The Official AVS Antenna and Related Hardware Topic! - Page 276

Fol. is a comprehensive indoor antenna test report:
http://www.ricability-digitaltv.org.uk/test-reports.htm
Many of the (Chinese made) antennas probably have a U.S. "brand name" equivalent.
Also note many do not have rabbit ears for VHF.
There is no clear "winner" as to whether one style of design is
inherently better than another....individual design seems more important.

Highly rated, non-amplified Silver Sensor was in the middle of the pack....
but they didn't test the amplified model...which now includes rabbit ears for VHF:
http://www.beachaudio.com/Philips/Ph...CID=C12585x003

They also didn't test a simple bow-tie (no doubt worse than a big loop)...and no VHF.

=========================
Amplified antennas tend to be better, mostly because the designer can try to
minimize VSWR problems....presuming you aren't "too close" to a nearby tower.

Among non-amplified models, those with a "tuning knob" to tweak VSWR probably
have somewhat better performance...but are very inconvenient....

The Silver Sensor has deeper nulls that can be positioned to minimize multipath
and would be my preference vs a Loop...which picks up multipath interference
because, unfortunately, it's BI-DIRECTIONAL:
http://www.dielectric.com/broadcast/...ntennas%20.pdf
https://secure.connect.pbs.org/confe...ns/TC05_43.htm

Zip file below contains spread sheets showing detailed VHF and UHF gain
improvement for Silver Sensor vs RCA Loop/Rabbit Ears.

 

Kerry Cozad's Antenna Gain Measurements.zip 34.7626953125k . file

Some on-air comparison tests:
http://www.hdtvexpert.com/pages/antin.htm
http://www.hdtvmagazine.com/archives/8vsbcbstst.html

Recent antenna lab test reported at NAB2008:
http://www.walb.com/Global/story.asp?S=8346127
Includes unamplified (UHF Only) Silver Sensor, but does not
include amplified Silver Sensor with VHF Rabbit Ears.
Measured Noise Figure for some amplified antennas...
but doesn't list important F/B Ratio for multipath suppression.

UK Indoor Aerial Measurements Report (Issue 1.0):
http://www.dtg.org.uk/publications/books.html
Unfortunately no brand names....guess which (periodic) is Silver Sensor....
Some of these are very poor....some amplified models even oscillate....

========================================
It should be obvious that indoor antennas are inherently
low performance, suitable mostly for short range reception.

If it isn't enough, consider a 2-Bay, 4-Bay or even 8-Bay antenna.
[I have an 8-Bay in an upstairs closet.]

Smart Antenna technology also may provide improved performance.

The linked articles were very helpful. I'm in a suburban condo location in hilly Seattle near the airport, 11 to 23 miles from transmitters located in five distinct directions around my home. I've had middling experiences with several indoor aerials, including the Silver Sensor. I also tried a Channel Master 4221 indoors but it's just too big to use in a small condo home where my DTV channels are located in different locations.

Later this summer I may work with my fellow condo owners at putting up a rooftop aerial - complicated by the knowledge that three of my DTV channels revert to UHF in February 2009. I'll also look into Smart Antennas when they show up on the market. In the meantime, I have to report that out of fifteen different indoor antennas I've tried here - some amplified, but most nonamplified, not much of a clear consensus.

Thank you very much for the articles and information.

I'm looking for a UHF DA (distribution amp) with a very high input level capability to use in a mixed signal enviroment. VHF is a non issue.
I have a mix of very strong and very weak signals in the same direction, hence the problem. It's been partially solved, but I'm looking for more leeway.

Preamps are pretty much out for two reasons;
1. The inability of being able to handle high signal levels and
2. The need to have it indoors since I have traps (filters) installed in an attic to tame those stronger signals and have no need to have a remote PS.

I see this Winegard HD269 preamp was mentioned;
http://www.audio-video-connection.com/product/HDP-269

But again, I really don't want or need a two piece preamp (with an additional two F ports and the additional related signal loss to deal with.
The DA I have now is a now discontinued Winegard DA-1018 which is good, far better than a Blonder Tongue MUVB-25 it replaced, but I'm hoping that something better is available.

I have a Pico-Macom TA-36 that's never been used if you can use it.PM me.

As in this;
http://www.mjsales.net/items.asp?Fam...=273&Cat2ID=75

Thanks for the offer, but the gain is way too high and the input level is way too low. Even the TA-12 isn't that great;
http://www.picomacom.com/specs/pico/B/B13.pdf

Amps with that high gain usually have low input capibility.

channelvision cvt-15pia

http://www.channelvision.com/pdf/pro...T15PIA-ins.pdf

The lowest noise figure in-line amp I've come across. I use it as a post-amplifier indoors after a 20db gain research comms amp on the mast. No problems with overload in my configuration. Gain is 15db.

