The Official AVS Antenna and Related Hardware Topic! - Page 202

Thanks for providing this!

I have limited space in my attic for a 3rd UHF only antenna that I'm trying to use to pick up a single station. My goal is to mount it above my 4228 pointing in the opposite direction - thus It can't be very tall or long.

From looking at your chart I have a couple questions:

1) The DB8 is listed at 14.0 dBd while the CM 4228 is at 11.9 - I have a hard time beliving there is that much difference between two VERY similar antennas - do 4 separate reflectors really help?

2) The Blonder Tongue BTY-UHF-BB would seem to be the pick for a compact UHF antenna at 10.2 dBd and only 24" - but is it really this good? Obviously the price is beyond reason, but I can't imagine why other manufacturers wouldn't build a similar antenna if they can get this much gain from this small of a size - there are many far larger antennas with less gain.

Right now the 43XG would seem to be the best for the size (at 39" it is as large as I can fit) - but I'm a bit dubious about the numbers given the abnormally high DB8 numbers.

Any other suggestions for a compact UHF attic antenna?

Thanks!

The gain of the Blonder Tongue UHF BB is unremarkable. Blonder Tongue reference its gain figures to "isotropic" rather than to "tuned dipole", so you would have to subtract 2.2 from it to compare it to most other publiched gain specs. You can buy something for $30 that is a foot or two longer with the same gain.

I have installed over half a dozen of them. They are designed for durability rather than for extraordinary performance. You would be wasting your money using one in an attic unless you are incredibly cramped. I only use them on highrise buildings

The likelihood of a dB of improvement in published gain figures will discernibly improve your reception is slim, at best.

cpcat,
I use four CM 4248 stacked 2 0ver 2 with about 40 inch spacing. They are connected to a Lindsa 4WCU and Research Comm preamp. The preamp provided a noticable improvement over the AP 4700 it replaced. I measured the loss of a few of the small 2 and 4 port splitter/combiners by going through two so I had a single port at each end. This showed about a 5dB loss indicating a 2.5 dB loss for each one.
Hopefully you used four exactly equal lengths of cable to connect the antennas to the combiner.
With the pairs of mismatched antennas you might try putting similar antennas above each other. The phase mismatch will show up as a response peak slightly off the center of the expected pointing direction. If it is not too large reaiming the rotator will find the peak with little loss of total gain.
John

what did you use for screen and how did you attach it.

with the 91xg would you cover the entire screen or partial as you did?

please explain.

I did make them all identical by interchanging the reflectors i.e. each antenna had a small and a large reflector. In fact, this is how I did the majority of the testing with the H-quad. The phase seemed correct on some channels but not on others and this seemed to vary among channels with spacing. It's possible I suppose that I have a defective 4WCU.

I'd be interested in how your performance would compare if you did a stack of stacks instead of a quad.

The Research Comm. 9253, 9252, as well as the Televes ref. 5006 and Sitco PA24 all outperform the CM 7777 for uhf in my experience. I've not used the Winegard AP 4700 so can't comment on that one.

1/2 inch chicken wire (available at Lowe's) fixed with plastic wire ties to each top and bottom reflector.

I covered the entire back except for the top and bottom most space of the earlier vintage DAT 75 with the small reflector and the same area of the larger one to cut down some on wind load.

The XG's reflector is even a little smaller than the earlier DAT75's so I'd probably just cover it entirely. OTOH, the XG's is already a mesh-type so it may not help as much.

What is the purpose of the wire cage material on one side of CM 4221/4228 and DB2/4/8 antennas?

What happens if I remove it?

Thanks.

It's there to block signals coming from the back. If you remove it, the antenna will become more bidirectional. Usually this is a disadvantage unless you have a specific reason for allowing a signal in from the back.

Multipath is caused by signals being received by the antenna from different directions--and hence with different arrival times.
Digital receivers have a very limited tolerance to multipath, esp. when the various signals are more or less the same signal strength.

Antennas maximize gain in the desired direction by minimizing gain in undesired directions.
The reflector screen attenuates the usually strongest multipath signal, which occurs when the signal reflects
back off of buildings and hills slightly further along the signal path than your antenna.

Think of a flashlight reflecting off of an all-glass high-rise into the "back' of your antenna....
vice glancing reflections from buildings and hills off to the side of the direct signal path....

