NYC Area VHF Reception issues - AVS Forum
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Old 12-20-2011, 07:59 AM - Thread Starter
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Hi all,
I've recently cut the cord. I get about 50 channels OTA with (2) Attic mounted antennas. My setup is as follows:

(1) Antennas Direct DB8 UHF
(1) Antennas Direct CLEARSTREAM5 VHF

They are mounted on different J Mounts hanging from beams in the attic. Both are pointed at roughly 92 degrees. These two antennas go into the combiner included with the CLEARSTREAM5. They are then piped into a Winegard ANWI8700 AP Signal Amplifier. The signal is then split with a Monster splitter into two different 50ft coax cables. One goes directly into my living room TV and the other goes into an HDHomeRun.

I've read that these two antennas make an excellent combo.

My TV Fool report:
http://www.tvfool.com/?option=com_wr...4033053978e3be

My TV doesn't have a strength meter on its OTA tuner so I used the HDHomerun Software to check the signal and adjust the antennas. All UHF band channels (anything not 7-13) come in crystal clear; absolutely no issues whatsoever. Channel 7 (ABC [VHF]) still has some artifacts. Before I had the CLEARSTREAM5, I used to get channel 7 on just the DB8. It had more artifacts but I figured that adding a hi band VHF antenna like the CLEARSTREAM5 would improve my signal. It has improved it dramatically. I was previously unable to get channel 11 (CW [VHF]) or channel 13 (PBS [VHF]) before adding the CLEARSTREAM5. Both of these channels come in now. I don't watch them enough to know if they too have artifacts, but I haven't seen any yet.

The channel 7 issues are intermittent and could be something as small as a skip in audio or a couple pixels. It's enough to be annoying.

Here is a screen capture from my HDHomerun Software



Are these in the acceptable range? I think my problem is that every so often, I see the Symbol Quality % drop from 100% to 0%. This seems impossible to me and could just be a flaky cable.

Would this cause the occasional hiccups I see? Is the Signal Quality always being right around 74% a bigger concern? I also wonder if I need a powered splitter. I've read that small artifacts like this could be caused by the splitter. I'm only splitting it once into two different signals.

Also, two things regarding the Wingard Pre Amp.

1.) Would it be better to hook up the Winegard Pre Amp directly to the CLEARSTREAM5 and then into the combiner? I tried this, it didn't seem to make much difference but I'm willing to give it another shot.

2.) The Winegard Pre-amp mast mount isn't big enough to wrap around the J Mount I bought so it kind of floats between the two antennas. I'm wondering if this makes it less effective as it's supposed to be mounted.

I know the most ideal situation is mounting an antenna on the roof but I'd like to avoid that if possible.

Thanks for reading my long post, I appreciate any help you guys could give me!!
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Old 12-20-2011, 08:50 AM
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Quote:
Originally Posted by jubei_nj View Post

The channel 7 issues are intermittent and could be something as small as a skip in audio or a couple pixels. It's enough to be annoying.

I would have first guessed that there is an airplane between you and the tower, but too many are sourced from exactly the same location ... oops.

Your problem sounds like multipath; signal from two different "sourced" add out of phase. Reflections are classic causes ... but why only one channel? You mention less than perfect results from the other high VHF, minimized by the new antenna.

I'd TRY pointing the VHF antenna off-axis, both horizontally and vertically; you might avoid a reflection that occurs from something that is the proper wavelength to reflect 7. The rabbitears.info webmaster, in his new abode, had this multipath problem and used a trashcan to "eliminate" off-axis signals. Take a look at Trip's thread, http://www.avsforum.com/avs-vb/showthread.php?t=1372416

Good luck! Keep us informed.
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Old 12-20-2011, 09:35 AM - Thread Starter
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http://www.silicondust.com/forum/vie...1b207cc213921d

Seems that my drop in symbol quality could be the multipathing you referred to. I'm going to try the antenna on its side. Seems like I'd have this issue even on the roof? If that's the case, it makes me feel better about trying to troubleshoot inside and taking the roof out of the equation. Like I said, my UHF is coming in without any trouble.
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Old 12-20-2011, 09:54 AM
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You might also consider intermittent interference as a possible source of the channel 7 problem.

