrum, how to get enough gain without overload.

In most cases the 7777 has too much gain and can overload. In most cases the HDP-269 has enough gain, and even it can overload in a strong signal environment.

The best way to select a preamp is to look closely at the TVfool and FMfool reports, compare the difference between the strongest and weakest TV stations, determine if the angles between the stations can help reduce overload, analyze the antenna selection for it's ability to pick up FM, consider if the antenna is a singe antenna for VHF and UHF or two separate antennas, and make the preamp selection accordingly.

onezero

11-03-09, 09:26 AM

TG, are you a politician?

You don't answer anything with You're right, it's not true..

Which is false (not true) ?:

1. Cable dielectric and shielding is just for shielding

2. Cable dielectric and shielding is to help signal propagation

onezero

11-03-09, 09:36 AM

General rule of thumb for coax bend radius is no less than 10 times the diameter of the cable. For a .25" diameter cable, that would come out to 2.5".

If that is true, I guess the last 15' of the 100' rolls of RG6U Quad Shield I picked up at Home Depot is bad, as they are coiled really tight. However, after using up 2 rolls they seem to be ok as far as I can tell.

oz

Tower Guy

11-03-09, 11:57 AM

TG, are you a politician?

You don't answer anything with .

Which is false (not true) ?:

1. Cable dielectric and shielding is just for shielding

2. Cable dielectric and shielding is to help signal propagation

It really doesn't matter. (Spoken like a true politician.)

onezero

11-03-09, 12:46 PM

It really doesn't matter. (Spoken like a true politician.)

I guess that's why you are a "Special" member as you don't really matter.:)

300ohm

11-03-09, 03:32 PM

If that is true, I guess the last 15' of the 100' rolls of RG6U Quad Shield I picked up at Home Depot is bad, as they are coiled really tight.
You have a point about that, some of the stuff at Lowes or Home Depot could be bad (bad meaning it still works, but the impedance is off) from the get go. The roll diameter used by the cable companies is much larger and doesnt get as tight at the end of their roll as the beginning of the roll at Lowes or Home Depot.

onezero

11-04-09, 08:38 AM

You have a point about that, some of the stuff at Lowes or Home Depot could be bad (bad meaning it still works, but the impedance is off) from the get go. The roll diameter used by the cable companies is much larger and doesnt get as tight at the end of their roll as the beginning of the roll at Lowes or Home Depot.

So how can you determine if it's impedance is off? And if it is off, what kind of a performance hit would it cause? I really don't want to re-do all my cabling as I just replaced all my 20+ year old rg6 with the Home Depot stuff. It was a great improvement BTW.

oz

kevm14

11-04-09, 12:34 PM

Thats very tight. With quad shield, I would have a 2 or 2 1/2 ft minimum coiled diameter. But the very act of coiling turns the coax into a crude inductor. I would only use the amount of coax needed plus a few feet. A quality preamp on that length of run is definately a good idea.

Can anyone help me pick a quality preamp that is A) the lowest noise possible and B) not ridiculous on the gain such that it blows out my strong channels? Price wise, anything under $250 I'd probably consider.

Also, would running the coax down 7 feet of mast be a problem? I assumed not since it is quad shield...but I could have sworn my reception was better when everything was hanging out, un-taped.

kevm14

11-04-09, 12:36 PM

General rule of thumb for coax bend radius is no less than 10 times the diameter of the cable. For a .25" diameter cable, that would come out to 2.5".

Not sure on the diameter but it sounds like I was at the minimum. I've since tried to straighten out the bends...

Also, someone was discussing the two different kinds of center conductor. Monoprice says mine is "18AWG Solid .040ˇ± Bare Copper-Clad Steel Conductor." I can't remember if that is the desired one or not, though.

kevm14

11-04-09, 01:14 PM

That's the conundrum, how to get enough gain without overload.

In most cases the 7777 has too much gain and can overload. In most cases the HDP-269 has enough gain, and even it can overload in a strong signal environment.

The best way to select a preamp is to look closely at the TVfool and FMfool reports, compare the difference between the strongest and weakest TV stations, determine if the angles between the stations can help reduce overload, analyze the antenna selection for it's ability to pick up FM, consider if the antenna is a singe antenna for VHF and UHF or two separate antennas, and make the preamp selection accordingly.

One of the preamps I looked at had a built-in FM trap. I assume that would at least solve the FM problem. My antenna is a Winegard 7697 which I think is a 7-69 unit. I guess FM shouldn't be much of a concern for me.

Is the Antennas Direct CPA-19 (http://www.erwincomputers.com/cpa19.html) any good?

300ohm

11-04-09, 10:29 PM

So how can you determine if it's impedance is off?
With pricey equipment. But the antenna/balun and TV input impedance may not be perfect either and impedance varies with frequency, so in many cases it could work in your favor if the coax impedance is off.

300ohm

11-04-09, 10:33 PM

Monoprice says mine is "18AWG Solid .040ˇ± Bare Copper-Clad Steel Conductor." I can't remember if that is the desired one or not, though.
The most desirable one is the solid copper conductor. But I wouldnt worry about it. You may want to replace it in 5 - 10 years anyway.

Larry Kenney

11-05-09, 03:09 PM

That's the conundrum, how to get enough gain without overload.

In most cases the 7777 has too much gain and can overload. In most cases the HDP-269 has enough gain, and even it can overload in a strong signal environment.

Living just 3/4 of a mile from Sutro Tower which has one VHF and 10 UHF transmitters, I haven't found any preamp that will work. Even the HDP-269 is overloaded.

What I need is about four or five dB of gain. Several of the Sacramento-Stockton stations are received at the 13 to 14 dB SNR level much of the time, so if I could add just four or five dB it would solve my problems with them. I haven't found a preamp that will turn down to that low of a level.

If anyone finds a preamp that will work in a high RF environment, please let us know!

Larry
SF

300ohm

11-05-09, 03:32 PM

I haven't found a preamp that will turn down to that low of a level.
Have you tried the Kitz Tech one ? It has a gain adjustment on it and is low noise.

hayj

11-05-09, 04:24 PM

Can anyone help me pick a quality preamp that is A) the lowest noise possible and B) not ridiculous on the gain such that it blows out my strong channels? Price wise, anything under $250 I'd probably consider.

Also, would running the coax down 7 feet of mast be a problem? I assumed not since it is quad shield...but I could have sworn my reception was better when everything was hanging out, un-taped.

I'm using the HDP-269 (http://www.solidsignal.com/pview.asp?mc=03&p=ANWHDP269&d=Winegard-HDP-269-SquareShooter-PreAmplifier-for-SquareShooter-SS1000-%28HDP269%29&c=Pre-Amplifiers&sku=615798396145) on a 91XG pointed at 169 degrees at a station 50 miles away. However, I'm 15 miles from all the majors station at 308 degrees. I have no problems with overload from the backside. I know the signal is significantly less on the back, but I'm sure there's still plenty there. Here's my tvfool if it helps:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8adf5abaf21f2a

I've considered hooking the preamp to my 4228 pointed directly at the closer stations just to see if it overloads.

rabbit73

11-05-09, 07:00 PM

Living just 3/4 of a mile from Sutro Tower which has one VHF and 10 UHF transmitters, I haven't found any preamp that will work. Even the HDP-269 is overloaded.

What I need is about four or five dB of gain. Several of the Sacramento-Stockton stations are received at the 13 to 14 dB SNR level much of the time, so if I could add just four or five dB it would solve my problems with them. I haven't found a preamp that will turn down to that low of a level.

If anyone finds a preamp that will work in a high RF environment, please let us know!

Larry
SF

This is the tvfool report that I came up with for your location:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8adff1ff2d5b01

Which Sacramento-Stockton stations do you need?:

KCRA NBC 3.1 virtual on real RF CH 35
KVIE PBS 6.1 on 9
KXTV ABC on 10
KOVR CBS 13.1 on 25
KTFK 64.1 on 26
KMMW 47.1 on 28
KSPX 29.1 on 48
KMAX CW 31.1 on 21
KTXL FOX 40.1 on 40
KQCA 58.1 on 46

The NTIA spec for CECB tuner overload is -5.0 dBm, and that's for just one signal and doesn't even consider the gain added by your antenna. So, it looks like you are already at the overload point. I think it's going to be more involved than just finding the right preamp. What will help you is that your strongest local stations and the Sacramento-Stockton stations are in opposite directions so that good F to B ratio antennas will make it possible.

ProjectSHO89

11-05-09, 07:09 PM

Digital Rules

11-05-09, 09:28 PM

If anyone finds a preamp that will work in a high RF environment, please let us know.IMO, there is no amp that would be useful with so much strong RF present. I would imagine at your distance, you have some readings pretty close to 0 dbm already. (OUCH!!) The very forgiving HDP-269 does in fact overload at my location 4 miles outside DC, but is a stellar performer once you get about 10 miles out.

I would concentrate on attenuating as much out of band (especially FM) signals being picked up incidently by the antenna. By giving the tuner some additional breathing room you will have a better chance of improving the reliabilty of the weaker, more distant stations you desire.

kevm14

11-05-09, 09:46 PM

The closest stations I actually point at are 19 miles away, and there are trees, so maybe I will be ok with one of the common low noise preamps.

kevm14

11-05-09, 09:47 PM

I'm using the HDP-269 (http://www.solidsignal.com/pview.asp?mc=03&p=ANWHDP269&d=Winegard-HDP-269-SquareShooter-PreAmplifier-for-SquareShooter-SS1000-%28HDP269%29&c=Pre-Amplifiers&sku=615798396145) on a 91XG pointed at 169 degrees at a station 50 miles away. However, I'm 15 miles from all the majors station at 308 degrees. I have no problems with overload from the backside. I know the signal is significantly less on the back, but I'm sure there's still plenty there. Here's my tvfool if it helps:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8adf5abaf21f2a

I've considered hooking the preamp to my 4228 pointed directly at the closer stations just to see if it overloads.

My antenna has a front to back ratio of 11 to 20dB depending on the frequency. That is a HUGE amount of gain loss.

Digital Rules

11-05-09, 10:09 PM

The closest stations I actually point at are 19 miles away, and there are trees, so maybe I will be ok with one of the common low noise preamps.The HDP-269 would work fine for your situation. If you find it works well on 1 set, but you need more gain for additional splits, you can add a CM distribution amp without risk of overload. I have used this combination just 9 miles outside DC with a 91-XG, and all 4 tuners get reliable reception of all the Baltimore/Washington UHF stations. There is even a 160kw UHF station only 2 miles away(off-axis) that doesn't overload the system.

hayj

11-05-09, 10:19 PM

My antenna has a front to back ratio of 11 to 20dB depending on the frequency. That is a HUGE amount of gain loss.

The 91XG has a quoted front to back ratio of 28 dBi so its huge too but I'm fairly certain I still see signals creeping in from various directions. My guess would be that the quoted values are far from what is realized in real situations. Others here probably would know more than me though. I do know that I was still urged to get the HDP-269 instead of a higher gain preamp by quite a few here even with this antenna. Still, being 19 miles away, my guess is it will work but again, others here have more experience. I saw a drop in my noise levels as well with the HDP-269 once my tuner's amp was mostly out of the picture.

I have one station that comes in marginally due to it's angle. If the 269 doesn't saturate on my 4228 I may pick up a second one. I think if I just reduce the noise from the 4228 feed, that alone will be enough to get it in all the time. If I check this out anytime soon I'll post back the results.

David-the-dtv-ma

11-05-09, 11:34 PM

Larry Kenney

11-06-09, 06:26 PM

Have you tried the Kitz Tech one ? It has a gain adjustment on it and is low noise.

Yes, I tried the Kitz Tech and as I DEcreased gain on it my weak signals got stronger, but I couldn't turn it down enough. :) Signals were best without it. I returned it and got my money back.

Which Sacramento-Stockton stations do you need?:

KCRA NBC 3.1 virtual on real RF CH 35
KVIE PBS 6.1 on 9
KXTV ABC on 10
KOVR CBS 13.1 on 25
KTFK 26.2 64.1 on 26
KMMW 47.1 on 28
KSPX 29.1 on 48
KMAX CW 31.1 on 21
KTXL FOX 40.1 on 40
KQCA 58.1 on 46

KCRA, KMAX and KQCA, which transmit from the same combined antenna, come in about 95-100% of the time, as does KXTV. KVIE and KOVR hang right at the cliff edge - sometimes viewable, sometimes not, and the rest are always below the cliff edge. It would be nice to get about 4 to 5 dB more gain, making the first four stations 100% reliable and bringing KVIE and KOVR above the cliff edge.

I have not tried putting an attenuator in front of the preamp, as suggested by ProjectSHO89. That's something to experiment with!

