sowny.net | The Southern Ontario/WNY Radio-TV Forum


You are not logged in. Would you like to login or register?

October 24, 2022 1:11 pm  #1


Technical Question: Signal Strength Vs. Signal Quality

I admit to being a Luddite when it comes to all things engineering, so I'm hoping one of the many experts in that field who gather here can explain what happened to me last night. I was trying to record some shows over-the-air from WUTV in Buffalo. But try as I might with a 40' high outdoor antenna with a rotor and a signal booster, I simply could not get a signal. 

So I checked the technical specs on my DVR. It said that signal strength was close to 80 or 90 (out of 100.) But signal quality was at 0 or 1, and as a result, all I saw was a black screen. My question: how is this possible? How can a signal be almost 100% and very strong, yet still produce no picture in my location? I simply don't get it. If the signal is that strong, shouldn't a decent picture follow? 

The weather, as you know, has been great the past few days, with no rain or real humidity and there's nothing blocking my antenna. 

Instead, even with moving the rotor around outside, the best I was able to get signal quality-wise was a 5 (out of 100.) And thus my hope to see my shows faded to black, just like the screen I was watching. 

I can't figure out how that can be. If a station is coming in strongly, shouldn't it come in in all ways? I think I've asked this before, but I'm still not quite sure I understand. If someone can explain this in non-technical English, I'd love to learn what was going on. (Channel 29, by the way, is back on Monday and coming in perfectly again.)

 

October 24, 2022 1:40 pm  #2


Re: Technical Question: Signal Strength Vs. Signal Quality

It could be any number of things, but here's my best guess: because of the good weather, there was tropospheric ducting going on last night that was bringing in some distant signals (WHOT 101.1 Youngstown OH was making it in to Rochester, for instance.)

I'd bet a couple of Toonies and a Coffee Crisp that in addition to WUTV's signal, there was also something else on the same RF channel (32) that was reaching your antenna. So it was getting lots of RF ("signal strength") but couldn't clearly decode either the bitstream from WUTV or the interfering station, hence the low "signal quality." 

The tropospheric ducting subsided this morning and so you're getting WUTV again. 

Other circumstances that can cause high signal strength but low signal quality could be multipath reflections from tall buildings or airplanes, or even problems with the encoder at the transmission end of things. 

 

October 24, 2022 1:41 pm  #3


Re: Technical Question: Signal Strength Vs. Signal Quality

Last night all the Buffalo stations were exceptionally strong and many from Rochester were coming in in North Mississauga.Without knowing where you are located I could only speculate.Perhaps its overload of the preamp or tuner causing the issue?This distorts the signal so  quality shows 0.My Tablo/PVR used to the same thing until split signal before PVR reducing signal 4.5 db.

 

October 24, 2022 1:43 pm  #4


Re: Technical Question: Signal Strength Vs. Signal Quality

There was tropo reception of far away signals last night due to weather conditions. I picked up WPNT Pittsburgh last night here in WNY. When you have these weather conditions the far away signals can interfere with the fragile ATSC 1.0 signals. I had trouble receiving the Toronto stations which usually I have no trouble with. With ATSC 1.0 any disruption or multipath and the signal will not decode. There was no technical problems with WUTV.

Last edited by canam2021 (October 24, 2022 1:52 pm)

 

October 24, 2022 2:03 pm  #5


Re: Technical Question: Signal Strength Vs. Signal Quality

I suspect the conditions had something to do with it, because nothing else was different and it's fine now. But you'd think when we have such good weather, it would help not hurt reception. As usual, HD is a lot different than analogue, and sometimes, what you see is what you get.

Or in my case, what you don't see. 

     Thread Starter
 

October 24, 2022 2:07 pm  #6


Re: Technical Question: Signal Strength Vs. Signal Quality

fybush wrote:

It could be any number of things, but here's my best guess: because of the good weather, there was tropospheric ducting going on last night that was bringing in some distant signals (WHOT 101.1 Youngstown OH was making it in to Rochester, for instance.)

I'd bet a couple of Toonies and a Coffee Crisp that in addition to WUTV's signal, there was also something else on the same RF channel (32) that was reaching your antenna. So it was getting lots of RF ("signal strength") but couldn't clearly decode either the bitstream from WUTV or the interfering station, hence the low "signal quality." 

The tropospheric ducting subsided this morning and so you're getting WUTV again. 

Other circumstances that can cause high signal strength but low signal quality could be multipath reflections from tall buildings or airplanes, or even problems with the encoder at the transmission end of things. 

Certainly sounds plausible. Is there any way to predict when these interference conditions are happening? I can always make other recording arrangements if I know about them in advance.

     Thread Starter
 

October 24, 2022 2:59 pm  #7


Re: Technical Question: Signal Strength Vs. Signal Quality

Anytime my antenna picks up CTV2 in Barrie, I know there is bad tropo happening!
 