Possible sources include the usual suspects: FM Radio, two-way radio (taxi, police, etc), or electrical devices such as lights, motors, and the like.

You could try a Pico-Macom HLSJ with the "L" port terminated as a high pass filter to attenuate anything below about 120 MHz. Install it between the C5 and the U/V combiner's VHF input.

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Old 12-20-2011, 10:14 AM - Thread Starter
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Originally Posted by gbynum View Post

I would have first guessed that there is an airplane between you and the tower, but too many are sourced from exactly the same location ... oops.

Your problem sounds like multipath; signal from two different "sourced" add out of phase. Reflections are classic causes ... but why only one channel? You mention less than perfect results from the other high VHF, minimized by the new antenna.

I'd TRY pointing the VHF antenna off-axis, both horizontally and vertically; you might avoid a reflection that occurs from something that is the proper wavelength to reflect 7. The rabbitears.info webmaster, in his new abode, had this multipath problem and used a trashcan to "eliminate" off-axis signals. Take a look at Trip's thread, http://www.avsforum.com/avs-vb/showthread.php?t=1372416

Good luck! Keep us informed.

BTW, when you say "off-axis" do you mean pointing it towards the sky instead of straight? I ask because I felt like my signal got better as I pointed it upwards more. My DB8 is pointed straight ahead.

Also, ADTech, it seems that Pico-Macom HLSJ is no longer sold. Do you know of a website where I could buy that or something similar?

EDIT

Maybe something like this? http://www.solidsignal.com/pview.asp...ce=google_base

And this to terminate:

http://www.solidsignal.com/pview.asp...u=615798303501
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Old 12-20-2011, 10:38 AM
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Just for the heck of it, just try the VHF antenna. Remove the joiner and UHF antenna completely. See if the same thing happens. If it does, try removing the amp completely. Don't just unplug it, bypass it, hook the antenna directly into the tv.
Your tvfool results show an amp might not be needed.
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Old 12-20-2011, 10:39 AM
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Quote:
Originally Posted by jubei_nj View Post

Maybe something like this? http://www.solidsignal.com/pview.asp...ce=google_base

And this to terminate:

http://www.solidsignal.com/pview.asp...u=615798303501

Those are both excellent choices. The Blonder Tongue HLSJ should perform just as well as the Pico Macom.
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Old 12-20-2011, 10:39 AM - Thread Starter
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Quote:
Originally Posted by mikepier View Post

Just for the heck of it, just try the VHF antenna. Remove the joiner and UHF antenna completely. See if the same thing happens. If it does, try removing the amp completely. Don't just unplug it, bypass it, hook the antenna directly into the tv.
Your tvfool results show an amp might not be needed.

The only reason I got an amp is because I read they help out a lot in attic installs. Think that could be the reason? I can definitely take the amp out of the equation. Thx man!
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Old 12-20-2011, 10:41 AM - Thread Starter
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Originally Posted by Digital Rules View Post

Those are both excellent choices. The Blonder Tongue HLSJ should perform just as well as the Pico Macom.

Cool, thx. I pulled the trigger on them. For $8 shipped, I couldn't help it. Also order some new coax cables from Amazon as the ones I'm using I've had for years. No idea if they're involved too.
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Old 12-20-2011, 11:43 AM
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Still, try removing the amp. They can sometimes amplify several kinds of VHF interference that might make the signal drop to -0-....
What is your roof made of?
What are your exterior walls made of?
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Old 12-20-2011, 01:07 PM
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Quote:


Also, ADTech, it seems that Pico-Macom HLSJ is no longer sold. Do you know of a website where I could buy that or something similar?

P-M HLSJ devices are now branded as "TRU SPEC"
http://www.sterenshopusa.com/catalog...igh---low-band

I picked that one because, when compared to a similar Holland, offered a bit more rejection of the VHF aircraft band. I have not tested the BT HLSJ, so I don't know its cutoff frequencies.