If you have signals coming from opposite directions, taking the screen off can help to receive signals
on the former "back" of the antenna....although with a lower (-3 dB) gain towards the "front"....

This will also receive a lot more multipath...which may or may not be tolerable, depending on topography, geometry, et. al......
So, as usual, it's pretty much trial and error...

Just to follow up on this again, I did buy the GEMDTV-1 and tried it out though I eventually returned it. In my side by side informal comparison I found that the GEMDTV was comparable to the silver sensor and the U75R was superior to both. The size of the GEMDTV was compact enough to mount in the drop ceiling, but the multipath was significant enough to compromise performance. In the end I went with the U75R in the attic which is perfect (until 2009 anyway when I will need VHF).

Thanks for the comments.

Thanks for the explanation. My dad lives at about 120 degrees between tower farms, so I have tried tweaking his antenna to receive both signal with mediocre sucess.

However, for the bowl games, I had to go on the roof and peak for CBS for the Gator and then go back up to peak for the Rose and the rest of the BCS games. He will watch Saturday's NBC games in SD.

So my options are a joiner, which will be hard given how the channels are, just combining 2 antennas and seeing what happens or removing all or part of the screen on his DB4.

Thanks for the help holl_ands. I happened to be at a local Menards looking for something else when I saw their antenna selection & that they carried the Philips MANT950 antenna for $80, so I figured I'd pickit up & see what it'd do. Almost as an afterthought I picked up the MANT510 indoor setup amplified antenna for $22 too, figured I'd just give it a shot, who knows, I could return it later.

I got the 950 ouit & just held it up inside, near the roof, & was happy to see that that it got all the channels in my list quite. But while I was at it I got out the MANT510 too and ... wow. All the channels I wanted came in quite clearly except one, just from this little indoor unit sitting on top of my entertainment center, without any real fiddling. Been using it a couple days with no complaints. As a reminder here is my antennaweb output again:


Odd that I got 32.1 (violet) quite strongly, but I could only get 14.1 (green) intermittently & only with careful alignment of MANT950 (not at all with MANT510). All the rest were good reception with either. I don't care much about the 14.1 CW channel, so I'm planning to go the way of simplicity and low cost & keep the MANT510

I have a cable line (which broadcasts 20 or so unscrambled channels, which i don't pay for) leading upto my apartment and an HD antenna. unfortunately i have brick walls and can only run the existing coax through the wall. I tried to mix the lines together with a combiner/mixer (from radio shack). this didn't work for i thought it would (i only recieve the cable broadcast and the HD signal says no/weak). when i unplug the cable line from the combiner (and run it just with the HD antanna in) the HD signal to the TV is fine. this suggests to me that the cable line is overpowering the antenna line. is this right?
any suggestions? do i actually have to have two lines coming into the house?
Thank you

Cable and antenna signals are in the same frequency band so there is no way to combine them. You need separate cables for each of them.

Hello all, first post here...

I live in Murrieta california, it is like 65 miles from the Los Angeles signals being shot of Mt Wilson. According to antennaweb, I do not see any DT channels for my address-well there is one in san bernadino, pbsdt.

I put a channelmaster 4228 on roof just to try before I went and bought a preamp, mast, etc....all I get is snowy old school channels and that one pbsDT channel. My house is right behind a slope, and above that guy is another slope, then 3 miles away is a little mountain range.

I have heard of a couple people getting signal in my town, but I think my area might be the worst? Is there any hope to get OTA HD here? or do I have to get it through my directv (barf)

Thanks in advance

Craig in Murrieta

First go to antennaweb.org and at the address page, click on the options link and enter an antenna height of 200 or 300 feet or even higher; then select digital stations only. You may not get all those digital stations & the color codes are not that meaningful (not that they are all that accurate to begin with), but this should give you a list of where and what directions the digital stations are.

If you have a slope behind the house, tilt the center aim of the CM 4428 upwards towards the ridge line if you can. The CM 4228 is rather directional and that may pick up the signals refracting across the top of the hill. Also raise or lower the antenna or just move the antenna a few feet if you can, just in case you put it at a local dead spot. Try these steps before getting a pre-amp, although a pre-amp is not likely to make that much difference if you can't get the digital towers on the top of Mt. Wilson at all.