I do have something like a distribution amp, as suggested by David-the-dtv-man. It's the RCA DT140M Mini Drop Amplifier, and that keeps the four distributed signals at about the same level as connecting the antenna direct to each receiver. KMAX, for example, is 19 to 22 dB with the antenna connected direct to the TV. Connecting the distribution amp and then using one of the outputs gives me the same 19 to 22 dB. I don't gain anything, but I don't lose anything with it either, and I don't overload the receivers.

Is their a distribution amp that will work like the Mini Drop Amp but provide a little more gain of the original signal?

Digital Rules, yes, my strong signals are close to 0 DB. The ones from Sutro are between -3 and -9 dB, so I'm working with lots of signal in one direction and trying to get stations with -95 in the other direction.

I'm open to all ideas! Thanks to all for the suggestions so far.

Larry
SF

Larry Kenney

11-06-09, 06:48 PM

Added comment to Rabbit73... in case this helps any... looking at the TVFool list (and you do have the right location) I get all of the stations in the green and yellow areas, and many in the pink. Channels (RF) 36, 47, 23, 51 are always there and usually there's plenty of headroom above the 15 dB cliff edge. 49 and 50 are like 21, 35 and 46, 95 to 100% reliable.

Larry
SF

kevm14

11-06-09, 07:19 PM

Wow that HDP-269 seems pretty cool. Not as much gain as the big guns, but enough input headroom to avoid clipping originating from pre-amplification. I still worry about overloading the tuner itself but from reading here and a thread here (http://www.highdefforum.com/local-hdtv-info-reception/23092-winegard-hdp-269-revisited.html) I think I'll be ok.

Also, here is the spec sheet (http://winegard.com/kbase/upload/WC-809%20_HDP-269.pdf) and installation instructions (http://winegard.com/kbase/upload/2451964.pdf) if anyone is interested. Very moderately priced, too.

One interesting note in the instructions: it wants you to place the power injector at the TV tuner, up to 150 feet from the preamp.

Specifically,

To maximize the operating life of the amplifier, install the power injector close to the TV receiver (if only one will be used with the
antenna) or the first signal splitter. A maximum preamp-to-power injector length of 150 feet RG-6 or 150 feet RG-59 is acceptable.

Works for me as I have maybe 70 feet and placing it in my living room is more convenient than running some romex and putting an outlet in my garage.

Does anyone think there is a better unit than this for my needs? If not, I'll go for it.

hayj

11-06-09, 08:10 PM

I still worry about overloading the tuner itself

Not sure what tuner your using but if it's anything like the hdhomerun, you should be fine. My guess would be that the preamp saturates before the tuner. The hdhomerun has a fairly large dynamic range handling 40dB above 100% signal level.

kevm14

11-06-09, 09:54 PM

Using a PCIe Avermedia Duet dual tuner (internally). Good luck finding specs.

300ohm

11-06-09, 10:11 PM

One interesting note in the instructions: it wants you to place the power injector at the TV tuner, up to 150 feet from the preamp.
Not that interesting as most preamps hook up the same way, heh.

hayj

11-06-09, 10:17 PM

Using a PCIe Avermedia Duet dual tuner (internally). Good luck finding specs.

I know what you mean. I had to email Silicon Dust tech support to get a translation of percentages for signal quality. The values for signal strength were in their forum from another user asking for them. You might try emailing them if your really concerned.

hayj

11-06-09, 10:22 PM

Anyone know what the deal is with maximizing the life of the HDP-269 by installing the power injector close to the TV? Are they suggesting having a significant distance of coax in between the preamp and power supply? Mine is only a few feet away.

kevm14

11-06-09, 10:27 PM

Not that interesting as most preamps hook up the same way, heh.

I looked at another preamp and they showed you hooking the power supply up within fairly close proximity of the preamp. And that's what I'd expect. Not sure why they'd rather you install the power injector inside your house, just to run the power all the way back up the cable. That seems less desirable for a number of reasons....but hey if it works, that's easier for me to install.

EDIT: Ordered it. I already raised the antenna the most I feel comfortable with. Whatever I get with this preamp is all I am going to get at this address, I think.

Digital Rules

11-06-09, 11:05 PM

systems2000

11-06-09, 11:17 PM

I already raised the antenna the most I feel comfortable with.
Did raising the antenna help any? Remember, you need to find the wave peak along with the height.

With an outdoor antenna, you're going to want a coax ground block (connected to the house electrical ground) between the power inserter and the antenna.

Digital Rules

11-06-09, 11:29 PM

Digital Rules, yes, my strong signals are close to 0 DB. The ones from Sutro are between -3 and -9 dB, so I'm working with lots of signal in one direction and trying to get stations with -95 in the other direction.Wow, -95 in a metropolitan environment will be tough with a single antenna set-up. I just don't see amplification helping you other than distribution for multiple splits. The slightest bit of boost will most likely drown out any chance of getting those weaker stations. The antenna itself will need to do all the work.

The best I can do reliably is around -90 with a 91-XG. http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8ecd2d529b2d8f The 91-XG nulls out the off axis signals well, except for the ones @ 180 degrees. It reliably picks up stations up to 30 miles from the back of the antenna.

Larry Kenney

11-07-09, 02:08 AM

Wow, -95 in a metropolitan environment will be tough with a single antenna set-up. I just don't see amplification helping you other than distribution for multiple splits. The slightest bit of boost will most likely drown out any chance of getting those weaker stations. The antenna itself will need to do all the work.

I guess I'm doing pretty good under the circumstances. The KMAX RF 21, KCRA RF 35, KQCA RF 46 tower is 65 miles away over a 1000' hill that's about 15 miles away, and using a CM4228 I'm getting signals in the 19 to 24 dB SNR range on my Sony receiver. TVFool shows KMAX at -90.2, KCRA at -94.0 and KQCA at -98.3 dBm.

I think my big benefit is the direction of the signals. The power from Sutro Tower is coming from 267 degrees, while the Sacramento stations are at 56 degrees.

Larry
SF

300ohm

11-07-09, 12:03 PM

Not sure why they'd rather you install the power injector inside your house, just to run the power all the way back up the cable. That seems less desirable for a number of reasons....but hey if it works, that's easier for me to install.
The main reason they do that is so they dont have to weatherproof the power supply and making for an easier and safer installation. The downside is a voltage drop on long runs.

Which preamp required a power outlet nearby ?

keeper

11-07-09, 12:39 PM

Digital Rules

11-07-09, 01:02 PM

Does anyone know the capability of the XG91 at getting upper VHF. I am getting two channels out of Baltimore 11,13 at round 62% with a few dropouts. I wonder if I get a VHF antenna how much those signals will improve.Whatever VHF reception you are getting now is purely incidental, as the 91-XG is designed for UHF. Since it does pick those stations up fairly well, a small VHF-HI antenna should improve things quite a bit for you. (You may even get the powerhouse ABC affiliate out of DC depending on you location) I would recommend the inexpensive Antennacraft Y5-7-13 in your situation. http://www.google.com/search?sourceid=navclient&aq=3&oq=antennacraft&ie=UTF-8&rlz=1T4DKUS_enUS306US306&q=antennacraft+y5-7-13 . Keep the antennas at least 2.5 feet from each other if possible. Combine the 2 antennas with a UVSJ into a single downlead. http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4DKUS_enUS306US306&q=uvsj

keeper

11-07-09, 02:11 PM

Whatever VHF reception you are getting now is purely incidental, as the 91-XG is designed for UHF. Since it does pick those stations up fairly well, a small VHF-HI antenna should improve things quite a bit for you. (You may even get the powerhouse ABC affiliate out of DC depending on you location) I would recommend the inexpensive Antennacraft Y5-7-13 in your situation. http://www.google.com/search?sourceid=navclient&aq=3&oq=antennacraft&ie=UTF-8&rlz=1T4DKUS_enUS306US306&q=antennacraft+y5-7-13 . Keep the antennas at least 2.5 feet from each other if possible. Combine the 2 antennas with a UVSJ into a single downlead. http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4DKUS_enUS306US306&q=uvsj

Thanks a lot- that was what I was thinking.

300ohm

11-07-09, 02:55 PM

Does anyone know the capability of the XG91 at getting upper VHF.
Channel 11, 4.45 dBi Raw Gain with a SWR of 158, so a massive negative Net Gain.
Channel 13, 5.1 dBi Raw Gain with a SWR of 159, so a massive negative Net Gain.

keeper

11-07-09, 05:09 PM

Channel 11, 4.45 dBi Raw Gain with a SWR of 158, so a massive negative Net Gain.
Channel 13, 5.1 dBi Raw Gain with a SWR of 159, so a massive negative Net Gain.

Thanks- so the XG91 is poor at receiving those channels?

ThoraX695

11-07-09, 07:42 PM

I'm not in as bad of a situation as Larry Kenney. However, I'm still 6.4 miles away from the closest transmission tower here in Cincinnati and my strongest station is -19.8 dBm. I'm at about 600 ft. and like to receive stations from Dayton, 40 miles north and right behind an 800 ft. hill. I can sporadically pick up WHIO, WPTD, and WDTN (down to a -10.1 noise margin) with my Clearstream C4 with no tropo and with most of the leaves off the trees. (My C4 seems to have eliminated a lot of multipath that's in my area as well. I'm very pleased with its performance during heavy rain and high winds dealing with my core stations.) I'm assuming that the only hope to improve potential reception to the Dayton stations is to upgrade my antenna to an XG91.

I'm not thinking about upgrading soon though. I have two high-VHF stations to deal with (although WCPO has petitioned to move to UHF). Plus, I'm hoping that AntennasDirect would release a newer version of the XG91 that's cut for UHF 14-51 instead of the current 14-69.

Here's my TV Fool plot (http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc27ec0683ac18). I'm open to suggestions!

300ohm

11-07-09, 09:02 PM

Thanks- so the XG91 is poor at receiving those channels?
Well yeah, normally very poor. But as noted on the HDprimer site :
Explanation (non-essential reading)

Why show raw gain when net gain is what is important?

1. If atmospheric noise exceeds receiver noise then the raw gain is what counts. (This is rare for VHF or UHF but does occur in some neighborhoods.)

2. To determine which of two antennas has a narrower beam on a given channel, just compare their gains at that channel. But in this case you use the raw gain, not the net gain. Raw gain is also called directivity.

3. There are cable-matching methods that make the net gain as good as the raw gain for any channel. But while these methods make some channels better, they make other channels worse, and there is seldom an overall improvement. There is presently no hardware available that lets consumers improve the match, except for some indoor antennas.

4. The program that predicts net gain is not very accurate. Net gain is affected by minor details in the way the cable attaches to the antenna. The raw gains are very accurate.

Note that this website is probably alone in using the term “raw gain”. Other references simply call it the gain.

http://www.hdtvprimer.com/ANTENNAS/comparing.html

kevm14

11-08-09, 12:03 PM

Did raising the antenna help any? Remember, you need to find the wave peak along with the height.

With an outdoor antenna, you're going to want a coax ground block (connected to the house electrical ground) between the power inserter and the antenna.

I think it helped but I don't know if I have the patience to try other heights, on top of angles. I was hoping that higher would be better, but with trees that might not necessarily be true I guess.

I should probably add a ground block, though I don't have one at the moment. Do they all pass DC?

Also with the preamp, tell me if my math is correct. 12dB signal gain out of the HDP-269. Let's say 3dB of it is noise (probably somewhat less than that, in reality). That's 9dB net SNR gain when taking into account the noise floor. Subtract another 3dB for cable attenuation (70 feet of RG-6) and that's 6dB net SNR gain to the tuner. Hopefully 6dB (4x) is enough to tune in and stabilize even my 50 mile fringe Boston stations, as well as not over power the tuner on my 19 mile stations. I guess it all depends on what kind of SNR the antenna itself is seeing. If it's marginal then obviously no amount of amplification will help. I remain somewhat optimistic at this point.

hayj

11-08-09, 01:10 PM

I think you'll also see an increase in SNR in the end signal since the tuner will be amplifying less. If your intersted, holl_ands posted this link awhile ago:

http://www.digitalhome.ca/forum/showthread.php?p=879273

On it there's a very useful post that contains a cascaded noise figure calculation spreadsheet. Very helpful to see how various components effect the bottom line.

http://www.digitalhome.ca/forum/showpost.php?p=877838&postcount=605

Digital Rules

11-08-09, 01:51 PM

I should probably add a ground block, though I don't have one at the moment. Do they all pass DC?Yes, you shouldn't really notice much attentuation either.

Hopefully 6dB (4x) is enough to tune in and stabilize even my 50 mile fringe Boston stations, as well as not over power the tuner on my 19 mile stations.I seriously doubt you will see any overload. You can also add a CM distribution amp if you have a few splits in order to maintain adequate gain to each outlet.

I've used this combiantion with an off axis UHF station & 2 FM stations less than 2 miles away. Even the weakest stations 45 miles out are preserved at all 4 outlets.