 

October 24, 2022 4:07 pm  #8


Re: Technical Question: Signal Strength Vs. Signal Quality

RadioActive wrote:

fybush wrote:

It could be any number of things, but here's my best guess: because of the good weather, there was tropospheric ducting going on last night that was bringing in some distant signals (WHOT 101.1 Youngstown OH was making it in to Rochester, for instance.)

I'd bet a couple of Toonies and a Coffee Crisp that in addition to WUTV's signal, there was also something else on the same RF channel (32) that was reaching your antenna. So it was getting lots of RF ("signal strength") but couldn't clearly decode either the bitstream from WUTV or the interfering station, hence the low "signal quality." 

The tropospheric ducting subsided this morning and so you're getting WUTV again. 

Other circumstances that can cause high signal strength but low signal quality could be multipath reflections from tall buildings or airplanes, or even problems with the encoder at the transmission end of things. 

Certainly sounds plausible. Is there any way to predict when these interference conditions are happening? I can always make other recording arrangements if I know about them in advance.

Check out William Hepburn's site:
Tropospheric Ducting Forecast for VHF & UHF Radio & TV (dxinfocentre.com)

 

 

October 24, 2022 4:17 pm  #9


Re: Technical Question: Signal Strength Vs. Signal Quality

Thanks. I'll bookmark it. Could prove useful if only to explain why it's not coming in the next time. 

     Thread Starter
 

October 25, 2022 10:00 am  #10


Re: Technical Question: Signal Strength Vs. Signal Quality

pinto wrote:

Anytime my antenna picks up CTV2 in Barrie, I know there is bad tropo happening!
 

On Channel 3?  Where are you located. 

 

October 25, 2022 11:53 am  #11


Re: Technical Question: Signal Strength Vs. Signal Quality

markow202 wrote:

pinto wrote:

Anytime my antenna picks up CTV2 in Barrie, I know there is bad tropo happening!
 

On Channel 3?  Where are you located. 

My mistake, meant Hamilton 35.1.  only get it during tropo in Whitby
 

 

October 26, 2022 7:55 am  #12


Re: Technical Question: Signal Strength Vs. Signal Quality

canam2021 wrote:

There was tropo reception of far away signals last night due to weather conditions. I picked up WPNT Pittsburgh last night here in WNY. When you have these weather conditions the far away signals can interfere with the fragile ATSC 1.0 signals. I had trouble receiving the Toronto stations which usually I have no trouble with. With ATSC 1.0 any disruption or multipath and the signal will not decode. There was no technical problems with WUTV.

I have often wondered what kind of reception  OTA Western New York viewers receive from the Toronto stations. Global TVO have fairly strong signals. CFTO  and CITY not so much.

 

October 30, 2022 9:27 pm  #13


Re: Technical Question: Signal Strength Vs. Signal Quality

OK, here's another one that's simply inexplicable to me. On Sunday night, I was getting a strong signal from WUTV, but no signal quality. Which meant a black screen. That's similar to what happened before.

But this isn't. In an effort to figure out if my antenna was off directionally, I decided to completely reorient it. 

In case you've never had a rotor, that simply means turning it all the way north one way, then turning it back around to the south, and up north the other way. The final step is aiming it as best you can towards Buffalo, in this case Grand Island where WUTV's transmitter is located. 

So far, so good. But when I swung the thing full north - about where Barrie's CTV2 should be, WUTV suddenly came in perfectly with possibly the best signal it's been since it was forced off the air due to transmitter problems last week. So let me get this straight - I aim my antenna as far away from the originating signal as possible and that's when it comes in the best. 

I've never claimed to be an expert on technical issues but this makes absolutely no sense to me at all. 

     Thread Starter
 

October 30, 2022 10:37 pm  #14


Re: Technical Question: Signal Strength Vs. Signal Quality

I'm not sure exactly what your antenna setup is or where you're viewing from, but it's entirely possible that you were getting a reflection of the WUTV signal from a tall building north of you that might be stronger that the signal reaching you directly, if that direct signal is blocked by other city buildings. 

(Also worth noting there was massive tropo ducting again this morning. Headed from Rochester to Buffalo, I was hearing most of the Ottawa FM dial along the Thruway. It subsided by midday.) 

 

October 30, 2022 11:13 pm  #15


Re: Technical Question: Signal Strength Vs. Signal Quality

I noticed that tropo Sunday morning when Channel 67, WBBZ from Springville, N.Y., came in very powerfully. It's a rare catch up here as a LPTV and it was as good as I've ever seen it. It was gone by noon. Your theory about WUTV makes sense, I suppose, but it certainly is a weird way to have to pull in a Buffalo signal - from the wrong end!

I guess I'll have to keep it in mind for the next time 29 doesn't shine!

Most of the signals on Sunday night are fickle - there one minute, gone the next, with the exception of WGRZ, which is always strong here in Northern North York. It's been an interesting few weeks with stuff phasing in and out. Too often, sadly, out!

     Thread Starter