Broadcast TV signal strength measurement #2

Thread Starter

hap1484

Joined Feb 20, 2022
6
I have a problem receiving one family of channels in the Dallas area (NBC 5.1 over-the-air OTA). This is a new occurrence. Two years ago, I installed a very good Channel Master OTA Antenna (CM-4228HD-80 mile reception), Channel Master Adjustable Gain Pre-amp (17-30 db) and an amplified (4db) 8 port signal distribution box which has five TV connections. All channel towers are about 43 miles away and for two years the reception "on all receivable channels" has been perfect including NBC 5.1! Then on the night of the Superbowl NBC 5.1 was all pixelated. The channel would go completely off then came back on but pixelated. What a disappointment. I have an OTA channel strength meter in my Tivo Edge for Antenna and it shows a current channel strength of "46" (yellow). Tivo uses their own custom scale which is not dBm but seems to be calibrated (1-255) with 70 (green) being an acceptable signal strength. This at first was very confusing because Channel 5.1 should have a dBm rating of -55.74 dBm on Channel Frequency 24 on 530Mhz but Tivo doesn't measure this way. That aside, Tivo in their own backward way is useful for rudimentary channel strength evaluation. A reading of "46 (yellow)" is on the border of pixelation. Interestingly enough ALL OTHER CHANNELS come in perfectly at a rating of around "70 (green)". When I installed the system in 2020, NBC 5.1 was "70 (Green)" on the scale and came in perfectly with all the rest. Now it is "46 (Yellow)"? So, what made NBC Channel 5.1 go from "70" to "46"? I called and talked to an NBC Engineer. He said that NBC was having no transmission difficulties and received no OTA Superbowl complaints. He further said, "The difficulties must lay somewhere in my home system"! OK but what? Nothing has changed! A fresh channel scan does not fix the problem. Rats have not eaten the coax! The coax runs from the distribution amplifier are not excessive (about 50 feet for the longest run) and have not changed. I considered "interference from cell phones". G5 cell phone towers are being installed daily but if this was the problem why wouldn't the interference show up on multiple channels? Could cell phone interference be messing JUST with Frequency 24 (and not the others)? This is an engineering question I'll throw out to everyone? If this is the case all OTA customers are in for a rude awakening. Cell phone companies don't seem to give a flip about OTA TV reception. Here's a case in point. Very recently Verizon and AT+T 5G installations around DFW Airport were interfering with on board aircraft altimeters. Pilot unions were refusing to fly unless some changes were made. There was a resolution but I'm not sure what? Sorry for the long-winded post, but this could become a serious problem for all OTA customers. My analysis of the problem is one of two things. Either NBC has reduced OTA channel transmission which they deny or 5G Cell phones are interfering with Frequency 24! Any opinions?

Moderator edit: New thread created from old thread.
 

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Ya’akov

Joined Jan 27, 2019
6,858
Welcome to AAC.

I would confirm proper operation of your preamp and DA. Although it seems that only one channel is being affected, the instrument you are using to test that (TiVO) is pretty blunt.

I am assuming you have made a visual inspection of the antenna and nothing seems amiss there. The antenna is designed to be broadband as so faults can affect certain frequency ranges more than others. I don’t know if the other channels you are receiving well are close in frequency to the poorly received one, but always check the input, the connections, and the active electronics whenever you have a problem like this.

By the way, I couldn’t find any FCC filings by KXAS for transmitter modifications since they retuned to the new frequency in 2018, so it doesn’t seem that they have changed.

As for the 5G, it would be unlikely that 5G sites would interfere, but doesn’t seem entirely impossible if you were very close and they were using 700MHz. I would be surprised by it being the problem, though.
 

Audioguru again

Joined Oct 21, 2019
5,427
My TV signal strengths are perfect because I have cable TV who is also my internet provider.
I can "rewind and play" channels that I am not even recording.
 

Thread Starter

hap1484

Joined Feb 20, 2022
6
Yaakov, thank you for your input. This is an extremely difficult problem to solve but I am confident that I have the right people listening and commenting. I don't think this is an NBC transmission problem. An NBC engineer thinks that one of my two amplifiers (pre-amp or distribution) has failed just on the NBC Frequencies. Channel Master Engineering thinks this is highly unlikely, but they did say that have heard a lot of complaints about cell phone interference. How their customers have determined their reception problems are due to cell phone interference is beyond me. Maybe they are AAC Members? ;)Because of this I have ordered a Channel Master Cell Phone Filter. I'll post after it is installed to see if it made a difference. If Verizon and AT+T are not too concerned about crashing a commercial airliner, they sure don't care about my TV reception. Here's the CNN Business Article on the subject: The 5G-airlines crisis was mostly averted. Here's what happened - and what we still don't know - CNN In all fairness, I have yet to determine that cell phone interference is the problem? Possibly Gremlins?
 