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc27954ffd5063

ctdish

11-08-09, 02:07 PM

Also with the preamp, tell me if my math is correct. 12dB signal gain out of the HDP-269. Let's say 3dB of it is noise (probably somewhat less than that, in reality). That's 9dB net SNR gain when taking into account the noise floor. Subtract another 3dB for cable attenuation (70 feet of RG-6) and that's 6dB net SNR gain to the tuner. Hopefully 6dB (4x) is enough to tune in and stabilize even my 50 mile fringe Boston stations, as well as not over power the tuner on my 19 mile stations. I guess it all depends on what kind of SNR the antenna itself is seeing. If it's marginal then obviously no amount of amplification will help. I remain somewhat optimistic at this point.

The SNR gain using a preamp depends on several things including than preamp gain but in with most UHF TV setups it will be a bit less than the cable loss plus the difference between preamp noise figure and the receiver's noise figure. These are usually about 3 and 6. So the improvement in SNR will less than be cable loss plus 3 which will be less than 3+3=6 dB for your case.
John

Tschmidt

11-08-09, 05:30 PM

I should probably add a ground block, though I don't have one at the moment. Do they all pass DC?
Yes, a grounding block is basically a F connector mounted on a chunk of aluminum so it can be bolted down.

Also with the preamp, tell me if my math is correct. 12dB signal gain out of the HDP-269. Let's say 3dB of it is noise (probably somewhat less than that, in reality). That's 9dB net SNR gain when taking into account the noise floor. Subtract another 3dB for cable attenuation (70 feet of RG-6) and that's 6dB net SNR gain to the tuner.
My understanding is a little different. The noise figure of the amp - reduces antenna effectiveness. So lets say your antenna is rated as 16dBi, if amp noise figure is 3 dB it is the same as if the antenna had only 13 dBi of gain, connected to a perfect amp. Signal captured by the antenna needs to overcome amp noise figure.

Amplifier gain should be set so signal at receiver is about 10 dB higher then preamp input. Only thing amp does is make up for losses that occur after the antenna, it can't create signal if the antenna does not pick it up. The reason for 10 dB figure that is so signal is larger then noise figure of TV, typically about 6-7 dB. That way TV noise figure can be ignored. Upper bound is determined by overload conditions. Too much is as bad as too little.

Thinking about it in other terms hooking TV directly to the antenna reduces antenna's gain by 6-7 dB, since TVs typically have much worse noise figure then a good preamp. Without preamp, even if TV was very close to the antenna, it would effectively be a 9-10 dBi antenna.

Rule of thumb: preamp gain should exceed cable, connector and splitter losses by at least 10 dB. Upper bound is limited by overload but another 10 dB is probably OK unless you have a lot of nearby stations.

kevm14

11-09-09, 07:39 AM

systems2000

11-09-09, 08:22 AM

Connectors are usually calculated at around 0.2 dB.

Tschmidt

11-09-09, 09:04 AM

Well if this HDP-269 only offers 12dB of gain, then I don't see how I could be above that 10dB figure you mention.
You are pretty close with 3 dB cable loss, a few connectors and no splitters.

from the Winegard blurb:
http://winegard.com/kbase/upload/WC-809%20_HDP-269.pdf

It is designed for urban areas, so extremely low antenna signal level is not going to be a problem. Has enough gain to overcome distribution loss.

If your signals are weak, and there are no extremely strong nearby station may want to look into a preamp with better noise figure and more gain. I'm using a CM 7777 feeding an 8-way splitter that adds 11 dB of loss. You may need to add an attenuator to prevent overload.
Or pick a different Winegard preamp:
http://winegard.com/kbase/upload/chart29.pdf

Keep in mind noise figure only comes into play if the signal is very weak. Even if you you don't hit the magic 10 dB value a preamp will still help, it overcomes cable loss and has a better noise figure then your TV.

hayj

11-09-09, 09:07 AM

Well if this HDP-269 only offers 12dB of gain, then I don't see how I could be above that 10dB figure you mention. My cable loss alone is going to be about 3dB. Not sure about connectors (that was a question I had asked previously). I have no splitters, at least. Do you think the HDP-269 is the wrong preamp for me?

Somebody correct me if I'm wrong, but I think your issue is saturating the preamp, much like mine. This is why many use the HDP-269. You don't have to be at the 10 dB mark, but hitting it keeps your tuner's amp (which is assumed to have a higher noise level than the HDP-269) out of the picture. Getting close is still effective. I have a two way split, a jointenna, and about 20 ft of coax. I saw an increase in signal strength and more importantly, a decrease in noise. If your worried about overloading your preamp, you may not have many options.

One thing about this situation I'm still curious about is the dynamic range. It seems like in a situation like this, you get the gain on the high end from the gain of the preamp, but don't you also gain some useful signal on the low end as well by lowering your noise floor, at least as seen from the tuner? If my tuner has a noise figure of say 7dB and I take the tuner's amp out of the picture by getting around 10dB above all losses (say I have 2 dB of loss in the case of the HDP-269), wouldn't the tuner effectively see another 4dB of signal on the low end, increasing my SNR? Could someone clarify this for me?

RocketGuy3

11-09-09, 12:11 PM

IDRick

11-09-09, 01:24 PM

Rocketguy3, you up for building your own? The mclapp 4-bays have moderate high vhf reception and should be able to acquire all your vhf + uhf stations. Check out the thread on this forum "how to build a UHF antenna". Mclapps plans are here: http://www.frontiernet.net/~mclapp/Antennas/diagrams.html

http://www.frontiernet.net/~mclapp/Antennas/

300ohm

11-09-09, 03:41 PM

but I still can't get ABC (RF channel 8). I guess I need a separate VHF antenna afterall, and then a UVSJ combiner.
At 45.5 NM, you should be able to combine cheap rabbit ears with a UVSJ to get that station.

kevm14

11-09-09, 03:59 PM

If your signals are weak, and there are no extremely strong nearby station may want to look into a preamp with better noise figure and more gain. I'm using a CM 7777 feeding an 8-way splitter that adds 11 dB of loss. You may need to add an attenuator to prevent overload.
Or pick a different Winegard preamp:
http://winegard.com/kbase/upload/chart29.pdf

Keep in mind noise figure only comes into play if the signal is very weak. Even if you you don't hit the magic 10 dB value a preamp will still help, it overcomes cable loss and has a better noise figure then your TV.

Here is my TV Fool report (http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc272da42d1d2d).

As you can see I have a few strong ones, but I'd also like to consistently receive the 22-34NM range (one is already pretty good, WFXT RF 31 but the rest in that range are in and out). My antenna is fairly high gain (WG-7697P) but I have a bit of a tree problem in my neighborhood. The top 4 stations are why I thought I might need the dynamic range of the HDP-269.

BTW, even after raising my antenna 5 feet to about 20 feet, I still haven't decided on ~32° or 45-50° aim. I have been going back and forth between these. They each have different compromises and I was hoping a preamp would bring in everything from one direction. I am at the 45-50° aim currently, as I have done some aggressive limbing in this direction.

IDRick

11-09-09, 04:10 PM

Kevm14,

In your case, it makes sense to aim the antenna at the lower NM towers (29 degrees, compass heading). It will optimize their received signal while taking away only a small amount from the stronger, closer stations at 41 degrees.

HTH,

Rick

kevm14

11-09-09, 05:08 PM

You'd think so but the tree issue may complicate things. 45-50° is a clearer limb/tree path. I also have a problem with CW RF 22, which is off axis. Aimed at 45-50 it seems to work ok. And there is the ION RF 17 behind me that I'd like to keep. We'll see what happens after I install the HDP-269.

systems2000

11-09-09, 06:18 PM

Hello again guys. So I moved in to my new place, and the DB2 I bought a while back seems to work pretty well for the majority of channels I want... but I still can't get ABC (RF channel 8). I guess I need a separate VHF antenna afterall, and then a UVSJ combiner.

One antenna I was recommended before was the AntennaCraft Y5-7-13, but that seems pretty large for my purposes. Is there anything smaller that would do well enough for me? Here's my TVfool data again:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d03fbcdecc582ff

Thanks.

You could try building one of Holl_and's circular antennas. The image links were took today, of the one I'm currently getting ready to install. It's a 23" VHF-High, with a 13" spacing to the reflector, and yes, that's a 750ml wine bottle for size reference.

I found that 14.25" of exposed pipe (don't forget to leave enough for inside the corner connectors) at the base (x4) is what gave me the 23" distance on the stand-off brackets. I cut my stand-off brackets at 15" and used plastic siamese cable clamps (which are used to anchor coax) to hold the QICT at 13". My screen is plain galv. 2"x3" fencing. It is 30" wide by 36" high.

I couldn't find corner connectors that didn't have one of the entrances threaded. I used my Dremel, with a sanding drum, to remove the threads.

hayj

11-10-09, 09:54 AM

Anyone have any suggestions for tightening an 91xg to keep it from turning? It's drifted about 45 degrees in the past couple of weeks and is finally affecting the signal. I'm getting up on the roof sometime this week to turn it back and thought I'd have a plan. From what I recall there's just a couple of wing nuts that I hand tightened. I would rather not take it down and make and major changes if at all possible. Any suggestions?

Digital Rules

11-10-09, 10:03 AM

Anyone have any suggestions for tightening an 91xg to keep it from turning?A pair of pliers is all that is needed to tighten the wing nuts. Don't over-tighten them though. Moderate tightening has kept mine in place for 1 1/2 years, even with all the hot air coming from DC.:D

hayj

11-10-09, 10:19 AM

A pair of pliers is all that is needed to tighten the wing nuts. Don't over-tighten them though. Moderate tightening has kept mine in place for 1 1/2 years, even with all the hot air coming from DC.:D

Thanks. I was worried about over tightening, hence the hand tightening. I'll re-aim, hand tighten and then apply a little extra with the pliers. Glad it was that simple.

jpasadena

11-10-09, 11:34 AM

You could try building one of Holl_and's circular antennas.

[snip]

My screen is plain galv. 2"x3" fencing. It is 30" wide by 36" high.

I am getting good results with a similar build - loop with reflector
for VHF-hi. I found that in my situation, a slightly bigger reflector,
48" x 48", got my weakest channel (13) over the threshold.
I haven't seen anyone model how the reflector size affects gain,
and in my case it may just be getting the reflector into some of
the patchy hot spots I am dealing with. Looks like you could still
play around with reflector size at this point in your build.

AntAltMike

11-10-09, 12:59 PM

I see that someone is listing a used ChannelMaster Parascope 4251 antenna on eBay, presently asking $199 but with no bids yet. The bad news is, he is quoting $158 for shipping, though the listing says you can pick it up in New Hampshire (just outside of Concord).

http://cgi.ebay.com/CHANNEL-MASTER-4251-PARASCOPE-UHF-ANTENNA-THE-BEST-UHF_W0QQitemZ230392889622QQcmdZViewItemQQptZLH_DefaultDomain _0?hash=item35a47c8116

I ran his zip code (Contoocook) through TVfool, and with the digital transition, he is in deep doo-doo. Most of what little analog reception he had was VHF, but nearly all of his old VHF stations have relocated to UHF. He had previously been unable to get the popular Boston UHF stations even in analog, and now that they all are UHF, he is getting zilch for Boston reception

RocketGuy3

11-10-09, 02:52 PM

Thanks for the input guys. I tried a bunny ears before, and it didn't work too well, but maybe I need to find the right one or just give it another try seeing as I only need to position it to pick up one channel this time. I hope that works so I don't have to spend money on another antenna.

I get the feeling that TVFool is at least slightly misleading since if the channels really were all coming in that strong, I wouldn't be having this much trouble with ABC. I also have the occasional dropouts on one or two other channels, but I think an amp might fix that.

I probably could/should build an antenna myself, but I'm just too lazy. =P

ziggy29

11-10-09, 04:06 PM

A pair of pliers is all that is needed to tighten the wing nuts. Don't over-tighten them though. Moderate tightening has kept mine in place for 1 1/2 years, even with all the hot air coming from DC.:D
Worked for me, too. At first I only hand-tightened until my fingers hurt, and it didn't take too many windy days to knock it out of whack. When I adjusted it again, I did the same thing but also added maybe another quarter-turn with pliers. That seemed to work fine, as we've had quite a lot of days with 30-50 MPH gusts and it hasn't moved at all since.

Larry Kenney

11-11-09, 02:21 PM

Splicer010

11-11-09, 02:46 PM

Quick question... what's the advantage of using a joiner/coupler like the Wingard CC 7870 instead of a regular splitter used "backward"?

I have two antennas, a VHF-UHF and a UHF tied together with just a backward splitter. Would I get better results with a 7870?

Larry
SF

Why are you using a VHF/UHF antenna and a seperate UHF antenna? Just curious. I have a VHF antenna, a 2 seperate UHF antennas (3 seperate antennas) and have found that (for me) this to be the best combo. I have VHF and UHF#1 joined using a UVSJ and I joined UHF#2 to UHF#1 via a balun on #2 and coax to another balun on UHF#1. I have 2 UHF 4 bay antennas to get reception from 2 different cities. I have been told it is a bad idea to join the 2 UHF antennas like this, but I get incredibly stable & excellent reception using this method.

