Terrestrial picture randomly breaking up - reboot receiver fixes it

[adm]

Thanks ccs, will try that, difficultly I have is that I cannot replicate or predict when I get them; although do seem to happen after recording programs on a given channel.
Out of interest, as mentioned previously I do seem to get these on given Channels e.g. ITV4, BBC, is this indicative of such a signal/attenuator issue - where some channels frequency/signal seem ok and only affected on others?

In the UK you will typically receive your terrestrial broadcasts on 6 Multiplers (MUX). These MUXs are transmitted at different frequencies and maybe at different transmitted powers levels. You can check the transmitted powers for each MUX by going to the web page for the transmitter. Local service MUXs seem to be transmitted at relatively low power compared to the main channel MUXs.

Assuming all the MUXs signals arrive at you house with the same power levels (unlikely) the response of your aerial and even the quality of down-lead will result in some MUX signals arriving at you box with signal levels higher than the signal levels for other MUXs.

If, and it's still speculation, the problem is too high a signal level some MUXs may be over-loading the from end of the box more than others. TV channels carried by one MUX may be OK whereas the TV channels carried by another MUX may be causing the front end over-load. If you go to the web page for your transmitter you can see which TV channels are carried on each MUX. Do you only get the breakup on on the channels carried by the one MUX?

 

[Stuey2017a]

.... Do you only get the breakup on on the channels carried by the one MUX?

Thanks again for the explanation adm, as for getting breakup, I do seem to exhibit it more on MUX "D3&4" and "BBC A", although these are the main channels which I record off and assume if I frequently recorded on other MUX's then I'd see similar across the board..

 

[adm]

I've got an unexplained terrestrial aerial problem at the moment.

Brand new aerial and cabling - signal/picture is absolutely fine on all mux's, until it rains.

Then just one mux completely fails - zero signal. All the others are 100% fine.

There are trees which could be an issue (they are due to be trimmed), but I can't see why just one mux should totally fail.

Which transmitter? Which MUX? What aerial? What cable?
My first guess would be that the dodgy MUX is at the higher end of the transmitter frequencies.
Are you splitting the signal and if so how many ways and has the splinter got a spare output?

 

[goRt]

If it helps, had an email off WoS this morning pointing me to this (which I have already purchased!):

http://www.ebay.co.uk/itm/Plug-In-C...d=390993822038&_trksid=p2385738.c100677.m4598

Ordered and dispatched already.

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[ccs]

Which transmitter? Which MUX? What aerial? What cable?
My first guess would be that the dodgy MUX is at the higher end of the transmitter frequencies.
Are you splitting the signal and if so how many ways and has the splinter got a spare output?

Belmont, it's the highest frequency, 785.8MHz, 100,000W, C60-. Strongest mux is 150,000W.

Splitter is powered, variable gain, new - swapping around or removing altogether makes no difference.

Wideband aerial, WF100 cable.

Problem shows up on a tv directly connected to the aerial.

 

[ccs]

It's raining , C60 has no signal, but local channel C27 (522MHz), just 5,000W, has a signal strength of 100%.

 

[ccs]

Ok, I know I've gone off topic, but it was really to highlight that terrestrial signal quality on different channels can vary wildly.

Both my TV's are 10+ years old, and show zero signal strength at the moment on C60.

I've just tried a tv with a T2 tuner, and it's reporting signal strength approaching 50%, so it looks like the tuners in my sony TV's are not particulary good at the high frequency range.

 

[Stuey2017a]

Attentuator arrived and is in-situ, have adjusted it (its a variable attentuator) to about half way, the effect has been most channels SNR remain at 99% (as before) but some channels on the same MUX have dropped from 99% SNR to 84% and 87%. If I turn the attenuator down further some MUX channels break up constantly (others remain fine).

The Channels I've noticed the recording/breaking up picture on remain at 99% SNR - as I say can't turn the attenuator down any further as other channels break up.
I will leave it run over the next couple of days to see if its making any difference...

 

[goRt]

Attentuator arrived and is in-situ, have adjusted it (its a variable attentuator) to about half way, the effect has been most channels SNR remain at 99% (as before) but some channels on the same MUX have dropped from 99% SNR to 84% and 87%. If I turn the attenuator down further some MUX channels break up constantly (others remain fine).

