Choppy Audio and Video on TV without STB
bellyer
Newbie

For about a week now, a 23" Samsung LCD TV that we have in our bedroom has been pretty much unwatchable because the video and audio signals have been extremely choppy, sometimes it won't even display an image or output any sound.  For this TV we do not have a STB because the TV has a Clear QAM tuner and we really only watch network programming on it.  All other video works fine on the TV in the bedroom; DVDs play just fine without any A/V signal interruptions.  The problem has happened before, but then gone away on it's own for a few weeks, then it comes back for a few days, then goes away again.  Our TV in our living room with the STB has been fine; no issues whatsoever.

I have checked all of our connections and none of them are loose.  So, my only guess is that there is a problem with the signal that is somehow corrected by the STB on our living room TV, but since we don't have the STB in the bedroom, the signal isn't being cleared up.

I live in South Riding, VA and have had FIOS for over a year and a half and love it, but this one issue is driving me insane (although, not insane enough to go back to Comcast).

If anyone has any advice on how to fix this problem, I would greatly appreciate it.

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Re: Choppy Audio and Video on TV without STB
Keyboards
Master - Level 3

It is quite possible that the signal is too strong for the TV tuner and is causing a front end overload.  You might try attenuating the signal to the TV to see if that improves things. 

Attenuators can be ordered from SMARTHOME.COM for around $13.00 for a bag bag of mixed values.  Start with the highest and work your way down if the first one is enough to cause total signal loss.  If you need to, the attenuators can be stacked to get in between values of attenuation.

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Re: Choppy Audio and Video on TV without STB
bellyer
Newbie

Now, before I go ahead and order the attenuators, I don't suppose that there is some way to check the signal strength to see if it is too strong, is there?

Also, since this isn't a permanent problem (seems to come and go every week or so), if I install an attenuator, will it degrade the signal at times when the problem wouldn't be occurring anyway? 

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Re: Choppy Audio and Video on TV without STB
spacedebrisR
Contributor - Level 1

Yes, you can check the signal level, but it would require you to bring one of your STB's from another room into here.

What you would do is bring in any of your full size STB's and hook it up as if you were going to use it in this room. 

Once connected and you get the picture on the tv screen via the cable box...

walk up to the box and starting with it turned ON

Press  Power---->Select----->Select.   In that order

This should bring up a diagnostic screen on the tv.

Go to the line that says "inband service" and press the right arrow button

then find the line that says  SNR

This number should be between 31-37db

If it is 36db or higher, you will probably want an attenuator.

If the number is lower than 31, then the signal may not be strong enough. Both conditions, low and high will both cause the same symptoms.

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Re: Choppy Audio and Video on TV without STB
Keyboards
Master - Level 3

@spacedebris wrote:

Yes, you can check the signal level, but it would require you to bring one of your STB's from another room into here.

What you would do is bring in any of your full size STB's and hook it up as if you were going to use it in this room. 

Once connected and you get the picture on the tv screen via the cable box...

walk up to the box and starting with it turned ON

Press  Power---->Select----->Select.   In that order

This should bring up a diagnostic screen on the tv.

Go to the line that says "inband service" and press the right arrow button

then find the line that says  SNR

This number should be between 31-37db

If it is 36db or higher, you will probably want an attenuator.

(emphasis added)

If the number is lower than 31, then the signal may not be strong enough. Both conditions, low and high will both cause the same symptoms.


WRONG!!  SNR is signal to noise ratio and not the signal strength - usually specified in dBm not dB.  Even an attenuated signal can have an SNR of 36 dB.

 Scott -

My TV (a Sharp Aquos) has a menu selection under DIGITAL CHANNEL SETUP for channel strength.  If you have something similar it will give you a relative signal strength.  In my case it is a number between 0 and 100 with anything between 50 and 90 working without issue.  It should also be a steady reading - a "jumpy" reading could possibly indicate an overload condition.

Unfortunately I don't know any other way for to check strength of signal.  If the attenuators work, it means you have an excess of signal and  probably will have no issues if the signal goes down a bit since the AGC (automatic gain control) in the TV should handle that variation.

If you don't want to buy the attenuators you can use splitters as attenuators (at least as a test).  A 2 way is typically 3.5 dB, 4 way is  typically 7 dB and cascading you just add the attenuation numbers.  If using splitters, be sure to terminate all unused ports on the splitters. Keep in mind that many TIVO users have required 10 dB or more to eliminate RF overload problems.

Hope that helps.

Message Edited by Keyboards on 05-08-2009 06:52 PM
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Re: Choppy Audio and Video on TV without STB
spacedebrisR
Contributor - Level 1

Actually. I am EXACTLY RIGHT.....  Yes, it does mean signal to noise ratio.  key being SIGNAL. This is how Verizon checks and measures the signal.

When this number is high, Verizon puts in an attenuator to bring it down.