Initially I did have reception issues, but I found that I had the 2 UHF antennas too close together. All antennas are on a 10' mast with the VHF at the top, then about 1 foot down (give or take) the first UHF antenna pointed towards one city and then another 1 foot (give or take) the 2nd UHF antenna pointed at the other city.

Here is a picture to give you an idea of what it looks like. The bottom antenna was repositioned after the picture was taken and is now down so the bottom reflector rod rests on top of the PVC vent pipe.
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=151209&d=1251496414

Ratman

11-11-09, 02:57 PM

LOL! You should fix that rain gutter. ;)

kevm14

11-11-09, 03:08 PM

Got my HDP-269 and installed it today (thanks to our veterans of war).

For raw numbers of channels, I tallied 3 different categories.

Total channels and sub-channels received with solid signal: 36
Subtracting currently unused sub-channels: 32
Unused and channels where programming is duplicated (either lower res format or just plain duplicated, across the guide): 26

For example, PBS 2.2 is always a 480 version of 2.1, a 1080i channel.
ABC 6.2 seems to be always a 480 version of 6.1, a 720P channel.
ION 69.1 is a 480 version of ION 68.1.
ION 68.2, 3 and 4 are duplicates of 69.2, 3 and 4, but 69 should be more reliable so I don't need the 68.x's in my guide.

I didn't include channels that share the same network (RI and Boston ABC, RI and Boston CBS, RI and Boston Fox, RI and Boston NBC, RI and Boston CW, etc) because while they MAY share the same prime time programming not everything is the same, so I don't consider them duplicates. The ones above, as far as I can tell, are.

I've got my antenna at about 42°, pointed just to the right of a white pine tree trunk, as that seemed to be the best compromise. Everything is mostly great with just a few fairly infrequent breakups on a few of my tougher Boston channels. I'm a little concerned how this will hold out through next spring as foliage once again thickens but for now things seem nice. At least today. I'll update over the next week or so, because I've seen how inconsistent reception can be on marginal channels, with my tree coverage.

Splicer010

11-11-09, 03:09 PM

;) Yeah, its getting replaced here shortly.

Larry Kenney

11-11-09, 03:36 PM

Why are you using a VHF/UHF antenna and a seperate UHF antenna? Just curious.
I have a channel 12 plus UHF channels 27, 28, 40 and 41 in one direction where I use the combination antenna, and channel 7 plus several UHFs in another direction where I use just the UHF antenna. Channel 7 is strong enough to give me a 90 to 92% signal using just the UHF.

I have a VHF antenna, a 2 seperate UHF antennas (3 seperate antennas) and have found that (for me) this to be the best combo. I have VHF and UHF#1 joined using a UVSJ and I joined UHF#2 to UHF#1 via a balun on #2 and coax to another balun on UHF#1. I have 2 UHF 4 bay antennas to get reception from 2 different cities.
You lost me with that configuration! Glad it works for you.

I'm still wondering if a 7870 will give better results than just a backward splitter.

Larry
SF

Splicer010

11-11-09, 05:48 PM

You lost me with that configuration! Glad it works for you.

I'm still wondering if a 7870 will give better results than just a backward splitter.

Larry
SF

Larry, I figured I would lose you, thats why I posted the picture link for a vsual aid. ;)

Here is the important part of my description:
I joined UHF#2 to UHF#1 via a balun on #2 and coax to another balun on UHF#1.Point being that a splitter or combiner will cause more signal loss than the use of joining the antenna using a balun and a piece of coax and keeping the 2 antennas seperated by at least 1 foot. It worked for me, and is certainly worth a try for you in my humble opinion, as you won't know if it works unless you try.

However, to answer your specific question, the CC 7870 is nothing more than a splitter used as a combiner, with the exception that the 7870 is a mast mount design. Same insertion loss applies to both. So better results is very unlikely.

rabbit73

11-11-09, 05:54 PM

Re: Winegard CC-7870:
http://winegard.com/kbase/kb_tip_results.php?tip_num=291

ProjectSHO89

11-11-09, 06:39 PM

Re: Winegard CC-7870:
http://winegard.com/kbase/kb_tip_results.php?tip_num=291

...which says it's nothing more than a backwards splitter inside that plastic case with a mast clamp...

ROFL!

Splicer010

11-11-09, 07:00 PM

...which says it's nothing more than a backwards splitter inside that plastic case with a mast clamp...

ROFL!

Which is exactly what I said already.;)

Larry Kenney

11-12-09, 02:06 AM

I won't change a thing. My backward splitter is working and apparently the CC-7870 is the same thing in a fancy box.

Thanks, guys!

Larry
SF

Tower Guy

11-12-09, 11:07 AM

I have two antennas, a VHF-UHF and a UHF tied together with just a backward splitter. Would I get better results with a 7870?

In your case the better option is two feedlines and an A/B switch.

AntAltMike

11-12-09, 11:25 AM

And look for what exactly to indicate improper/proper phasing?

IF they are PCB baluns AND they aren't phased identically, I'd be looking for a different antenna manufacturer.

In practice, it's not difficult to tell whether the phasing is correct. If (in the case of a PCB balun) it's necessary to turn the antenna over to phase it properly for stacking I'd call the manufacturer and demand a properly manufactured antenna.

Winegard's current manufacture PCB baluns are shipped in their own small boxes and can be plugged in either way, so if you are planning on stacking two of them in phase, you have to make sure that you plug both of them in the same way.

kovax

11-12-09, 03:13 PM

Thanks to all for the advice. I finally installed the second DB-8 this weekend and it seems to work well (enough). On a good reception day in the past, I was getting signal strength in the mid-60s (as rated by my DishNetwork DVR) with somewhat frequent dropout and bad days with no signal whatsoever (signal strength below mid-50s seems to be interpreted by the DVR as 0). Now signal strength seems to be in the mid-70s. It still bounces around a lot, but significantly less frequent drop outs. I'm hoping that the improvement is real and not just I've had some good reception days lately. Evening and nighttime reception is very good, hitting signal strength in the 80s and 90s.

I was a little disappointed to read earlier posts that the Wingard CC 7870 I installed is just a reverse splitter. 30% loss from each antenna seems to really limit the value of adding a second antenna. Fortunately it seems like I only needed a little bump in reception. Any other suggestions for more effective combining of signals?

Thanks again, Dan

I'm adding an second 8-bay antenna (AntennasDirect db8) to my antenna mast to make a 16-bay antenna as per the instructions on hdtvprimer.com as suggested to me on this forum.

In the primer for building a 16 bay it says: "There is a chance that you will mix up the polarities such that the two antennas subtract instead of add. After the antenna is fully hooked up, you should rotate the antenna to check for this pattern. If so then you have to reverse the connections on one of the antennas."

My question: The output of the AD DB8 is a 75 Ohm coax connection, not the 2-wire output of some antennas. With this setup, is polarity still an issue? If so, what is the solution? Turn the antenna upside down? Disconnect and turn the antenna's transformer box upside down?

I'll be using the Wingard CC 7870 2-way Antenna Joiner Coupler to join the signals.

Thanks, Dan

Splicer010

11-12-09, 03:23 PM

Tower Guy

11-12-09, 06:07 PM

I was a little disappointed to read earlier posts that the Wingard CC 7870 I installed is just a reverse splitter. 30% loss from each antenna seems to really limit the value of adding a second antenna. Any other suggestions for more effective combining of signals?

The previous post referred to adding two antennas aimed in two directions. I believe that you are trying to add gain to an existing antenna using a second antenna in the same direction.

The CC7870 is the right coupler for you. There will be signal addition, not loss.

ProjectSHO89

11-12-09, 07:41 PM

The previous post referred to adding two antennas aimed in two directions. I believe that you are trying to add gain to an existing antenna using a second antenna in the same direction.

The CC7870 is the right coupler for you. There will be signal addition, not loss.

Yes. If you get the antennas and feedlines arranged so that the signals are in phase, you can acheive a theoretical doubling of the signal instead of a halving. In practice, if you get 2.5 dB improvement, you've done very well.

If the antennas are not phased together, then you suffer the loss.

kovax

11-13-09, 10:36 AM

30%? Where'd you get that number from? Try losing 50%. A 2 way splitter cuts the power in half. What you want to do is install a LOW NOISE pre-amp or a low noise amp. Typically a gain of 15dB and should recover what you are losing.

That was from the manufacturer referenced in an earlier post.

http://winegard.com/kbase/kb_tip_results.php?tip_num=291

This is a splitter being used as a combiner.

kovax

11-13-09, 11:06 AM

Yes. If you get the antennas and feedlines arranged so that the signals are in phase, you can acheive a theoretical doubling of the signal instead of a halving. In practice, if you get 2.5 dB improvement, you've done very well.

If the antennas are not phased together, then you suffer the loss.

Yes, I'm getting an overall improvement of signal. The "loss" I was referring to is of the theoretical potential of each individual antenna without a combiner. So instead of getting twice the signal of a single antenna, I'm getting 70% from EACH individual antenna (because of losses in the combiner), adding to something like 140% of the signal I was getting with only one antenna.

What I was asking was whether there was a way to combine the antennas before the transformer box that connects to the cable wire so that you don't need the 7870 combiner (and the associated signal loss) getting closer to the theoretical doubling of total signal. Or does any method of connecting the two result in a similar magnitude of "combiner loss"?

It's really just a theoretical question. I'm pretty happy with the results that I achieved in combining the antennas as I did.

Splicer010

11-13-09, 11:33 AM

That was from the manufacturer referenced in an earlier post.

http://winegard.com/kbase/kb_tip_results.php?tip_num=291

This is a splitter being used as a combiner.

I understand. But the problem is, the loss thru the splitter is the same even when used as a combiner. That "tech tip" is correct that there is a loss, but wrong on the amount of the loss.

Splicer010

11-13-09, 11:50 AM

It's really just a theoretical question. I'm pretty happy with the results that I achieved in combining the antennas as I did.Ultimately that is all that matters, that it works for you.

In my situation, I have 2 UHF antennas pointed in different directions. To join them, I did like you, used a 2 way of high quality as a combiner. The resulting loss of signal was just too great to overcome, even with the use of a +15dB pre-amp. My solution is one that I have already explained and is looked upon as the wrong way that "will do more harm than good". So as I said, in the end the only thing that matters is how it works for YOU. :)

Even though it is working well for you, you are only getting 50% from each antenna since you are running it thru the splitter/combiner. You can still of course have your 'gain' that will makeup for the loss, but it depends on the actual gain as to how much of the loss is overcome. In your case, what you really have achieved is not so much a gain in signal strength, but rather a greater area of reception since you have effectively 'enlarged' the 'capture' area.

Again, what matters is that it works for you and you are satisfied.

Larry Kenney

11-13-09, 02:38 PM

In your case the better option is two feedlines and an A/B switch.

Not when the feed is for a DVR. You have to get all of the stations all of the time, or you're sure to miss something by having the switch in the wrong position.

I have an A-B-C switch for the rest of my system where I can choose from three different antenna systems. You ought to see the antennas on my roof!
A=CM4228 on rotor, B=another CM4228 with Y-10-7-13 on rotor, C=Antennas Direct C5. The antennas for the DVR are a Radio Shack VHF-UHF combo and an Antennas Direct SR-15 UHF tied together with the backward splitter.

This way I get reliable recordings while at the same time I can play around with the other antennas to pull in the more distant stations on the TV. I do have an A-B switch on the input of the DVR in case I want to record a distant station, but normally the switch is left in the A position with the fixed antennas.

It works for me.

Larry
SF

Colm

11-13-09, 03:12 PM

Even though it is working well for you, you are only getting 50% from each antenna since you are running it thru the splitter/combiner.

Not true. You will get 100% of the signal from each antenna, less the loss inherent in the combiner, about .5dB. or about 12%. If the signals are in phase, they will sum. That is why you can get about 2.5 dB if you properly combine the signals of two identical antennas. If they are totally out of phase they will cancel. And if somewhere in between, the result will be in between.

If you get a given channel only from one of the antennas, you will have about 12% less signal strength after going through the combiner than if the combiner was not there, or about 84%.

Splicer010

11-13-09, 03:35 PM

Colm

11-13-09, 04:13 PM

Splitter with 3.5dB insertion loss:

10.5dB input gives two 7 dB outputs. 3dB reduction in each output is due to splitting signal in two. .5dB is due to losses in the splitter.

Same device used as combiner:

Two 7dB inputs sum to 10dB. .5dB lost in the splitter. Output is 9.5dB. Net gain from using two identical inputs is 2.5dB.