Several times I've posted results of various on-air tests which found Indoor Loss
(using same antenna) was about 13 dB (+/- 7 dB):
http://www.avsforum.com/avs-vb/showthread.php?p=7892248
http://www.avsforum.com/avs-vb/showthread.php?p=7891979

Bob Chase's attic was at high end of this range...very little due to loss of height:
http://www.avsforum.com/avs-vb/showthread.php?p=7839036
Indoor Loss and Antenna Height Gain are somewhat intertwined...higher is better....

Here's a test from U.K. comparing UHF Silver Sensor indoors vs hi-gain outdoor antenna:
http://www.megalithia.com/elect/aerialsite/settop.html

I have an xg91 with a channel master 7775 amplifier connected with old DirecTV cable about 100 ft long, but I only need about 25 feet, up on a 1 story roof which is overhung by a massive oak tree. Antenna is approximately 25 ft off the ground attached to the chimney and a large tin roof covers the whole house. I have a treeline about 50 yards out and Pecan trees left and right with a small window towards the towers which are all together within 4 degrees most of them are at 45 miles, a couple closer to 25 miles. Flat marsh land and open ocean between me and the towers.

Im not happy with the reception. I get frequent drop outs sometimes.

What can I do to improve this setup?

Im thinking a shorter cable for the run, which may be in better condition as well. What type of cable should I look into?

I'd like to start off by thanking everyone in this thread.

The information that has been posted has been extremely valuable. I've only just recently started to dabble in Over the Air digital television reception and without this thread, I doubt I would have even been inspired to even consider a do-it-yourself homemade antenna project.

Needless to say, like many others, I have been amazed at some of the results I have gotten so far up to this point.

So far, I have built a number of antennas. I haven't given all of them serious testing. The ones I am having somewhat problems with, I will get to later on and I am hoping others may have some suggestions. That is even if the ideas will work at all.

Below is a photo of the VHF/UHF attic antenna. It pulls in most digital signals, but there are problems on a few stations (Analog reception is fine on all channels except for a very slight ghost on CBS 2, but it is not very annoying). I was going to buy a pre-amp but then I stumbled on the do-it-yourself antenna thread and decided to give that a shot first.




Here is the TV Fool information on available channels......





There were big problems with the digital signals from PBS Channel 13 and CBS Channel 2. They would be weak at many times and pixelate an awful lot.

I built two antennas. A homemade DB4 and a homemade DB8. The DB4 increased performance and I didn't seem to get any noticeable increase in performance from the DB8 that I built (The DB8 was not built with a reflector screen because the DB4 actually performed worse when tested with a reflector screen).

Below are several pictures of the DB4 clone currently installed in the attic.....







The performance of this DB4 clone has been outstanding until this past month. I even pick up CBS from Philadelphia. However, since some nearby trees have grown in recently, there have been a few problems with a couple of stations.

Basically the primary problems are back to being CBS 2 and PBS 13. The signal on some other channels seems to have gone lower, but the picture is still good and crystal clear..... And that is without even going through a splitter.

I'm sure a pre-amp may be in my future, but I put together a few other antennas maybe thinking that could be avoided.

I built a Gray-Hoverman and put together a few other antennas. I'll discuss them and show pictures in my next post.

Continued.........

I need to make this useless post on the board before I can make further posts.

More on the antennas coming next.....

Thats a sweet 4 bow tie antenna TVNY.

Here are some other antennas I built and put together..........

I built a Gray-Hoverman and I was surprised at the performance I was getting on channels that I previously had problems. However, with this antenna I had problems with other channels. That problem may disappear when all channels are changed in February 2009. I can't say for sure.




One of the best antennas I built was a DB4 clone that could be installed near the television. I put it on a wooden stand......







Sitting on bench after being built... click here...


There are some antennas with parabolic screens that I plan on testing....

This one seems to be promising... but I'm not sure....



For a larger image, click here...


I was wondering what others thought about parabolic reflector screens for antennas.

I had a few parabolic antennas in the garage from the old days when HBO was broadcast over the air (It was on microwave frequencies back then and required down converters).

I'm curious as to if a DB2 can be used as a feed horn. I'd also like to know the optimal length of the feed horn from the parabolic elements of possible.

I don't even know if this is feasible. That is why I would like to know what others have to say.

Here is another possible antenna design with a 24db parabolic screen designed for "wireless cable".............




Another angle here.......





I think these parabolic reflector ideas may have something to them, but there are so many variables.

Does anyone else have any ideas regarding their use?

Thanks bro.

RG6 would be fine.