Also, what ATSC tuner are you using? Some tuners are better than others at locking on to marginal signals.

I had to goto 200' in the air till I got one network, CBS, 300' finally got me all the networks, ktladt, fox, etc....

Looks like I am screwed for OTA eh? as I am not putting a 300' mast up
Thanks

Although the DB-8, CM4228 and WG PR8800 appear to be very similar 8-Bay antennas,
the feed structures and reflector screens are electrically quite different.

It is frequently difficult to determine whether a manufacturer is specifying "typical" or "minimum" specs,
i.e. whether it's an average/median value or a guaranteed for 90+ percent of shipped units.
Or perhaps was only measured on the carefully tweaked prototype model....
And sometimes it's difficult to determine whether they used dBd (relative to a dipole)
or the 2.15 dB "inflated" dBi (relative to isotropic) gain measurement units.

CM and Winegard provide very detailed spec sheets with gain, beamwidth and Front/Back Ratio for several UHF channels.

However, Antennas Direct simply claims "15.8 dB gain" for the DB-8, where it is unclear whether this is
in dBd or dBi (2.15 dB higher) units....and whether this is an AVERAGE across the UHF band or (much more likely),
the MAXIMUM gain for the BEST channel....
I determined the "14.0 dB" value for average UHF gain, by converting
15.8 dbi to 13.6 dBd and gave then the benefit of the doubt by simply rounding up to guessitimate the average UHF gain....
I would guess that this is actually MAX vice AVERAGE, so it's probably still overinflated by 2-3 dB...

===================================
I rechecked the "Data UHF NEC + Measured" spread sheet page which contains NEC Simulations results for average UHF gain.
The NEC Sim data points have been updated and provided via downloadable "ants.xls" file since I "eyeballed" data off the charts.
My "eyeballed" CH14 gain numbers were off by quite a bit (too small) with only minor tweaks for other channels.
Updated averages are below.

CM4228, 14.6 dBd measured, 11.3 dBd NEC Sim vs 11.9 dBd "spec"
PR8800, 13.2 dBd measured, 10.0 dBd NEC Sim vs 11.6 dBd "spec"
AD DB-8, unk dBd measured, 11.9 dBd NEC Sim vs 15.8 dB? "spec"
Surely, you can you see which "spec" claim doesn't fit....

Also, if you check www.hdtvprimer/ANTENNAS/comparing.html,
you'll see that the author did not include the (presumably 1-2 dB) loss
in the DB-8's combiner in the NEC model.....

So all of the 8-Bay antennas are "close", with the edge given to the CM4228....
Kerry Cozad measured 1.4 dB MORE average gain across the UHF band for the CM4228 than the PR8800....
which is consistent with NEC Sim.
And actual on-the-air test results generally show that all three 8-Bay antennas are very good,
with the CM4228 having a reportedly small performance (and price) advantage....

BTW: Due to receiving both the direct path and the "ground bounce" signal, Kerry Cozad's model range test data can be
2-3 dB higher than "isotropic", i.e. "free space" gain cited in NEC simulation results and (presumably) also spec sheets.

========================================
Fortunately, Antennas Direct isn't the only source of data on the 43XG:
http://cpc.farnell.com/jsp/endecaSea...sp?SKU=AP00815
http://cpc.farnell.com/jsp/endecaSea...cpc/253268.xml
Probably dBi units (subtract 2.15 to find dBd).

http://www.ceda-antenna.com/index.htm
http://www.funke.nl/
Hmmm, CEDA website seems to be down and Funke is rebuilding theirs...
Guess I'll just attach the data sheet.....
Based on comparison to "simple" antennas, I've determined that Funke uses the inflated dBi units rather than dBd.
And, as is usual with non-U.S. antenna manufacturers, you have to be careful to read the frequencies (in MHz)
and might have to convert their channel numbers into U.S. channel numbers.

 

NL - Funke 43el Bowtie Reflector - 220_140302_dcf4543_230505_790501400.pdf 169.6572265625k . file

Don't use the antenna height at avsforum as gospel. I have to enter 150' at antennaweb for my address to get a list of digital stations that is close to what I get with a CM 4221 in my attic.