Splicer010

11-13-09, 04:21 PM

LOL! What the hell is this:
Splitter with 3.5dB insertion loss:

10.5dB .5dB ---------------7dB out
from -------------- loss from
source splitter ---------------7dB out

3dB of the insertion loss is due to splitting the signal in two. .5dB is loss inherent to the splitter.

Same device used as combiner

7dB source--------------.5dB
loss from----------9.5 dB out
7dB source--------------splitter

Splicer010

11-13-09, 04:24 PM

Colm

11-13-09, 04:39 PM

Then please explain how some members here combine two identical antennas properly spaced and pointed in the same direction using a passive combiner to get 2.5dB gain.

Or please explain how I can combine a VHF antenna and a UHF antenna with a passive device and not more than halve the signal from either one.

Tower Guy

11-13-09, 05:23 PM

Splicer010

11-13-09, 05:30 PM

Then please explain how some members here combine two identical antennas properly spaced and pointed in the same direction using a passive combiner to get 2.5dB gain.

I'm not saying you can't get a +2.5dB gain using 2 antennas instead of a single antenna. I am saying that using a 2 way splitter as a combiner will net a loss of -3.5dB the same as when used as a splitter. You are saying there is only a loss of -.5dB when a splitter is used as a combiner and it just doesn't work that way.

Splicer010

11-13-09, 05:52 PM

Or please explain how I can combine a VHF antenna and a UHF antenna with a passive device and not more than halve the signal from either one.

Just noticed you added more to your post. And now you have me confused. This whole time our discussion has been about 2 of the same antennas, or at least that was the impression I was under. And now you are talking about joining VHF and UHF antennas that are not the same. So which is it?

To correctly join a VHF & UHF antenna, as has been said in post 1661, a UVSJ is needed. A UVSY is not the same as a splitter and as such has lower loss.

I have 2 antennas that are the same, but aimed in different directions, as well as a VHF antenna and they are joined using baluns and a UVSJ. See my earlier post in this thread for details and photos.

MajesticPete

11-14-09, 11:18 AM

Hi, I'm using a TERRESTRIAL DIGITAL Lacrosse A HDTV Antenna With Amplifier installed on the roof of a 2-floor house.

The setup is coax from antenna (roof) goes to the basement into the amplifier (came with antenna, plugs into the outlet) > into an x8 splitter (LaVa, from ebay, cheap, and covers cable/sat/OTR freq., unamplified) > to TV.

To summarize: antenna > ~60ft rg6 > amp > 1ft rg6 > x8 splitter > ~40ft rg6 > TV.

PROBLEM:
if i use the splitter, i get like 3 channels (of about 15), and all 3 are freezing/pixelerated.
if i remove the splitter (connect from amp rg6 to rg6 that leads up to TV, by using just a regular connector) i get possible channels w/ perferct picture.

Is there any other splitter i should try, or are they all the same?

TIA.
-mp

300ohm

11-14-09, 11:42 AM

Is there any other splitter i should try, or are they all the same?
Do you need an 8X split ? Yeah, I would try a different splitter or use a quality distribution amp.

finlay648

11-14-09, 12:09 PM

dr1394

11-14-09, 11:31 PM

:eek:LOL! Sorry partner. A passive combiner does not raise/add signal level. Quite the opposite really.

LOL right back at you. You're the one that's wrong.

Ron

jjeff

11-15-09, 08:36 AM

Not true. You will get 100% of the signal from each antenna, less the loss inherent in the combiner, about .5dB. or about 12%. If the signals are in phase, they will sum. That is why you can get about 2.5 dB if you properly combine the signals of two identical antennas. If they are totally out of phase they will cancel. And if somewhere in between, the result will be in between.

If you get a given channel only from one of the antennas, you will have about 12% less signal strength after going through the combiner than if the combiner was not there, or about 84%.

Colm is 100% correct. I think why splicer010 isn't seeing this is because according to his post "In my situation, I have 2 UHF antennas pointed in different directions" doing this will result in losses. As Clom said above the signals must be in phase(exact same antennas and pointed in the exact same direction). The only way you can have different antennas pointed in different directions and see appreciable gains is if each antenna is a different band(UHF/VHF, VHF high/VHF low, etc.) or separate channel antennas in conjunction with the correct combiners(not just a regular splitter). In this case you will be seeing only particular frequencies on each antenna, they won't be combining same frequency's for a net gain.
Again if you you have a strong enough signal you may have luck with 2 different antennas pointed in 2 different directions with just a simple backwards splitter(in which case that might be good enough for you) but you'd have even better luck doing it correctly.

superorb

11-15-09, 11:16 AM

Splicer010

11-15-09, 01:26 PM

Hi jjeff. I have 2 UHF antennas that are identical make/model but pointed in different directions. Just so you are clear on what I am using. ;)

Quote:
Originally Posted by Splicer010
LOL! Sorry partner. A passive combiner does not raise/add signal level. Quite the opposite really.
LOL right back at you. You're the one that's wrong.

RonToo funny. Please explain to me and everyone else Ron, just how a passive combiner itself can raise/add signal level then.

arxaw

11-15-09, 01:39 PM

superorb

11-15-09, 01:41 PM

What channels do you wish to receive VHF, UHF or both?
I'm not sure really. I'd like to receive HD OTA channels, but I don't know if they're broadcast in UHF or VHF in my area.

keenan

11-15-09, 01:46 PM

I'm not sure really. I'd like to receive HD OTA channels, but I don't know if they're broadcast in UHF or VHF in my area.
Try the below site, just put your zipcode in the form and it will generate a list of the channels available in your area.

http://www.tvfool.com/index.php?option=com_wrapper&Itemid=29

superorb

11-15-09, 01:56 PM

Try the below site, just put your zipcode in the form and it will generate a list of the channels available in your area.

http://www.tvfool.com/index.php?option=com_wrapper&Itemid=29
Ok, got it. I'm only interested in the major networks like ABC, NBC, FOX, etc. It doesn't look like much else that I'd normally watch anyways. I'm only 13 miles form the transmitter so I'm pretty close. How can I tell if these stations are UHF or VHF now?

http://i168.photobucket.com/albums/u177/superorb/Misc/Radar-Digital.jpg

keenan

11-15-09, 01:58 PM

See the two charts at the bottom? There's one for VHF and another for UHF.

It looks to me like all your major nets, CBS, NBC, PBS, FOX, CW are all UHF and the ABC channel is VHF.

superorb

11-15-09, 02:02 PM

See the two charts at the bottom? There's one for VHF and another for UHF.

It looks to me like all your major nets, CBS, NBC, PBS, FOX, CW are all UHF and the ABC channel is VHF.
So it looks like all UHF with the exception of 1 station on the High VHF scale.

keenan

11-15-09, 02:13 PM

So it looks like all UHF with the exception of 1 station on the High VHF scale.

That's what I see, yes.

superorb

11-15-09, 02:25 PM

That's what I see, yes.
So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.

keenan

11-15-09, 02:30 PM

So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.

At 13 miles with line of sight you're not going need much. I use a 91XG myself but that's because I'm a good 60 miles from the transmitter. Hopefully some folks here more familiar with close range antennas will give you some recommendations.

deltaguy

11-15-09, 03:24 PM

So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.

I don't know that a single aim will be possible for all of your channels, such as PBS. You might want to try a single classic bowtie near a window first. I know it is a UHF antenna, but the flat wire also acts as an antenna. I've reliably received rf 9 (Nm db 54) with a bowtie for over a month now. You've got stronger signal there than I have here. It might work. Good Luck.

cpcat

11-15-09, 03:40 PM

Too funny. Please explain to me and everyone else Ron, just how a passive combiner itself can raise/add signal level then.

?

The -3.5db loss on each leg is if it is used to split the signal or assuming lack of phasing if used as a combiner. 3db is 50 percent loss due to the split (or incorrect phase) and .5 db is through-loss.

However, if you phase properly with two identical antennas pointed in the same direction and equal coax lengths to the combiner you'll see increased performance over a single antenna even using a common splitter. The problem is that common splitters just don't phase very well no matter what. That's the reason stripline combiners work better.

In your situation with the antennas pointed in different directions, the -3.5 db loss should be roughly accurate. Additionally, though, you generate multipath which is the reason it would be technically better to use an A/B switch and two downleads.

rabbit73

11-15-09, 04:13 PM

I have found the Apex DT502 to be very useful when trying to solve OTA antenna problems. It gives not only signal strength but also signal quality. It's a measurement bargain even without the coupon. But, the supply has dried up, so I wanted to try the Centronics ZAT502 HD because it has the the same tuner and dual signal bars. The Centronics is in short supply and I noticed that some Sony TVs have a diagnostics screen mentioned in the pdf manual (http://www.docs.sony.com/release/KDL26L5000.pdf)but no screen shots of it.
I went to a local store to look at the diagnostics screen in the menu of a KDL-26L5000 and then ordered a KDL-22L5000. (The KDL-xxM3000 manual (http://www.docs.sony.com/release/KDL26M3000.pdf) also mentions a diagnostics screen.) The diagnostics screen looks like this:

http://i496.photobucket.com/albums/rr328/rabbit73_photos/IMG_0222_1.jpg

Now that I have all three units I am able to make a comparison using them, a SLM (signal level meter), and a 4-way splitter. My previous tests were done in my car to get away from the street traffic in front of my antenna at home that causes the readings to vary (but the signals stay locked when they are strong) and I was able to drive to strong and weak signal areas. I couldn't work that out because having the 22-inch TV in the car was a big logistical problem. I stayed at home, ran the tests at night with light traffic, and used preamps to vary the signal levels. I also rigged up a mic, amp, and speaker to listen for the traffic to ignore readings when cars were passing by.

The first test used two preamps; a CM7777 near the antenna and a RS 15-1115 inline preamp (one of my better RS purchases) before the attenuator to find out where the signal meters maxed out:
antenna-> 7777-> 50 ft coax-> CM power inserter-> RS amp-> attenuator-> 4-way splitter:

Attn Apex Centronics Sony SLM Equiv
dB Q S Q S S Er SNR dBmV dBm
0 100 87 100 89 79 0 25 +18.5 -30.3
3 100 86 100 89 79 0 25 +15.0 -33.8
6 100 86 100 89 79 0 25 +11.9 -36.9
9 100 86 100 88 79 0 25 +8.8 -40.0
12 100 85 100 88 79 0 25 +5.9 -42.9
15 100 85 100 88 79 0 25 +3.1 -45.7
18 100 83 100 87 79 0 25 0.0 -48.8
21 100 79 100 85 79 0 25 -3.5 -52.3
"Q" is quality, "S" is strength.
Sony IF-AGC figures not listed because in all cases they were the same as strength.

The RS preamp was removed, leaving only the 7777 (my normal setup):
Attn Apex Centronics Sony SLM Equiv
dB Q S Q S S Er SNR dBmV dBm
0 100 84 100 88 79 0 25 +3.0 -45.8
3 100 81 100 87 79 0 25 -0.8 -49.6
6 100 78 100 84 79 0 25 -3.9 -52.7
9 100 73 100 80 78 0 25 -7.0 -55.8
12 100 69 100 76 76 0 25 -10.0 -58.8
15 100 66 100 71 74 0 25 -12.9 -61.7
18 100 62 100 67 71 0 25 -15.7 -64.5
21 100 58 100 63 69 0 25 -18.6 -67.4
24 100 54 100 59 66 0 25 -21.6 -70.4
27 100 49 100 54 62 0 24 -25.4 -74.2
30 100 45 100 50 59 0 23 -28.2 -77.0
33 100 38 100 45 55 0 21 -32.0 -80.8
The 7777 was removed (to simulate weak signals) leaving only the coax between the antenna and the attenuator:
Attn Apex Centronics Sony SLM Equiv
dB Q S Q S S Er SNR dBmV dBm
0 100 55 100 58 66 0 24 -22.0 -70.8
3 100 49 100 53 62 0 24 -25.9 -74.7
6 100 45 100 49 58 0 22 -29.0 -77.8

The RS preamp was inserted between the splitter and the SLM because the meter was near the bottom of scale, and I repeated the test just above. The preamp noise figure does not affect the tuners because it isn't in line with them:
Attn Apex Centronics Sony SLM+amp dBmV corr Equiv
dB Q S Q S S Er SNR dBmV for amp dBm
0 100 54 100 58 66 0 25 -6.1 -22.1 -70.9
3 100 49 100 53 62 0 24 -9.3 -25.3 -74.1
6 100 44 100 49 58 0 23 -12.1 -28.1 -76.9
9 100 38 100 44 55 0 21 -14.9 -30.9 -79.7
12 77 27 65 38 55 0 18 -18.1 -34.1 -82.9
15 26V 0 20V 27 55 0 16 -21.2 -37.2 -86.0
18 dropout dropout 55 3099V 13F -24.3 -40.3 -89.1
A "V" after a figure means that it varies; the Sony errors are updated about once every second. An "F" after the SNR means that the display is frozen at that value. Adding even more attenuation makes the Sony screen go black and say "no signal." At least 15.5 to 16 dB SNR is needed to maintain lock.