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Old 12-20-2011, 07:54 PM
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Quote:
Originally Posted by jubei_nj View Post

BTW, when you say "off-axis" do you mean pointing it towards the sky instead of straight? I ask because I felt like my signal got better as I pointed it upwards more. My DB8 is pointed straight ahead.

The rest of my comment, horizontally or vertically did include toward the sky (vertically). The horizontally meant other than directly towards the station. Sometimes you can cancel reflections by luck.

This troubleshooting, for we mere beginners (I definitely include myself) is often more art (or luck) than science. A good spectrum analyzer, and knowledge of how to use it, shifts the curve towards science.
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Old 12-20-2011, 07:54 PM - Thread Starter
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Originally Posted by arxaw View Post

Still, try removing the amp. They can sometimes amplify several kinds of VHF interference that might make the signal drop to -0-....
What is your roof made of?
What are your exterior walls made of?

Roof is made of asphalt shingles. Walls are both plaster and Sheetrock but up there, there are no walls.
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Old 12-20-2011, 07:56 PM - Thread Starter
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Quote:
Originally Posted by gbynum View Post

The rest of my comment, horizontally or vertically did include toward the sky (vertically). The horizontally meant other than directly towards the station. Sometimes you can cancel reflections by luck.

This troubleshooting, for we mere beginners (I definitely include myself) is often more art (or luck) than science. A good spectrum analyzer, and knowledge of how to use it, shifts the curve towards science.

Oh cool. I'm trying that tonight. I did try turning it side to side and definitely picked up better signal. I just figured that I was turning it to the right compass bearing.
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Old 12-21-2011, 08:42 AM
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Attic reception is a crap shoot. Be patient and try all sorts of unorthodox aiming and you may find a sweet spot for reliable reception of all your channels of interest. Aiming off-axis (up/down, left/right), instead of directly at the towers may help. Sometimes, you also may have to physically move antennas to a different spot to find a hot reception spot.
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Old 12-22-2011, 09:43 AM
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And I don't see that it was mentioned ... after each move or angle change, give it some time ... often 30 seconds or more. Unlike analog, the digital tuners "processing, processing, processing" takes a little while.

I find that it is essential to take notes on difficult (meaning the first try was not successful) projects. I'll often draw a N S E W cross and add the NE NW SE SW. I don't worry about laying it out correctly, just to refer to as I point the antenna different ways.
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Old 01-04-2012, 11:55 AM - Thread Starter
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Thx for all the help guys, quick update....

- Pointing it more skyward definitely helps with reception quality.
- The VHF filter hasn't helped. I have the CLEARSTREAM5 going into the LINE side, the Low is termimated and the HIGH goes into the combiner.
- I tried it without the preamp but the signal on ALL channels dropped by almost 40%.

At this point, I'm considering putting the antennas outside or getting an antenna (Channel Master 4228HD?) that does both UHF and VHF and put it in the place of the DB8. That sound logical? I'd really not like to go outside if I don't absolutely need to but would it solve the multipathing?
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Old 01-04-2012, 08:23 PM
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Quote:
Originally Posted by jubei_nj View Post

...At this point, I'm considering putting the antennas outside or getting an antenna (Channel Master 4228HD?) that does both UHF and VHF and put it in the place of the DB8. That sound logical? I'd really not like to go outside if I don't absolutely need to but would it solve the multipathing?

The 4228HD will, in fact, receive high VHF at your signal strengths. But you already have a high VHF antenna. Per your TVFool, you really don't need that much antenna, but in the attic, it's impossible to predict what might work more reliably. Perhaps nothing in the spot your current setup is in.

I would first remove the preamp, which is probably not needed and may actually be amplifying nearby sources of VHF interference. If no better, I would look at installing an antenna outside. For the channels in green & yellow (compass direction 92°) on your TVFool, you shouldn't need any more antenna than an ANT751, installed outdoors.
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Old 01-04-2012, 08:26 PM - Thread Starter
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Originally Posted by arxaw View Post

The 4228HD will, in fact, receive high VHF at your signal strengths. But you already have a high VHF antenna. Per your TVFool, you really don't need that much antenna, but in the attic, it's impossible to predict what might work more reliably. Perhaps nothing in the spot your current setup is in.