Ya’akov

Joined Jan 27, 2019
6,858
Yaakov, thank you for your input. This is an extremely difficult problem to solve but I am confident that I have the right people listening and commenting. I don't think this is an NBC transmission problem. An NBC engineer thinks that one of my two amplifiers (pre-amp or distribution) has failed just on the NBC Frequencies. Channel Master Engineering thinks this is highly unlikely, but they did say that have heard a lot of complaints about cell phone interference. How their customers have determined their reception problems are due to cell phone interference is beyond me. Maybe they are AAC Members? ;)Because of this I have ordered a Channel Master Cell Phone Filter. I'll post after it is installed to see if it made a difference. If Verizon and AT+T are not too concerned about crashing a commercial airliner, they sure don't care about my TV reception. Here's the CNN Business Article on the subject: The 5G-airlines crisis was mostly averted. Here's what happened - and what we still don't know - CNN In all fairness, I have yet to determine that cell phone interference is the problem? Possibly Gremlins?
I would still encourage you to confirm proper operation of the antenna and amplifiers. Even if it seems unlikely, it is best practice in solving a problem like this to confirm the inputs and outputs are otherwise as expected. I have personally found on many occasions that omitting this step lead to a long, frustrating process of discovering it would have identified the issue at the outset.
 

Externet

Joined Nov 29, 2005
1,960
Television reception is the worst diarrhea of technical tasks.
Your superduper Channelmaster and any other now marketing-rated in 'miles' are prone to be replaced by a coat hanger yielding better reception. It is all empirical.
Sick of buying and trying supposedly well designed brand-name expensive preamplified antennas, settled to make a non-calculated 1 metre diameter horizontal circular loop tossed in my attic space and am not going back to anything else. The pre-amplifiers and power injectors and signal splitters and baluns went to the junk box. The wire loop inside a protective 'hula hoop' piece of pex pipe won.

Yes, sure... :oops: a piece of aluminium foil sandwiched in plastic worth 5 cents is now the cat's meow ! :

1645412723285.png
 

ricd

Joined Feb 20, 2022
7
My antenna has a built-in LTE filter and amplifier. A friend who was having pixelation issues installed an LTE filter fixed the issue, but he was having issues with all channels above 19.
He said it was only affecting one channel. AntennaWeb shows all towers in the same location. It's just puzzling, to me. With antenna amplifiers, the noise floors and signal to noise ratios play into the mix. My first distribution amplifier was an Antennas Direct CDA4 with a noise floor of 2.6db and gain of 7.5db. I replaced it with a Channel Master CM 3414 with a noise floor of less than 2db gain of 8db. That 1db difference yielded 30 more channels, from 55 channels at the closest TV, to 85 channels at the closest TV to the distribution amplifier. Small changes can make big differences in how a tuner picks up a solid signal.
 

Ya’akov

Joined Jan 27, 2019
6,858
My antenna has a built-in LTE filter and amplifier. A friend who was having pixelation issues installed an LTE filter fixed the issue, but he was having issues with all channels above 19.
It could be mobile phone transmissions interfering. Since he already has the filter ordered, we'll know one way of another when he installs it.
 

Ya’akov

Joined Jan 27, 2019
6,858
He said it was only affecting one channel. AntennaWeb shows all towers in the same location. It's just puzzling, to me. With antenna amplifiers, the noise floors and signal to noise ratios play into the mix. My first distribution amplifier was an Antennas Direct CDA4 with a noise floor of 2.6db and gain of 7.5db. I replaced it with a Channel Master CM 3414 with a noise floor of less than 2db gain of 8db. That 1db difference yielded 30 more channels, from 55 channels at the closest TV, to 85 channels at the closest TV to the distribution amplifier. Small changes can make big differences in how a tuner picks up a solid signal.
Well, the manufacturer's claims about performance don't necessarily match the product. Channel Master has a very good reputation and it is likely they are close to their published spec. I don't know the other company, so the difference could be much larger than it looks on paper.
 

drjohsmith

Joined Dec 13, 2021
549
Well, the manufacturer's claims about performance don't necessarily match the product. Channel Master has a very good reputation and it is likely they are close to their published spec. I don't know the other company, so the difference could be much larger than it looks on paper.
A few thoughts,
OK Im in the UK, which has a different , but similar digital TV system,
I see in your orriginal post comments on signal strength

Bit error rate ( BER ) is the magic number your looking for,
before and after CRC should be shown some where,
this normally has a bar, red, yellow green, green is good.