When aiming or comparing antennas using the signal strength meter you must keep it below the max value (where your meter doesn't go any higher) by using an attenuator. In my case, that would mean keeping it well below 86 for the Apex, 89 for the Centronics, and 79 for the Sony.

Attachment No. 1 shows a Sony "frozen screen" at 13 dB SNR.
Attachment No. 2 is the RS preamp specs.
Attachment No. 3 is the RS preamp diagram. RS used to print diagrams in the manual, but they don't anymore (http://support.radioshack.com/support_video/doc62/62032.pdf). I think that's a mistake, because showing the diagram encourages experimentation, which means more sales. Looking at the diagram, you can see how the RF signal and the DC power are combined on the coax using capacitors and chokes (inductors). Capacitors pass RF but block DC; chokes pass DC but block RF.

MTVhike

11-15-09, 04:16 PM

Yesterday, I installed two Winegard antennas - YA-1713 high VHF, and a 9095P UHF. Each has a plastic box with a PC board balun, to provide 75 ohm connections. However, the UHF one also has a connector for a VHF antenna, so I guess that is a combiner also. I am using a CM7777 preamp with dual inputs, so I don't use the combiner mounted on the UHF antenna, so I put a 75 ohm cap on that input. How does this configuration relate to the discussions above?

This appears to work well, pulling in WNJN RF 51 in New Jersey, 55 miles away fairly well. I still don't get WCBS RF 22 or WWOR RF 38 (I get all the other NYC stations, as well as some CT ones). Tomorrow, I am getting a 24 ft mast to raise this assembly (currently the VHF one is about 1 ft above my porch roof, and the UHF one is below it - my current 10 foot mast is mounted on my deck). Any suggestions? I'll post a photo of this assembly when I can get one (it's nightime now).

superorb

11-15-09, 04:25 PM

I don't know that a single aim will be possible for all of your channels, such as PBS. You might want to try a single classic bowtie near a window first. I know it is a UHF antenna, but the flat wire also acts as an antenna. I've reliably received rf 9 (Nm db 54) with a bowtie for over a month now. You've got stronger signal there than I have here. It might work. Good Luck.
I'm only interested in the major networks like ABC, NBC, FOX, CBS.

arxaw

11-15-09, 04:30 PM

So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.Before you build one, you might want to try this specific model (Catalog # 15-1874) indoor VHF/UHF antenna (http://www.radioshack.com/product/index.jsp?productId=2103077) which is very inexpensive and has worked quite well for many AVSForum members that are not very far from the towers.. You can use it indoors or (better) in the attic, with a coax extension.

The loop part of the antenna is for all the UHF channels. The dipole "rods" are for the lone VHF (abc) channel in your area. Extend each rod about 13" each and in a "V". Aim the antenna perpendicular to the towers.

If it doesn't work, just return it for a refund and come back here for more suggestions.

deltaguy

11-15-09, 05:26 PM

I'm only interested in the major networks like ABC, NBC, FOX, CBS.

If the top 6 channels on your tvfool chart are all that you need, then you probably won't need multiple aims. I can only say probably though. If multiple aims are required, these are easier to accomplish if the antenna is not in the attic. If multiple aims are not required, then a single trip to the attic should do the trick. The RS budget antenna is both VHF and UHF and probably a good bet. You might also be able to receive those top 6 channels with a pair of rabbit ears alone. Yes, rabbit ears do pick up UHF signal as well.
I'm watching Fox on rf 40 right now with a pair.

dr1394

11-15-09, 07:11 PM

Too funny. Please explain to me and everyone else Ron, just how a passive combiner itself can raise/add signal level then.
It's simple. A splitter is a reciprocal device. The input and outputs ports are interchangeable. As a splitter, if we apply 10 microwatts to the input port, we get (ignoring losses for now) 5 microwatts on each output port. As a combiner, if we apply 5 microwatts to each input port, we get 10 microwatts on the output port.

What is so difficult to believe about that?

http://www.w8ji.com/combiner_and_splitters.htm

Ron

Splicer010

11-15-09, 07:25 PM

It's simple. A splitter is a reciprocal device. The input and outputs ports are interchangeable. As a splitter, if we apply 10 microwatts to the input port, we get (ignoring losses for now) 5 microwatts on each output port. As a combiner, if we apply 5 microwatts to each input port, we get 10 microwatts on the output port.

What is so difficult to believe about that?

http://www.w8ji.com/combiner_and_splitters.htm

Ron

:rolleyes: Incredible. I hope you aren't really a dr and just play one on the internet. I know exactly what a splitter is and what it does. I've only used them professionally for 27+ years. Nobody here that I am aware of, including myself, has ever denied the fact that combining 5+5=10 on the output. The whole point is that a PASSIVE combiner cannot add or raise the signal. The ONLY way to raise the signal is to raise the input level. I'll say it again, it is IMPOSSIBLE for a PASSIVE combiner to raise/add signal level on its own. The key word is PASSIVE. Now if you are talking about an ACTIVE combiner (and you are not) that would be a different story.

dr1394

11-15-09, 08:33 PM

Nobody here that I am aware of, including myself, has ever denied the fact that combining 5+5=10 on the output.
You disagreed with Colm, yet he is saying exactly the same thing. 5 + 5 = 10. I'm not sure what your point really is.

Ron

Splicer010

11-15-09, 09:18 PM

You disagreed with Colm, yet he is saying exactly the same thing. 5 + 5 = 10. I'm not sure what your point really is.

Ron

Ummmm, you really should read the entire conversation before you just jump in and say to me:You're the one that's wrong.
Had you done so you would have seen that this is what I was saying:I'm not saying you can't get a +2.5dB gain using 2 antennas instead of a single antenna. I am saying that using a 2 way splitter as a combiner will net a loss of -3.5dB the same as when used as a splitter. You are saying there is only a loss of -.5dB when a splitter is used as a combiner and it just doesn't work that way.Colm is stating that instead of a -3.5dB loss when used as a splitter, that when used as a combiner the loss is +3dB less and is only -.5dB. I corrected him and you are saying I am wrong, when it is the both of you that is wrong. That has been, and remains still as my point.

And since this has been so blown out of proportion and you guys seem so confused about all this, and post pointless links about combiners, then this will really blow your minds: The -3.5dB loss is PER LEG and not the total loss.

dr1394

11-15-09, 09:26 PM

Are you saying that splitters and combiners are two different things?

Ron

Splicer010

11-15-09, 09:36 PM

Are you saying that splitters and combiners are two different things?

Ron

:rolleyes:Are you just being a troll or what? Because now it is my turn to ask, what is your point? :confused:

Did you bother to do what I told you about reading the whole conversation before jumping into it? Ehhhhh...no. I didn't believe you did. So go back and read the WHOLE conversation from the BEGINNING Ron.:rolleyes:

dr1394

11-15-09, 09:52 PM

:rolleyes:Are you just being a troll or what? Because now it is my turn to ask, what is your point? :confused:

Did you bother to do what I told you about reading the whole conversation before jumping into it? Ehhhhh...no. I didn't believe you did. So go back and read the WHOLE conversation from the BEGINNING Ron.:rolleyes:
I'm not trying to be a troll and I have read the whole conversation. I'm just trying to clearly understand where you're coming from.

On one hand, you agree that a combiner can add two 5 microwatt signals to produce a 10 microwatt signal (ignoring losses). On the other hand, you state that a splitter being used as a combiner will attenuate each leg by 3 dB, therefore applying two 5 microwatt signals will produce 2.5 + 2.5 = 5 microwatts.

So I asked you, "are splitters and combiners two different things?" because that is what you are implying.

Ron

Splicer010

11-15-09, 10:31 PM

A combiner is a splitter.

On one hand, you agree that a combiner can add to two 5 microwatt signals to produce a 10 microwatt signal (ignoring losses). On the other hand, you state that a splitter being used as a combiner will attenuate each leg by 3 dB, therefore applying two 5 microwatt signals will produce 2.5 + 2.5 = 5 microwatts.Ehhhhhhh...no. Ignoring losses then 5 in + 5 in = 10 out. Not ignoring losses then 5 in + 5 in = 3 out. This really isn't complicated as you are trolling, err, trying to make it.

And you ask me why I can't understand.:rolleyes:

dr1394

11-15-09, 11:06 PM

A combiner is a splitter.
Okay, that's a starting point. Then why is the loss entirely different in one direction versus the other? How can a passive network know about direction?

As a splitter, the loss is 3.5 dB per leg. We put in 10 microwatts on the input and we get 4.47 microwatts on each output. The total loss is 10 - 4.47 - 4.47 = 1.06 microwatts or 0.5 dB.

As a combiner, the total loss is the same. We put in 5 microwatts on each input and get 5 + 5 = 10 microwatts minus 0.5 dB or 8.91 microwatts on the output.

Ron

L David Matheny

11-15-09, 11:18 PM

:rolleyes: Incredible. I hope you aren't really a dr and just play one on the internet. I know exactly what a splitter is and what it does. I've only used them professionally for 27+ years. Nobody here that I am aware of, including myself, has ever denied the fact that combining 5+5=10 on the output. The whole point is that a PASSIVE combiner cannot add or raise the signal. The ONLY way to raise the signal is to raise the input level. I'll say it again, it is IMPOSSIBLE for a PASSIVE combiner to raise/add signal level on its own. The key word is PASSIVE. Now if you are talking about an ACTIVE combiner (and you are not) that would be a different story.

I think I'm with dr1394 on this one, FWIW (maybe not much; I'm no expert).

Have you ever heard of a transformer? They're used to step voltage up as well as down, and they're passive. They do have some inherent losses going either way, of course, but that may only be a few percent. They work fine for the power company, among others.

KenL

11-15-09, 11:38 PM

...then this will really blow your minds: The -3.5dB loss is PER LEG and not the total loss.That is simply not true in theory (or in practice) when using a typical hybrid splitter/combiner in the fine art of ganging or stacking phased antennas. :)

Think about it... if you are only getting half of each whole antenna (plus some loss) then the stacked duo would have less gain than the single whole, and there would generally be little benefit to doing it phased beyond some nulls.

You and Colm are really both half correct. In your configuration you are losing up to -3.5 per leg not -.5 per Colm. But when both legs are in phase and equal then it instead approaches +2.5 after the -.5 loss and this is why the hybrid splitter/combiner can be so effective for such application.

Now they sure aren't all created equal and I'd still rather have a stripline to play around with, but with careful attention to phasing the simple 49 cent hybrid T works wonders with both improved gain and desired nulls used with a perfectly balanced gang of two.

Read this section about Superposition analysis (http://www.hdtvprimer.com/ANTENNAS/ganging.html) to get better idea how the circuit behaves in these two different situations.

...The doubling of the output power is equivalent to a 3 dB increase in the signal. If the combiner is 90% efficient then a 2.5 dB gain is seen. Note the dichotomy:

· If the antennas point in different directions, there is a 3.5 dB loss at the combiner.

· If the antennas point in the same direction, there is a 2.5 dB gain at the combiner.

This is a 6 dB swing. 3 dB of this is just the adding of the second antenna, but the other 3 dB is from the combiner becoming a much more effective device.

Obviously in such case the loss is not -3.5dB PER LEG and field experience backs up the good dr's theory here.

If you don't still don't believe it try both configurations (matched same direction, unmatched different directions) for yourself. :)

arxaw

11-16-09, 06:41 AM

http://i32.tinypic.com/20rkxoh.jpg

superorb

11-16-09, 08:15 AM

Can't we all just get along?

SWHouston

11-16-09, 09:39 AM

superorb,

HA ! :D, "Get Along", you GOT to be kidding ! :eek:

Agreed, you can get along with a Modified Range (Ch7-69) Antenna.

Additionally, from what I see on your Chart, and knowing that at times one really likes to "look around", you'd be limiting your Channel selection a lot, by getting a relatively Directional Antenna.

If you want to pick up that WRPX Ion AND your Majors without Rotating, you might think about one of the Omni's.

Just to get you started in that direction, take a look at...
Winegard MS2002 (http://www.solidsignal.com/prod_display.asp?prod=MS2002)

Then, at the bottom of the above Page/Link, there are several other applicable Antennas listed. Check um out !

Have a good Day ! :)
S.W.

superorb

11-16-09, 09:46 AM

SWHouston

11-16-09, 11:26 AM

superorb

11-16-09, 11:34 AM

superorb,

Ok then, this is close, look at the...
Winegard HD7000R (http://www.solidsignal.com/pview.asp?mc=03&p=HD-7000R&d=Winegard-HD7000R-VHFUHFFM-DTV-TV-Antenna-(HD7000R)&c=TV%20Antennas&sku=615798398965)

You can just aim it at your Magnetic 124°, and enjoy !