I would first remove the preamp, which is probably not needed and may actually be amplifying nearby sources of VHF interference. If no better, I would look at installing an antenna outside. For the channels in green & yellow (compass direction 92°) on your TVFool, you shouldn't need any more antenna than an ANT751, installed outdoors.

Funny you mentioned that antenna. I saw a lot of multipath/attic success with that antenna earlier today and since it's so cheap, and I'm a prime member, I bought it. We'll see how that does in the attic. I'm almost to the point of re-signing with FiOS TV but I really love my current EyeTV/HDHomeRun setup a lot.
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Old 01-05-2012, 05:52 AM
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There may be interference and/or multipath issues in your attic space that will plague any antenna installed there. If so, you will need to move it outdoors. The ANT751 is small and very unobtrusive.

Initially install it without the preamp and its power supply. You shouldn't need any amplification and it may be causing some of your problems.
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Old 01-05-2012, 08:49 AM - Thread Starter
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Quote:
Originally Posted by arxaw View Post

There may be interference and/or multipath issues in your attic space that will plague any antenna installed there. If so, you will need to move it outdoors. The ANT751 is small and very unobtrusive.

Initially install it without the preamp and its power supply. You shouldn't need any amplification and it may be causing some of your problems.

Yeah that's what I'm afraid of. My hesitation for installing it outside is grounding it from direct strikes. I've read some detailed articles on the subject. Some say to ground it to a cold water pipe that you know goes underground (which I don't think I have), others say to bury a grounding pole 8 ft (kind of tough with how hard the ground will be right now in NJ), and still others say to ground it to your breaker box which present challenges based on where my breaker box is compared to where the antenna would go.
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Old 01-05-2012, 03:35 PM
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Yeah that's what I'm afraid of. My hesitation for installing it outside is grounding it from direct strikes. I've read some detailed articles on the subject. Some say to ground it to a cold water pipe that you know goes underground (which I don't think I have), others say to bury a grounding pole 8 ft (kind of tough with how hard the ground will be right now in NJ), and still others say to ground it to your breaker box which present challenges based on where my breaker box is compared to where the antenna would go.

If you ground it to something other than your main electrical ground (another ground rod or a water pipe), you still need to "bond" or connect that ground to your main electrical system ground.

The purpose of the grounded antenna is to keep static charges from building up on the antenna as wind blows across it. This only makes the antenna less attractive to lightning, it will not protect equipment in the event of a direct hit.
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Old 01-05-2012, 09:21 PM
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WNJB on RF8 is close to your location and very strong. I'm guessing it is causing adjacent channel interference to RF7. Can you check the signal levels on RF7 and RF8? Typical receivers cannot properly decode the desired channel if an adjacent channel is 10 to 15 times stronger.
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Old 01-06-2012, 08:02 AM - Thread Starter
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WNJB on RF8 is close to your location and very strong. I'm guessing it is causing adjacent channel interference to RF7. Can you check the signal levels on RF7 and RF8? Typical receivers cannot properly decode the desired channel if an adjacent channel is 10 to 15 times stronger.

I'm not sure how I could do that. Could you let me know what I have to do?

Update on the RCAANT751 antenna: Got it yesterday, installed in the place of the DB8. Without the pre-amp, signal strength again was down (same with the DB8/CLEARSTREAM5 combo). Put the pre-amp on, much better. Problem is, my UHF reception was dropped from 100% on the DB8 w/ pre-amp to about 60-70%. I haven't noticed that it makes much of a difference since the channels come in just the same. The big thing I noticed is that my channel 7 reception has improved 5-10% and so far (again, small sample size!) I haven't see the glitches I was seeing before. Worst case scenario, I can see this definitely replacing the CLEARSTREAM5 as the VHF antenna since the VHF gain far outdoes the CLEARSTREAM5 at almost half the cost. Best case scenario, even with the lower signal strength (60-70% on UHF) it performs just fine and can replace both antennas at almost 1/4 the cost. I'll keep this thread updated.