The program guide information is sent one per multiplex,
each multiplex has multiple channels on it,

So as you have multiple channels with problems , then its likely that one multiplex is having a high BER

Check the receiver , see if the BER is high,
if it is , then there should be a single strength indicator as well,
compare the BER and the signal strength across different multiplexes

That will give indication if its your end or at the transmitter, and what to do


I had here, case of to much signal strength due to the change of frequencies for a mux
ended up putting in an attenuator before the splitter to fix that !

I have also had a amplifier go "down" , in that its frequency response after a few years was down
multiplexes at the extremes of the range, had lower power than it did originally,
in that case a new amplifier helped,
 
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Thread Starter

hap1484

Joined Feb 20, 2022
6
AGAIN, I would like to thank all that have responded so far. All suggestions are read and considered (except the one to go back to "cable") :) I want to avoid the cost of cable because I watch little broadcast TV. Advertising is also up 25%! I record the ABC Evening Advertisements (billed as ABC Evening News) on my Tivo Edge for Antenna then I fast forward through the ads. As a side comment, the Tivo Edge for Antenna is a piece of junk. The "skip button" does not work so I have to pause then fast forward manually with the right arrow button. Sometimes when I turn on the Tivo the screen blinks for five minutes before it settles down.
Tivo won't play a Netflix Movie until the box is restarted. Tivo has already replaced the box once but the new one does exactly the same thing! Does anyone have one of these devices that works "fully"? Back to the antenna problem.....as I mentioned before I'll install the LTE Filter before the pre-amp when it arrives from Channel Master. I've also ordered a Signal Meter Tester to get more precise signal strength measurements. This will not fix the problem, but I can get more accurate readings for future discussions.
 

drjohsmith

Joined Dec 13, 2021
549
AGAIN, I would like to thank all that have responded so far. All suggestions are read and considered (except the one to go back to "cable") :) I want to avoid the cost of cable because I watch little broadcast TV. Advertising is also up 25%! I record the ABC Evening Advertisements (billed as ABC Evening News) on my Tivo Edge for Antenna then I fast forward through the ads. As a side comment, the Tivo Edge for Antenna is a piece of junk. The "skip button" does not work so I have to pause then fast forward manually with the right arrow button. Sometimes when I turn on the Tivo the screen blinks for five minutes before it settles down.
Tivo won't play a Netflix Movie until the box is restarted. Tivo has already replaced the box once but the new one does exactly the same thing! Does anyone have one of these devices that works "fully"? Back to the antenna problem.....as I mentioned before I'll install the LTE Filter before the pre-amp when it arrives from Channel Master. I've also ordered a Signal Meter Tester to get more precise signal strength measurements. This will not fix the problem, but I can get more accurate readings for future discussions.
signal strength matters less than BER,
 

Audioguru again

Joined Oct 21, 2019
5,427
All the ads on TV are for my amusement. For each burst of ads I laugh when the same ad appears next after it finished playing.
The most frequent ad is Russel Olivah Jewelery and now I think he gives mortgages because he has made so much money ripping off people who buy his used jewelry. He says Olivah instead of saying Oliver because of his English accent.

I also record a lot of shows on cable TV then I can also skip the ads when playing back.
 

ricd

Joined Feb 20, 2022
7
Last year during the Super Bowl pregame show, Cox cable had an outage and was not fixed until the following day. I was watching the game on my side patio which is covered and has no walls with a Klipsch soundbar and subwoofer. Neighbors came over and asked why I still had cable. I showed them my TV antenna above the roof, which is white and barely visible from the street and invited them over to watch the game. I opened up the garage, where I have another TV with a TCL soundbar. There was plenty of room for social distancing the families. Cable TV is not always reliable.

My TV signal strengths are perfect because I have cable TV who is also my internet provider.
I can "rewind and play" channels that I am not even recording.
 

ricd

Joined Feb 20, 2022
7
If you live in an HOA there can be certain restrictions on antenna height and physical size of the antenna. The FCC has a ruling that prevents HOAsfrom restricting homeowners on placing an antenna to get the best signal. The attached photo is the back of the antenna from the front of the house. We have a very long driveway on a downhill slope, so the antenna is almost undetectable from the street


Almost nobody in my city has an outdoors TV antenna so maybe they are illegal. A few people have small satellite dishes.
 

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