If you have D* and aren't using the H20-600 you should be. The OTA tuner is excellent.

cpcat; What kind of signal levels are you talking about? That is another example where the input level isn't specified (which doesn't help me in this case).
How close s the nearest xmitter tou your location?
Not to me Rick.
In spite of what you think about my current Winegard DA-1018, it does work and far better than what it replaced (BT MUVB-25). I'm just looking for a little more edge, but I don't want to take a step backwards. Can that amp be powered from internally w/o going through the coax?

Unfortunately, I couldn't find any max input level specs for the cvt-15pia. I'm at >65 miles to most of my transmitters but do have a full power PBS at around 45miles and a full power religious channel at 40 as well as full power CBS at 50. I use the hi port of an HLSJ at the antenna right before the RC amp so local FM is virtually eliminated. I'm also using a Blonder Tongue mwt-u notch filter set to trap the local analog religious channel right before the cvt-15. Finally, I use a variable attenuator after the cvt-15 and right before my tuners to tweak the final input level as "wide open" I still get a little overload at the tuner (not the amp).

I wouldn't worry about the loss of a power inserter if I were you either way. I use an HLSJ to insert power wherever possible as I don't need/want any lowband or FM. This means placing the HLSJ after the amp, attaching the DC power source to the "low", the "common" to the amp output, and the "hi" to the tuner. You could also put another UVSJ or HLSJ on the amp's input if you want to prefilter the signal further. You could alternatively use a UVSJ as the power inserter after the amp similar to above assuming DC is passed on its vhf side.

Looking at the HDP-269 specs, it may be a better choice for strong signal environments than the cvt-15.

A parabolic reflector is best for a single frequency. For a wider bandwidth, commercial antennas have their reflectors at a 90 degree angle.

Nice workmanship.

For parabolas, the elements need to be placed at the focal point. You will need to know the radius of the reflector bend. Google for the formula of the focal point of an elipse. But that reflector you have is too small for effective parabola performance, it will act more like a regular reflector. Commercial uhf TV parabolas were/are 5 to 7 feet in diameter.

Both the Hoverman and Bow-ties dont really come into their own without a reflector. For the Hoverman flat reflector it should be 100mm, plus or minus 15mm. Also I noticed you used the old 44mm element feed spacing. Recent modeling tests have shown 95mm will increase gain. Check the Hoverman thread at http://www.digitalhome.ca/forum/show...=81982&page=33

For the bow-ties check the How-to-build-uhf antenna thread http://www.avsforum.com/avs-vb/showt...798265&page=10 With mclapps 15 inch reflector spacing, you may be able to get channel 8.

Both the Hoverman and 4 bay bowties will out perform the uhf section of that commercial vhf/uhf combo. But I noticed you have a real channel 8 digitial at -53.4. The vhf/uhf combo will be superior for that channel. After next February, how many stations will you have on vhf-high and vhf-low ?

This was a good read, thanks. As it states, you can't get something from nothing. In other words amplifying a bad signal is not likely to help. Amps add no directionality, or real gain.

Those "contract aerials" seem to be quite popular in the UK, but I'd imagine they would work just fine in many areas of the US (paired with a VHF antenna). They seem to avoid bow-ties, however, for reasons still unknown to me.

I think Im gonna try a Winegard 4400, in place of the xg91. I put a DB2 up there and it seems to be holding its own against the xg91.

Scratches head.

When aiming the xg91, I was getting better reception moving towards the eastern trees that frame the shot towards the towers in Charleston, until I ran into them, then it dropped again, so Im hard up against the Eastern trees, just off of them. Ill take a compass up there and check, Antennaweb has the towers at 62 to 65 degrees magnetic north.


How do I get my tvfool image to this message board?

First, if you haven't already done so, save the image to your hard disk. On the tvfool results page, you should be able to just click on the image and a menu pops up with an option to save it.

Then, when you post a message here, at the bottom of your message-composition page you should see a box "Attach Files" with a button named "Manage Attachments". Click that button, and you'll get another window where you can navigate to your saved image and upload it.

Here it is.

Im concerned with the first 8 channels listed minus channel 19. They are all clustered in the same direction (and location), excepting for channel 16.1 WJWJ PBS which I am picking up fine on the backside. I am having particular trouble with 36.1, 4.1, and 7.1 in that order.

I could conceivably move an antenna into the giant oak tree(dont really like this idea), or to another location on the roof.

When it comes to Antenna making, you are better at just purchasing them. For your so-called, 24dB gain parabolic, I would say you need some more tweaking. Let's not forgot about VSWR's. These can kill your radio.

For $50, I would just buy a mass produced model.