Have a good Day ! :)
S.W.
Anything that's $25 after shipping? I found this 2-Bay Bowtie Antenna (http://www.summitsource.com/directv-2-bay-uhf-antenna-hdtv-digital-channel-14-69-by-eagle-aspen-dtv2buhf-two-bay-hd-bowtie-tv-outdoor-roof-top-local-signal-bow-tie-aerial-red-zone-part-dtv2buhf-p-6754.html) for $24.xx shipped.

IDRick

11-16-09, 11:46 AM

Superorb,

Follow Arxaw's suggestion. He knows his stuff. His recommendation should work well for you and is priced at half your $25 limit.

Tower Guy

11-16-09, 12:09 PM

2-Bay Bowtie Antenna for $24.xx shipped.

That antenna is not designed to receive VHF. WTVD is on VHF. If you try to go any cheaper than the suggestions, be prepared to have reception issues with WTVD.

The Antennacraft HBU-22 is another cheap antenna that will receive WTVD.

superorb

11-16-09, 02:12 PM

Superorb,

Follow Arxaw's suggestion. He knows his stuff. His recommendation should work well for you and is priced at half your $25 limit.
Alright, I'll give the RS antenna a shot.

SWHouston

11-17-09, 10:38 AM

I'd like to build an antenna for my attic to receive OTA signals. According to AntennaWeb I need a "Yellow" type antenna. Is the basic 4-bay DIY antenna the best for my purposes? The 1st post hasn't been updated in years so I figured I'd post.

Excuse me, but, the...
Radio Shack T#749 (http://www.radioshack.com/product/index.jsp?productId=2103077)
is an Indoor (top of TV) Antenna, no wonder it's cheaper.
Nothing that I recall was ever said about an Indoor Antenna.
I don't know if this little guy has enough punch to get through the shingles, apparently you've changed your mind,
and as Arxaw suggests, use it on top of the TV ?

Have a good Day ! :)
S.W.

superorb

11-17-09, 10:41 AM

Excuse me, but, the...
Radio Shack T#749 (http://www.radioshack.com/product/index.jsp?productId=2103077)
is an Indoor (top of TV) Antenna, no wonder it's cheaper.
Nothing that I recall was ever said about an Indoor Antenna.
I don't know if this little guy has enough punch to get through the shingles !

Have a good Day ! :)
S.W.
Please look at post #1681. (http://www.avsforum.com/avs-vb/showthread.php?p=17539740#post17539740)

arxaw

11-17-09, 04:48 PM

superorb,
thanks.

Using the suggested antenna (http://www.radioshack.com/product/index.jsp?productId=2103077) in the attic may help isolate it from all the RF noise from your TV and other nearby electronics in your home that can muck with VHF reception. In the past, when I lived fairly close to TV towers, using a similar "indoor" antenna in the attic worked very well for nearby VHF & UHF stations. I believe this particular antenna is somewhat better than the one I used, mainly because the UHF loop is larger than most others.

If it doesn't work, it's cheap and it's returnable.

BCF68

11-17-09, 05:04 PM

Anything that's $25 after shipping? I found this 2-Bay Bowtie Antenna (http://www.summitsource.com/directv-2-bay-uhf-antenna-hdtv-digital-channel-14-69-by-eagle-aspen-dtv2buhf-two-bay-hd-bowtie-tv-outdoor-roof-top-local-signal-bow-tie-aerial-red-zone-part-dtv2buhf-p-6754.html) for $24.xx shipped.

And I can tell by the gains they list that it's not optimized for the new UHF channels since it gives the best gain at CH 69. I can make the same antenna actually optimized for 14-51 for about 1/3 of that or less.

arxaw

11-17-09, 05:09 PM

But it's UHF-only.

superorb

11-17-09, 05:13 PM

IDRick

11-17-09, 05:47 PM

And I can tell by the gains they list that it's not optimized for the new UHF channels since it gives the best gain at CH 69. I can make the same antenna actually optimized for 14-51 for about 1/3 of that or less.

What specs do you recommend for a 2-bay? I've built a mclapp 2 bay with 10 inch whiskers, 9.5 inch bay spacing, and 1-3/4 inch phase line spacing. It works very well on UHF, about 3 dB less than a mclapp 4-bay. Unfortunately, high VHF really takes a hit on the two bay, especially if you add a reflector. Have you seen these same issues?

Thanks!

Rick

cpcat

11-17-09, 06:14 PM

IMPOSSIBLE[/B] for a PASSIVE combiner to raise/add signal level on its own. The key word is PASSIVE. Now if you are talking about an ACTIVE combiner (and you are not) that would be a different story.

If you combine two antennas properly then you get more signal than that of one antenna. How close you get to the theoretical doubling of the signal (3db) depends on how well it is done.

I'm not sure of exactly what you are trying to argue at this point.:confused:

BCF68

11-17-09, 06:19 PM

What specs do you recommend for a 2-bay? I've built a mclapp 2 bay with 10 inch whiskers, 9.5 inch bay spacing, and 1-3/4 inch phase line spacing. It works very well on UHF, about 3 dB less than a mclapp 4-bay. Unfortunately, high VHF really takes a hit on the two bay, especially if you add a reflector. Have you seen these same issues?

Thanks!

Rick

Well to be honest based on my own experience I think if you want high VHF you need to go with the 4 bay. I'm not sure there is a way around that short of making a 2 bay specifically for hi-VHF then you're talking about 28 inch whiskers. Of course I have no idea what the phase-line separation for that would be. Might be fun just to try.

I will say that when using a non solid reflector on either a 2 bay or 4 bay I get better signal strength from hi-VHF when the antenna facing backwards from the station. I am not sure why.

IDRick

11-17-09, 06:28 PM

thanks BCF68! I've never tried reception from the back side. I'll give it a try! :)

Best,

Rick

cpcat

11-17-09, 06:34 PM

Again, the take home about using common splitters as combiners in antenna stacking is that they simply don't PHASE very well. That's what stripline combiners are for. Using a common splitter can still work though when doing a dual stack---and provide increased gain as well as narrower beamwidth in the plane of stacking.

To illustrate the difference in the phasing properties b/w common splitters and a stripline, just try using a 4-way common splitter to do a quad. It just doesn't work at all, again not because of signal loss per se, but rather the 4-way just won't phase the signals. Use 3 two-ways though and it will work, although not nearly as good as a stripline will.

Tower Guy

11-18-09, 10:26 AM

I'm not sure there is a way around that short of making a 2 bay specifically for hi-VHF then you're talking about 28 inch whiskers. Of course I have no idea what the phase-line separation for that would be. Might be fun just to try.

Theoretically, the phasing lines should be the same diameter and separation as the UHF version.

superorb

11-18-09, 10:44 AM

arxaw

11-18-09, 11:30 AM

Cheap RS antenna is hooked up and I can tune CBS, NBC, ABC and FOX with a little distortion on each depending on the direction the antenna is pointed. I've got it between the TV nd a speaker, and it's sitting on top of a subwoofer. Signal was worse behind the TV. I think I'll buy a coax coupler and extent the cable into the attic to see if signal improves.
As to be expected. All the electronics in the room give off a lot of noise that affects indoor reception. If the antenna is in an interior room of your house, away from exterior walls, the attic trial should give you better results.

Use as short a length as possible of RG6 coaxial cable and a "barrel splice (http://i25.tinypic.com/2pq5bpe.jpg)" to join it to the antenna. Do not use a splitter.

Make sure the dipole rods are not extended longer than they should be for your VHF channel (~14" each). Point the antenna like this:
http://i48.tinypic.com/23tjxhw.jpg
In your case, the red arrows are NW and SE
The rods should be in a much wider "V" than shown in this picture.

superorb

11-18-09, 12:05 PM

arxaw

11-18-09, 03:33 PM

^^ Aiming it NW/SE doesn't seem to work as well as if I aimed it N/S for some reason. I don't mind getting up and rotating it based on the show I'm watching though. When I get around to buying a taller ladder I'll move it to the attic.Indoors, you may be using reflected signals, requiring aiming the antenna in a direction other than toward the towers. This type of antenna is not as directional as some others. So often times, where you have it sitting may be more important than what direction it's facing.

Until you get a ladder for the attic, you can experiment by moving the antenna around the room or to an adjacent room, using a longer piece of coax. Try different heights - from up near the ceiling to down on the floor. An exterior wall and near a window is usually best. With a little patience, you may find an interference-free hot spot for all your channels, so you won't have to keep mucking with the antenna.

RickCain2320

11-19-09, 12:40 PM

I'm using a trusty old Radio Shack VU-190 in my attic, and due to the preponderance of religious channels and very few secular ones in my area, I would appreciate any tips on getting reception from some of the more remote stations in my area. Pointing the antenna to the close ones is easy since they're clustered in one particular area, but the ones south of me are a bit spread out.

TV Fool Plot attached...

I have a CM4221 laying around unused too. I haven't compared it to the VU-190 yet.

Any help would be appreciated.

300ohm

11-19-09, 02:21 PM

Pointing the antenna to the close ones is easy since they're clustered in one particular area, but the ones south of me are a bit spread out.
You mean those 2 edge, negative NM ones ? You really dont have much (or any) of a chance getting them consistantly with an attic location.

If it wasnt for your channel 7 and 11 stations, the CM4221 would do you fine in a much smaller package than the VU-190. Since those two stations are fairly strong, you may be able to get them with the CM4221 if you electrically attach a couple of 32 - 40 inch rods to the CM4221's reflector. Then you could reclaim a lot of your attic space, heh.

ctdish

11-19-09, 02:26 PM

The signals to the South of you are very weak. If you aim the antenna at them now can you get anything from? This level probably means that with any set up they will not be reliable. You will need a properly aimed outside antenna with a preamp for best results. The preamp requirement along with the very strong signals adds a great deal more difficulty to your problem.
John

RickCain2320

11-19-09, 03:42 PM

You mean those 2 edge, negative NM ones ? You really dont have much (or any) of a chance getting them consistantly with an attic location.

If it wasnt for your channel 7 and 11 stations, the CM4221 would do you fine in a much smaller package than the VU-190. Since those two stations are fairly strong, you may be able to get them with the CM4221 if you electrically attach a couple of 32 - 40 inch rods to the CM4221's reflector. Then you could reclaim a lot of your attic space, heh.

Well I'm not too concerned about Channel 11 but I definitely don't want to lose ABC. I'll swing my antenna south and see what it picks up, if anything. I'm on a hill which does help my reception. I'm in a neighborhood with a property owners association so a roof antenna would result in a huge fight from them.

Thanks for the advice so far, I will post an update on my findings.

hayj

11-19-09, 03:55 PM

I'm in a neighborhood with a property owners association so a roof antenna would result in a huge fight from them.

It probably won't be too huge of a fight when you tell them it's against the law to keep you from putting an antenna on the roof. They don't have the right to stop you.

300ohm

11-19-09, 04:29 PM

Well I'm not too concerned about Channel 11 but I definitely don't want to lose ABC.
Well that even simplifies matters. At a 53.4 NM, the CM4221 may even pick up your channels 7 and 13 as is. With a couple of 36" rods (or door/carpet threasholds or other 36" pieces of metal) horizontally strapped to its reflector, its pretty well guaranteed it will. :)

ctdish

11-19-09, 04:49 PM

He also has a strong channel 13.

IDRick

11-19-09, 05:58 PM

Well that even simplifies matters. At a 53.4 NM, the CM4221 may even pick up your channel 7 as is. With a couple of 36" rods (or door/carpet threasholds or other 36" pieces of metal) horizontally strapped to its reflector, its pretty well guaranteed it will. :)

Interesting comments 300ohm! I want to try this with an mclapp 2-bay (10x9.5) that has a 20" high x 24" wide reflector. It performs very well as a UHF antenna (3 dB less than a 4-bay with reflector). However, high vhf reception on the two bay really takes a hit with a narrow reflector. With that as a preface, where would you mount the rods: 1 each centered behind the elements or some other arrangement?

a8vdeluxe

11-19-09, 07:01 PM

So when is someone going to review the "best indoor antenna every invented by mankind" ?

http://www.avsforum.com/avs-vb/showthread.php?p=17563410

Come on people, what are we waiting for?

link should work now!

300ohm

11-19-09, 07:03 PM

1 each centered behind the elements or some other arrangement?
Yeah. But Im not sure how well the long rods work on all 2 bays. I tried it with a model of the DB2 and the results werent that good. With 4 bays, no problem.

300ohm

11-19-09, 07:05 PM

So when is someone going to review the "best indoor antenna every invented by mankind" ?
Escape Velocity has them reviewed right here :

http://www.avsforum.com/avs-vb/showthread.php?t=1037779

rabbit73

11-19-09, 07:05 PM

a8vdeluxe:
We are waiting for a link that works. Try again.

a8vdeluxe

11-19-09, 07:13 PM

So when is someone going to review "the best indoor antenna every invented by mankind" ?

http://www.avsforum.com/avs-vb/showthread.php?p=17563410

link should work now!