I'm also going to move it to a different part of the attic to see if I can get even better signal. The fact that pointing it skyward still improves signal tells me I'm not getting it over my neighbor's house. This would be tricky to do even outside since we have a ranch while our neighbors have 2 floors (for the most part).
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Old 01-06-2012, 08:09 AM
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60-70% signal strength is not a problem if the signal is relatively steady and consistently above the threshold needed to maintain a lock on the station. That's all you need.

If you have dropouts later, do go ahead and look for better reception hot spots in the attic. If you find one, move the antenna there. You're likely getting all sorts of bounced signals in that space.
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Old 01-06-2012, 08:16 AM - Thread Starter
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So maybe it could be that as I've read elsewhere, this antenna really does mitigate multipathing. It's probably because even tho it's not advertised as such, I've read it's very directional.
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Old 01-06-2012, 08:25 AM
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It is fairly directional.
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Old 01-06-2012, 08:37 AM
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Quote:
Originally Posted by jubei_nj View Post

I'm not sure how I could do that. Could you let me know what I have to do?

You can use your HDHomerun software and report back what the signal strengths are on RF7 and RF8.
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Old 03-11-2013, 12:09 PM - Thread Starter
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Guys,
I know it's been over a year but hopefully some of you still follow this thread.

A few months ago, I thought I had my channel 7 problems solved. Then, I started having issues with 7 WABC in the morning and night. During the day, channel 7 works pretty flawlessly. I've tried multiple antennas including the Clearstream 5 VHF antenna specifically made for this type of this. I'm currently using a Winegard 7694P on a chimney mast on the roof and like the Clearstream 5, up until about 4-5pm, the signal (without an amp) is full on my TV. At night, the signal drops off completely and channel 7 is unwatchable. I've tried taking everything out of the mix (wires, the splitter I use, etc) and everything is still messed up.

Is anyone from the NYC area having similar issues with channel 7? I should mention that channels 9, 11, 13 - all VHF channels - remain completely watchable at all times with pretty decent signal.

Thanks in advance guys!
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Old 03-11-2013, 05:26 PM
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retiredengineer in post #23 has make a good point.

When you replaced the CS5 with the ant751 in the attic you said that CH7 improved. Since the 751 probably has a more narrow horiz beamwidth than the CS5, that seems to confirm his suspicion that CH8 is causing adjacent channel interference to CH7. Notice the little red a beside CH7 in your tvfool report.

If your antennas were still in the attic, I would have suggested that you cover a large sheet of cardboard with aluminum foil and place it on the south side of the 751 to block the CH8 signal before it reaches the 751. But, outside that is a little more difficult. There are custom (expensive) filters that can attenuate the very strong CH8 signal so that it doesn't overpower the CH7 signal in the tuner.

The specs for tv tuners to reject adjacent channel interference are in ATSC A74:

http://www.atsc.org/cms/standards/a_74-2010.pdf

ATSC Recommended Practice:
Receiver Performance Guidelines
Document A/74:2010, 7 April 2010

Page 15
5.4.2 Adjacent Channel Rejection



Notice that WNJB is 33.8 dB stronger than WABC, which puts you right at the dividing line between success and failure.

The other possibility is that you have a high noise level on VHF. It usually is stronger on VHF-low than on VHF-high, and it is stronger at the CH7 end of VHF-high than on CH13. If the CH7 signal isn't 16 dB stronger than the noise level, it will suffer interference.




Noise acts like another DTV signal to cause co-channel interference. If you listen to a DTV signal with an analog signal level meter that has the audio monitor turned on, it will sound like random noise ("white noise").

I have a CH11 signal that has pixellation. Its strength is about -10 dBmV (-58.5 dBm), which is much stronger than the minimum required signal of -84 dBm for most tuners. But, the noise level for VHF-high at my location is about -20 to -25 dBmV (-68.8 to -73.8 dBm) which doesn't leave enough safety margin (must be at least 16 dB) between the signal and the noise for reliable reception.
http://www.avsforum.com/t/381623/the-official-avs-antenna-and-related-hardware-topic/14940#post_22100205

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