1. I have 7 traps,
2. 18db isn't a 'high' gain amp. That 36db that the other poster mentioned is.
3. I'm feeding four tuners. I need the gain to make up for that loss and the low signal coming in.
You do realize that I'm dealing with three stations with 45-50 dbmV signal levels (analog) and four more with levels between 30-35 dbmV (digital)? Then consider that I'm looking at signals I can't even measure (less than -35 dbmV).

cpcat; You have nothing even remotely close to you, so there isn't anyway you would be bothered with overload.

You might want to read that again, he said it was a parabolic from a 24db wireless cable set-up. I don't think he was claiming his antenna was making 24 db.

It looks like He's having fun with it and probably learning more about antennas along the way.

VSWR's might kill your signal to the receiver but they won't kill your receiver, it will damage a transmitter though.

Published amplifier input specs are of only limited usefulness in selecting one to meet an individuals' needs for a number of reasons.

First of all, with many consumer products, especially Winegard and Channel Master, they seem to have just taken old figures of arbitrary limits for keeping sync compression or intermodulation distortion developed by analog signal inputs under certain thresholds, but use them as limits for contemporary applications. Second, often times the input specs don't even say what channel load they apply to.

It is common practice among newcomers to the residential antenna amplifier manufacturing market to specify a level at which some kind of intermodulation distortion is developed. Some manufacturers actually say it is the 3rd Order IMD level, others just say IMD. As I understand it, an intermodulation distortion benchmark, if properly used, is the input (or output) level at which a single digital channel develops some undesired, on-channel intermodulation byproduct that is 40 dB below the signal (-40dBc) on itself. I have also read in a report linked way back in this thread somewhere that when a signal develops -40dBc of 3rd Order IMD on itself, it tends to develop -52dBc of 3rd Order IMD on adjacent channels, so that tells me that when I am trying to process my local Baltimore channels 38 and 40, but am plagued by a much nearer and stronger Washington DC channel 39 that is commonly nearly 20dB stronger than channels 38 and 40, that the intermodulation developed will excessively degrade the channel 38 and 40 signals before it reaches the -40dBc overload spec.

When you put different frequency signals into an amplifier and they also are at different signal strengths, it is impossible to calculate all of the undesirable intermodulation byproducts that are developed, but certain of the weaker signals will fall victim to the debilitating effects of that distortion. And making matters worse is that the tuner may get swamped by the stronger out-of-band signals as well.

I don't know Videobruce's situation, but if he has seven filters in series before his antenna signal hits his amp, he may have so much insertion loss that the biggest problem that his weakest signals face is that the cumulative insertion loss may be dropping his weak signals too close to the thermal noise level. Does he have a real signal meter, such that he can report his actual signal levels in dBmV both before they enter his filtering network and after?

FWIW, I bought a couple of inexpensive Channel Master OSD0065 23dB UHF/16dB VHF preamps and compared their effect on some a very weak analog channel 24 and digital channel 59 signals to that of an uncommon Winegard item, its model AP4747, which is a 23dB gain UHF preamp that is nearly identical to the AP4700 and AP4800 and should have the same maximum output of those two products. I had a couple of 20dBmV analog inputs and a couple of 10 dBmV digital inputs as my strongest signals, but my weak inputs were an analog channel 24 that was around -5 dBmV, and the digital channel 59 was, as I recall, perhaps around -25 to -30dBmV.

The UHF gain was 23dB in all four amplifiers tested, as specified, which actually surprised me because the gain of a Winegard AP4800 is actually 36-38dB at about 500-530 MHz, whereas it is about 28dB at around 700 MHz, but the AP4747 gain was flat across the entirre UHF band.

The manufacturer's published maximum output figures for the AP4700 and AP4800 exceed those of the Channel Master OSD0065 by about ten dB, yet the Winegard preamp visibly decimated the weak analog signal and degraded the weak digital signal such that the primitive "%" signal meter in my set top box deemed it to be inferior, while the Channel Master preamp sustained the analog picture quality and the digital signal "%" went up just a little. And my input and output levels were well below the rated maximum signal levels for either product.

I can rule out the possibility that the Winegard signal processing problems were caused by out-of-band tuner overload because I then hand-tuned a UHF bandpass filter and put it on the preamp outputs, but that did not improve the Winegard's performance. I was able to improve the Winegard AP4747's performance somewhat by placing the tuned BPF on its input, but that was a poor solution because the BPF had about 4dB of insertion loss, and I couldn't sacrifice that much input, as that additional antenna signal loss would render my system vulnerable to atmospheric signal fade.

Well, of course one could just buy the antenna .. but thats not the fun
of the whole process for the experimenter. One gets a kick modeling
and tinkering with these things and using the knowledge in your own
head to sometimes even surpaass whats available on the market..
Durability .. thats another issue.


John