IDRick

11-19-09, 07:59 PM

Yeah. But Im not sure how well the long rods work on all 2 bays. I tried it with a model of the DB2 and the results werent that good. With 4 bays, no problem.

Thanks 300, just looking for your best guess, recognizing that it is guess.

Best,

Rick

IDRick

11-19-09, 08:00 PM

So when is someone going to review "the best indoor antenna every invented by mankind" ?

http://www.avsforum.com/avs-vb/showthread.php?p=17563410

link should work now!

No antenna at your link....

systems2000

11-19-09, 10:48 PM

RickCain2320 (http://www.avsforum.com/avs-vb/member.php?u=8179872),

How many of those analog stations do you want to get? Which stations in particular are you trying to acquire?

Your TVFool data is showing an antenna elevation (AGL - Above Ground Level) of 10'. Is this correct?

With an attic antenna, you're probably not going to get any of the "Tropo" stations.

"2Edge" reception is best accomplished with an exterior antenna and a pre-amplifier that is mounted at least 10' above your roof line.

At 350° (±2°) True, you are getting all the networks there are and most all of your LOS's down to -65.7dBm.

systems2000

11-19-09, 11:06 PM

I've discovered another interesting aspect of my CM3020 setup. When I rotated the antenna (55' AGL) this evening, it affected my portable radio (which was in my office 20' NE of the tower).

This supports the issue I have experienced with the reception off of my other antenna. Is this normal? I was under the impression, that beyond one wavelength, I would not have any interference issues. How do I prevent this from happening to the cut channel antennas I need to install?

300ohm

11-20-09, 09:09 AM

it affected my portable radio (which was in my office 20' NE of the tower).

Which band, AM or FM or SW/other band ? Have you tried moving the portable radio ?

Tower Guy

11-20-09, 10:46 AM

deathnote

11-20-09, 12:19 PM

I'm trying to figure out an antenna to buy for HD.

Here's my tv fool results: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc27b2347973ad

The only channel I care about is ABC channel 9 because it comes in choppy on my direct tv.

Someone on another forum recommended: http://www.amazon.com/Philips-PHDTV1-Silver-Digital-Antenna/dp/B0007XDI54/ref=pd_bbs_sr_1?ie=UTF8&s=electronics&qid=1222980096&sr=8-1

Any advice?

ctdish

11-20-09, 12:41 PM

systems2000

11-20-09, 12:53 PM

Which band, AM or FM or SW/other band ? Have you tried moving the portable radio ?
FM.

I move it all the time. I was just surprised that the CM3020 was affecting another antenna at that distance and now concerned that the antennas I'm looking to mount on the tower are going to be affected.

deathnote

11-20-09, 12:58 PM

Channel 9 is a VHF channel and the Silver Sensor is designed for UHF. An antenna that looks like old fashioned rabbit ears is best for VHF. Since 9 is very strong the rabbit ears will most likely get a strong enough signal but indoor multipath is always a possible and can ruin reception.
John
So, this should work? http://www.bestbuy.com/site/RCA+-+Indoor+Off-Air+HDTV+Antenna/8280834.p?id=1171058630499&skuId=8280834

I want to get something cheap from a local store to try out.

300ohm

11-20-09, 04:28 PM

FM.

I move it all the time.
Hmm, is the FM station pointed in the same direction as the CM3020 is ? If so, since the CM3020 is a UHF/VHF/FM antenna, you could tap into it for additional gain.

ctdish

11-20-09, 05:01 PM

So, this should work? http://www.bestbuy.com/site/RCA+-+Indoor+Off-Air+HDTV+Antenna/8280834.p?id=1171058630499&skuId=8280834

I want to get something cheap from a local store to try out.

For an indoor channel 9 antenna it is probably as good as any small antenna. Your signals are probably strong enough for it to work on UHF channels. For $9 it is not a big investment. The silver sensor would reduce multipath on UHF and and get more signal.
John

systems2000

11-20-09, 05:35 PM

Hmm, is the FM station pointed in the same direction as the CM3020 is ? If so, since the CM3020 is a UHF/VHF/FM antenna, you could tap into it for additional gain.
I'm not looking to tap into the CM3020, I'm trying to discover why it is throwing out such a large/wide interference fiield. I don't need more issues with my reception and I definitely don't need the CM3020 limiting the reception capabilities of my cut channel antennas.

I already have a dedicated FM antenna (on the far side of the house), which feeds the audio tuner.

Tower Guy

11-20-09, 07:00 PM

For an indoor channel 9 antenna it is probably as good as any small antenna. Your signals are probably strong enough for it to work on UHF channels. For $9 it is not a big investment. The silver sensor would reduce multipath on UHF and and get more signal.
John

Agreed. I don't like indoor antennas, but that is the right one for VHF stations.

dr1394

11-21-09, 10:31 PM

cpcat

11-22-09, 07:50 AM

If I were actively fiddling with it at this point I might try it, but I'll probably just leave it as it is for now.:)

Splicer010

11-22-09, 12:12 PM

Wow. Thats a setup you've got there. I am surprised that as nice as the setup is, that you wired it so haphazardly.

ProjectSHO89

11-22-09, 12:35 PM

I would have just gotten the chainsaw....

rabbit73

11-22-09, 12:49 PM

Or raised it a little higher.....

cpcat

11-22-09, 01:46 PM

Tough crowd. :)

rabbit73

11-22-09, 03:10 PM

But it IS an impressive antenna array!

Larry Kenney

11-22-09, 07:01 PM

Very impressive array, cpcat! How much gain do you get out of that top arrangement?

Larry
SF

cpcat

11-22-09, 07:34 PM

Here's the gain graph for the Triax Unix 100A. It's band specific for uhf 14-38 (UK channels 21-40). The graph on the left is the 100A:
http://alpha.future.ee/triax_unix.png

Theoretically, the gain would approach +6db over that of a single antenna. I'd estimate based on the graph somewhere around 19dbi at channel 14 maybe up to around 22dbi at channel 36. It starts to drop off steeply above channel 40. The horizontal beamwidth is very narrow as you'd expect at around 1/4 that of a single antenna .

Don F.

11-28-09, 05:20 PM

I am getting the bug to combine two xg91s to try to improve my signals from Atlanta some 80 air miles way. Presently I use a single xg91 for uhf and plan to install another fairly soon, but need some help on a good combiner. I am removing my ya1713, as I have not been able to receive a usuable signal from WXIA dt 10, and could use the antenna else where.
After combing the the uhf s they would connect to a cm7777, which has been in use with my current setup... I looked at Solid Signal, but the only thing I saw had a 3.5 db reduction in gain..
Thanks for any help...

scottmo2020

11-29-09, 08:19 PM

I am having major problems receiving VHF OTA, which is not a big surprise considering the many issues already brought up with digital TV on VHF. Here is a quick run down and I am hoping for any ideas!

My TV Fool:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc273f8529f405

I have a Channelmaster 4228 (old version) with a Wineguard AP-8275 preamp to receive KOLR on VHF 10 (UHF is great!) I get about 80-84% signal strength, but I have so much interference from something it is not watchable. I am also trying for KRCG VHF 12 with a Wineguard YA 1713 and Wineguard 3700 VHF only preamp (not at the same time). KRCG comes in 90%+ but is also unwatchable with interference. Even KOMU comes in at 80%. Most of the time the signal is jumping all over the place though, and I think I am getting outside electrical interference.

I connected my system direct to a TV testing in the garage, and turned all of my circuit breakers off except for the one in the garage and the interference was still there. Also, when it rains outside my interference seems to go away and all VHF stations are pretty solid. It leads me to think it is something electrical outside. I am going to see the power company and see if they will help me.

I also have a 10kw FM station 1.1 miles from me and used the FM traps on the preamps, and separate FM traps. I have had this setup for over a year though and have not had trouble except for the past few weeks.

I guess the short version of my question, is there something that can filter out that kind of noise? I already have the ground block on my coax and such. I am using two different antennas, preamps, feedlines, and pointed nearly 180 degrees different, and the antennas are in two different locations about 30 feet apart. I might just be out of luck but I'm open to any ideas.

Thank you!

rabbit73

11-29-09, 09:21 PM

scottmo2020:
Your tvfool link doesn't work; it only takes us to the start page rather than your report page. Please try again and use the link in bold type near the top of the report page.
I connected my system direct to a TV testing in the garage, and turned all of my circuit breakers off except for the one in the garage and the interference was still there. Also, when it rains outside my interference seems to go away and all VHF stations are pretty solid. It leads me to think it is something electrical outside. I am going to see the power company and see if they will help me.
It sounds like power line noise.
I guess the short version of my question, is there something that can filter out that kind of noise?Since the noise exists on the channel, anything that filters out the noise will also filter out the signal. It must be eliminated at the source.
Is there any way I can hunt down the source of the interference? I don't know if it is in my house, but I don't think so. No new gadgets, appliances, fluorescent lights, any of that. I mentioned before it seems to get better when it rains. Maybe the electric company could help? I'm afraid I am pretty much out of luck for CBS OTA.The ideal tool would be a spectrum analyzer, but they are expensive and not many people have one. It would allow you to see the signals and the noise at your problem frequencies. You can track down the noise using a portable receiver that can be set for AM and will tune the VHF band. A handheld directional antenna could be connected to the receiver and aimed at the suspected areas. This is called DF (direction finding). Do you know any hams that could help you?

If the interference is coming from the power lines, the power company is responsible for fixing it because you are probably not the only person who is being affected. The FCC says that they cannot charge you for fixing it. It is also a safety and reliability issue so the power company should want to fix it in the first place. It's usually caused by bad "hardware." Don't try to fix it yourself or go banging on power poles if you think you have located the power line source of the noise.

scottmo2020

11-29-09, 09:30 PM

rabbit73

11-29-09, 10:05 PM

dr1394

11-29-09, 10:19 PM

scottmo2020

11-29-09, 10:21 PM

That's better, Scott. If you had used exact address (which doesn't show in the result) or coordinates (the last digits are deleted) the report would have been more accurate, but that might not matter too much if you are out in the country.

At -54.1 dBm KOLR is quite strong, so your interference must be severe. KRCG, at -73.2 dBm and 1edge is a lot weaker.

I assume that your antennas are outside, rather than in an attic.

I used your zip code to generate an fmfool report, which is in the attachment. KCVO is very strong. Lately, some people have been troubled by the second harmonic (2x the FM frequency) of FM signals which fall in the VHF-hi band that an FM filter doesn't always eliminate.

Hi,
Thanks a lot for your help. I updated my TVFool using my coordinates from my GPS. The results seem strange because KYTV I can receive around 80%, KSFX is 92% and KSPR is around 90%, but the report shows they should be pretty weak.

I am down in a hole somewhat, about 100 feet below my surroundings to the southwest where my Springfield MO stations are. GPS shows me at 780 feet, and the antenna is on a 5 foot pole on the 2nd story of my house outside.

That radio station is very strong, because I hear it bleed on my cheaper FM boombox and kids portable radios. But that station has been around awhile and I have just started having problems in the last few weeks.

I'm going to call the power company and see what they can do. I am a amateur radio operator and know a couple people who might be able to help!

Thanks again
Scott

Tower Guy

11-30-09, 08:26 AM

It leads me to think it is something electrical outside. I am going to see the power company and see if they will help me.

You can verify electrical interference with your AM car radio. Start when it's light out. (to avoid skip) Tune to an unused spot on the low end of the dial. (530-600) Drive near your house. If you hear a loud buzzing, you have proven power line noise.

kevm14

11-30-09, 02:12 PM

I'm back.

After living with the WG HDP-269 preamp for a while I am mostly doing well, but still having troubling variations in reception quality on some stations, with one station still being a big nuisance to receive well.

As a refresher, here (http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc272da42d1d2d) is my TV Fool. The station that is being the biggest pain is WSBK RF 39. I regularly get 2 channels below this one in predicted signal strength and sometimes 3.

I was thinking about things that could be hurting me after reading Antenna Basics (http://www.hdtvprimer.com/ANTENNAS/basics.html). I will try the AM radio trick for power line interference. I also can't shake the idea that strong FM stations (http://kevinallenmoore.com/photo/v/misc/ATSC/Radar-FM.png.html?g2_imageViewsIndex=1) could degrade the performance of the pre-amp. I even briefly considered stacking another antenna (I have a WG 7697P).

The other thing I was refreshed on after reading the Antenna Basics page, is the idea that I want to compensate for my cable loss plus another 10dB, I guess to minimize the receiver's AGC compensation. With my WG HDP-269, which specializes in high dynamic range but has less gain than the stalwart CM 7777, I am wondering if I should try another pre-amp. I have about 70 feet of quad shield RG-6, so I estimate my average loss to be around 3dB. The HDP-269 is 12 dB with 3dB noise, so I am right around 9dB after cable losses. Would the CM 7777 work better for me?