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Re: Choppy Audio and Video on TV without STB
Keyboards
Master - Level 3

@spacedebris wrote:

Actually. I am EXACTLY RIGHT.....  Yes, it does mean signal to noise ratio.  key being SIGNAL. This is how Verizon checks and measures the signal.

When this number is high, Verizon puts in an attenuator to bring it down.


Where did you get your engineering degree?  SNR is the RATIO of signal to noise NOT the signal strength - in other words it is how high above the noise floor the signal is and indicates how "clean" the signal is not how strong it is.  Signal strength is specified in dBm and amplitude in volts.  You can have a signal in the microvolts, millivolts, volts, kilovolts etc. and all can have the same SNR.  However, an RF front end certainly won't handle kilovolts (extreme overload) but will be quite happy with a few hundred microvolts.

 Please review your theory before posting erroneous information.

EDIT - BTW my understanding is that Verizon installers use a Sunrise meter which measures signal strength, band tilt, in addition to SNR and other functions (like BER and constellation) depending on the model.  Any Verizon techs want to confirm or deny? Smiley Very Happy

Message Edited by Keyboards on 05-08-2009 08:08 PM
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Re: Choppy Audio and Video on TV without STB
bellyer
Newbie

Okay, so I had a few splitters laying around the house, so before purchasing some of the attenuators, I decided to put two splitters into the line in between the wall jack and the tv itself.  Doing this had no effect on the audio and video; it was still a choppy picture and choppy audio.

I did find a signal measuring application in the TV's menu.  It does not provide any sort of numerical signal strength measurement.  It is a series of bars, like what you would find on a cell phone for signal strength.  With and without the splitters attached, the signal was constantly bouncing around.  It would be 1 or 2 bars one second, then it would be full strength (7 or 8 bars), then it would drop down to like 4 or 5, then down to 1 or 2 again, and so on and so forth.

I have read that amplifiers would have no effect on the FIOS signal and would in fact hurt the signal on all the tvs in the house.  As I said, our TV in the living room that utilizes a STB has no problems at all.  It is just the signal coming into the TV in the bedroom.

If anyone has any ideas other than attenuators that might help stop choppy A/V and regulate the incoming signal somehow, I am all ears.  Thanks. 

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Re: Choppy Audio and Video on TV without STB
Tinker
Newbie

Just a shot in the dark here.  Is there a barrel at thea wall plate that could be bad?

I ran into a similar problem previously, where the barrel was bad.  My sunrise meter was giving me all sorts of readings. I replaced spliters, cable and fittings.  Finally, I had to trace the line all the way through the attic to find a random barrel that was bad.  I assume that your cable is Quad shielded RG6, and was previously installed by a Verizon technician which tested the line assuring it will perform properly.  Hope this doesn't add to your frustration.   But it seems to be the little things that give us the "Ahah" when we check them out. 

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Re: Choppy Audio and Video on TV without STB
Keyboards
Master - Level 3

@bellyer wrote:

Okay, so I had a few splitters laying around the house, so before purchasing some of the attenuators, I decided to put two splitters into the line in between the wall jack and the tv itself.  Doing this had no effect on the audio and video; it was still a choppy picture and choppy audio.

I did find a signal measuring application in the TV's menu.  It does not provide any sort of numerical signal strength measurement.  It is a series of bars, like what you would find on a cell phone for signal strength.  With and without the splitters attached, the signal was constantly bouncing around.  It would be 1 or 2 bars one second, then it would be full strength (7 or 8 bars), then it would drop down to like 4 or 5, then down to 1 or 2 again, and so on and so forth.

I have read that amplifiers would have no effect on the FIOS signal and would in fact hurt the signal on all the tvs in the house.  As I said, our TV in the living room that utilizes a STB has no problems at all.  It is just the signal coming into the TV in the bedroom.

If anyone has any ideas other than attenuators that might help stop choppy A/V and regulate the incoming signal somehow, I am all ears.  Thanks. 


The jumping of the bars could still be too strong a signal issue as the AGC in the TV gets driven nuts.  What was the total attenuation you put in the line (just add the numbers of the 2 splitters - 3.5 dB plus 3.5 dB would be 7 dB, etc.)?  The fact that the levels indicated didn't change with the attenuation is also indicative of still too much signal.  It could also be a bad barrel connector, but I would have expected the absolute level (number of bars) to be different since the signal was modified (attenuated) while the barrel was a constant.

As for amplifiers, they will work for lines that don't have a STB.  If your TV is a home run to the ingress splitter then an amplifier could be used, but it is rare that the ONT doesn't supply a strong enough signal.  In fact, many amplifiers would overload on the FiOS signal as it temds to be that strong.

Is it possible to run a temporary cable from either the splitter feeding the TV or from the line that runs the STB just to see if that clears it up.  Other than that, I'm stumped Smiley Sad

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