But if you have hills blocking the line of sight, that is a problem. Before you give up, try out different aims & locations for the antenna such as I suggested. If there is a high rise building behind you, you could even aim the antenna at the building to see if you might be able to pick up reflected signals off of the building.

I am 95 miles from the LA towers but in a direct line through a mountain pass between 2 10,000 foot peaks. On that same line is a strong DT station 20 miles away.

I also have 3 local stations at 90 degrees, that I get with a Radio Shack HDTV Antenna (Shaped like a DBS dish) which claims 6dB gain and has a 10dB preamp that I will connect with an A-B switch or reverse splitter which ever works..

I had assumed and been advised for the LA stations to get either the 4228 or XG91 along with the 269 12dB Urban Preamp rather than the 7777 because of the 20 mile station and mount the whole thing on the roof.

Over New Years, in order to get the bowl games and Rose Parade on KTLA, I took the RS antenna and stuck it on my deck at floor level behind glass doors pointed at LA, and too my surprise, I get all the LA channels at 65-75% on my sets Signal Strength bar but I do have to shift the antenna sideways 1-2 feet to get the signal on some of them. I tried moving the antenna to other locations on and well off the deck and the roof overhead but never got as good a signal.

Does it make sense that I just happen to have a 4 foot hot spot just at the front side of my house, 4 feet from the ground, and just at the front of a deck which is covered with a 12'x16' aluminum awning? Everything I have read says this should not be. It does have a clear line across a golf course and open desert though with no houses or trees in the way.

So now I am thinking of using a 4228 or its half sized version and standing it just outside the fixed glass door, with the hope that its larger span will gather all the hot spot signals and eliminate the need to shift the antenna 2-3 feet. Assuming a 12 dB gain and a 12 dB amp and 4 db loss for 50' of RG6, that's 20 dB rather than the 10-12 I have now.

Based on this I'm now thinking of dropping the on the roof approach. What would you do if you were me?

thanks - Do you think it would work if i split the line once inside my apartment, and ran one into the cable input and another into the antenna input? or am i completely out of luck?

No, you have to carry the antenna and the cable signals on separate cables all the way.

You can re-center the map by clicking on the desired location. This also re-computes and updates your channel listings. It makes a noticeable difference for me because the default location for my address is a couple hundred yards away and down a slight hill from where my house is actually located.

Hi,
I have an antenna in my attic and there is a run of RG6 quad from it down to the basement which connects into a Channel Plus Model DA-8200HHR distribution unit...and from there I go to 4-5 locations in the house...will this type of setup affect a HD signal differently from analog? My current plan is to use this setup with HD...I am planning on adding a CM 4221 antenna in the attic and then using a CM 538 joiner to combine the two antenna's (the current antenna gets better VHF signals than UHF)..Does this sound reasonable or am I waisting my time...btw the wife will not allow an antenna outside...and I'm not getting rid of her ...

thanks
Doug

I'm currently using a 25' mast for my 4228 do you think its possible to get a better signal if I go higher up on a 50' mast for the weak signals I'm receiving?

Or, of course, installing a rotator.

(it appears that you have an outdoor antenna)

Primary response to your double post is found here:
http://www.avsforum.com/avs-vb/showt...33#post9241533

Your house is probably blocking the nearby TV transmitters so that you have a better chance to receive distant LA stations.
Be sure to try it without the Preamp as well as with it.....

Can you post a brief list of which stations (analog or digital) you are able to receive so we can see
how many local stations are blocking reception from LA???

The proble with a rotator is that the antenna is hooked to a D* HR10 and it has no way to change the direction when it wants to record something.

I need help picking a new antenna. I am at zip code 54726. All my channels are within 40 miles except for 1 channel CBS which is about 60 miles away. Right now all my digital channels broadcast on UHF but come 2009 two channels are switching to VHF. I was considering the 4228 before the two channels are switching. I know the 4228 picks up VHF good but the 1 channel switching is the CBS channel that is going to be on 8.1. The other channel will be on 13.1 and I am sure I would be able to pick it up with that antenna. Will the 4228 pick up a VHF channel from 60 miles away? What other antennas would be a good choice?

I think that you are on the right track. Antennas interact with the ground such that it is possible to gain up to 6 db if the ground slopes at the perfect angle and the antenna is placed at the optimum height.

A basic explaination is here: http://www.hdtvprimer.com/ANTENNAS/siting.html