The Channels I've noticed the recording/breaking up picture on remain at 99% SNR - as I say can't turn the attenuator down any further as other channels break up.
I will leave it run over the next couple of days to see if its making any difference...

Mine also arrived today (great service), all channels on tuner a breaking up, inserted the attenuator and turned down until picture recovered at 84db, been running that way for an hour.
I am currently recording 2 hd channels on the same bouquet on the same tuner (a) just because I can

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[adm]

Attentuator arrived and is in-situ, have adjusted it (its a variable attentuator) to about half way, the effect has been most channels SNR remain at 99% (as before) but some channels on the same MUX have dropped from 99% SNR to 84% and 87%. If I turn the attenuator down further some MUX channels break up constantly (others remain fine).

The Channels I've noticed the recording/breaking up picture on remain at 99% SNR - as I say can't turn the attenuator down any further as other channels break up.
I will leave it run over the next couple of days to see if its making any difference...

Repeat post as my original seems to have vapourised

SNR = Signal to Noise Ratio and not necessarily an indication of input signal level.

I suggest that it may be better to adjust the attenuator so the channel with the 84% just gets to 99%

If you have purchased a variable 20db attenuator you may be reducing the signal level too far

6db reduces the signal by x2
10db reduces the signal by x3
20db reduces the signal by x10

You may need to only reduce the signal by less than x2 - so closer to the minimum setting rather than half way or maximum

 

[Stuey2017a]

Thanks adm, I have upped the attenuator so 84% now becomes 99%, which is what it was before the attentuator was inserted (as mentioned in my first post, all channels report SNR at 99%).

On OpenATV, what is a better metric of input signal level (as apposed to SNR)?

 

[ccs]

Hopefully, you have now reached a SNR of 99% but with a reduced signal strength.

 

[adm]

Hopefully, you have now reached a SNR of 99% but with a reduced signal strength.

Yes, a high Signal to Noise Ratio (SNR) is still being achieved but possibly now with a x2 or x3 lower input level which no longer causes a front end overload.

 

[goRt]

So without the attenuator I have an snr of 71db and an agc of 87-88.
Adjusting the attenuator produces a stable picture (all this relates to tuner a) where by agc drops to 84-86, and remains stable for a period of time (5mins - 8+ hours) but it is inconsistent.
I can get the failure to be very fast by reducing the attenuation or increasing - the sent drops to 0 from 70 with just a touch, at that point tuner b has no picture.

So something's not right here, either the drivers or a hardware issue.
Tuner b or the TV function correctly (unless snr drops through the floor)

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[ccs]

So without the attenuator I have an snr of 71db and an agc of 87-88.
Adjusting the attenuator produces a stable picture (all this relates to tuner a) where by agc drops to 84-86, and remains stable for a period of time (5mins - 8+ hours) but it is inconsistent.
I can get the failure to be very fast by reducing the attenuation or increasing - the sent drops to 0 from 70 with just a touch, at that point tuner b has no picture.

So something's not right here, either the drivers or a hardware issue.
Tuner b or the TV function correctly (unless snr drops through the floor)

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Should the bit I've highlighted refer to tuner a ??

In theory, changing the attenuator should move from too much signal to too little signal.
Isn't that what you're describing?

 

[goRt]

Should the bit I've highlighted refer to tuner a ??

In theory, changing the attenuator should move from too much signal to too little signal.
Isn't that what you're describing?

Well at that point both tuners lose signal (not tested the TV)

Yes the signal is dropping below some minimum requirement. But 'full' signal was causing the original issue.

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[adm]

. But 'full' signal was causing the original issue.

Or maybe not - that was a suggestion by WOS that had some merit but your testing with an attenuator suggests that it doesn't fully cure the problem.

 

[ccs]

Have you tried 5.0.028? There are some driver fixes.

 

[Stuey2017a]

From my perspective, the attenuator made a very slight difference but like goRt the issue still remains .. any other suggestions on what to try next would be appreciated ...

 

[goRt]

Have you tried 5.0.028? There are some driver fixes.

All my comments related to .028, which I've now reverted from as to gui had a number of fails.
I thought (from reading here) that the driver updates related to dvb-s crosstalk/interference which I did notice an improvement in.

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