Persistent Pixelation on Playback

[prpr]

For completeness, I found the Televes catalogue listings:

and mine is one of these:
https://www.triax.com/product/tlp-048-lte700-filter/

 

[Last.To.Know]

BTW, your table cribbed from the WebIf doesn't work properly as it includes links to your local network IP 10.0.0.14:

It works perfectly on my network...

It was just for the signal strength and quality values.

I suppose I could have dragged it into SeaMonkey to delete the last 2 columns.

 

[Rodders53]

I have trouble with Ch48 from Mendip (and 47 from Wenvoe) and, elsewhere, 48 from Waltham is noticeably worse than the rest. I wonder why.

Waltham doesn't broadcast on frequency ch48.
AFAIK adjacent channel DTT is not the issue it was with analogue either.
5G 700 MHz filters will have insertion losses and lose some not entirely insignificant amount (up to 3dB?) at ch48 probably.
Not that all of us have (or need) such filtering (yet).

Toolstation seem to have stopped carrying the Proception PROMHD12M which is a shame. The 14 is still available (for more money of course).

There are three of those masthead amps ins stock at CPC Farnell if you want some https://cpc.farnell.com/proception/promhd12m/mast-head-amp-uhf-2-way-10db/dp/AP01833
They are, of course, wideband and will be being replaced by Blake/Proception with 21-48 pre filtered versions I suspect (in due course, if there's a demand).

I have multiple distribution amps here sitting in the garage that I can bring into use if required, my aerial is in the loft near a 13A twin socket. Which reminds me that I must be -8dB in the lounge as the aerial splits to feed the kitchen TV in the loft.
I'm unlikely to ever watch/record SD COM6/Arq B programme services... and the TV decodes fine with the existing arrangement... as does the HDR-Fox-T2. From a brief glance, at the channel tuned to. At least until SDT goes on reserve antenna for some routine work/mast painting, perhaps.

 

[Last.To.Know]

Just to underline the point, the figures shown there are historical not current. They were stored on last retune. There needs to be a health warning in large letters added to that WebIF page.

Is there any way to grab the date of the last retune and display that prominently?

 

[MymsMan]

Is there any way to grab the date of the last retune and display that prominently?

Only if the humax stores the date in an accessible place, quite unlikely I think
It would be more useful if someone could work out how to access the live signal strength/quality data

 

[Black Hole]

It would be more useful if someone could work out how to access the live signal strength/quality data

That's only going to be available (if at all) for the currently tuned mux, but could be used to update the stored figure (along with a timestamp) I suppose.

 

[Owen Smith]

I'm glad I bought my own filter with proper F connectors though, but I don't know if there's much 700-800 stuff here yet - certainly no 5G service on my dog'n...

Yes but a filter from 700MHz up will attenuate at 800MHz more strongly than the old one. These filters don't have cliff edge vertical roll offs, even if we'd like them to.

 

[Owen Smith]

Not that all of us have (or need) such filtering (yet).

I don't have any near Cambridge and have no problems so far. Receiving Sandy Heath, plus Maddingley for the local mux.

 

[prpr]

Waltham doesn't broadcast on frequency ch48.

I must've confused myself somewhere down the line about channels.

AFAIK adjacent channel DTT is not the issue it was with analogue either.

Clearly not as they are all mostly butt-jointed up against each other. Just like the DSAT stuff on the analyser.

5G 700 MHz filters will have insertion losses and lose some not entirely insignificant amount (up to 3dB?) at ch48 probably.

I think I tested my mux. strengths before and after adding the filter to the Mendip aerial and it made no difference. Have to re-test both, but it's hard to measure at all points without a proper meter.
My un-proper meter will probably be my Pi/DVB-hat powered from a power bank I just acquired.

Not that all of us have (or need) such filtering (yet).

Mine was speculative to prevent problems unexpectedly popping up at an inconvenient moment. For the sake of £8, or whatever it was, it's a no-brainer.

There are three of those masthead amps ins stock at CPC Farnell if you want some

I don't. I have a spare.

my aerial is in the loft near a 13A twin socket.

Is that (ahem) a tap off the lighting circuit or via a proper feed?

 

[Owen Smith]

Is that (ahem) a tap off the lighting circuit or via a proper feed?

In my loft I have both! The lighting circuit tap is a single socket and clearly labelled as lighting, it is for the power supplies to my mast head amps.

The other one is a double socket I put in on the 20A feed for the air conditioning I had installed 10 years ago. I put the power feed in for it and decided since I was running a 20A radial circuit through the loft I'd have some sockets on it.

 

[Last.To.Know]

So...

All my SD channels are breaking up and are unwatchable.

Apart from the 3 that are on the PSB3/BBC B Mux.

HD channels are fine.

Live readings from the TV interface are:-

Channel	Frequency	Signal Strength	Signal Quality	Network	Mux	Type
21	474.0 MHz	80%	100%	Cambs & Beds	PSB3/BBC B	DVB-T2 (HD;6)
24	498.0 MHz	83%	50-90%	Cambs & Beds	PSB2/D3&4	DVB-T (SD;2)
27	522.0 MHz	85%	50-90%	Cambs & Beds	PSB1/BBC A	DVB-T (SD;2)
33	570.0 MHz	84%	30-50%	Cambs & Beds	COM4/SDN	DVB-T (SD;2)
36	594.0 MHz	85%	40-90%	Cambs & Beds	COM5/ARQ A	DVB-T (SD;2)
48	690.0 MHz	64%	30-50%	Cambs & Beds	COM6/ARQ B	DVB-T (SD;2)

The signal quality is oscillating wildly between the two values.

The SD channels looks great on my TV so...

Questions:

Any idea what this might be?

Should I do a retune?

Should I NOT do a retune?

Any help gratefully received.

 

[prpr]

Those signals are very high level. You haven't said what your "signal amplifier" device is, or how much gain it has (can you provide a picture?), but I suspect it is either too much or it's unstable (maybe both). Can you bypass it and repeat the readings? How is the TV fed? How is the Humax fed? Can you swap them between the feeds?
Do NOT retune.

 

[Last.To.Know]

Thank you for the reply.

I will do the bypass tomorrow.

The chain of command is

Aerial > Restoretv.uk filter > signal amplifier > Humax > TV (I think).

I will check that tomorrow.

 

[Last.To.Know]

Didn't realise signals could be too high?

Here is the signal amplifier



Oddly, the SD channels improved last night.

And when I look at them now, they seem fine.

I won't bypass the signal amplifier as I wouldn't be able to detect any difference in picture quality.

 

[prpr]

Didn't realise signals could be too high?

Everything has a limit.

Here is the signal amplifier

That's not the amplifier. That's the power supply for the amplifier, which presumably is somewhere remote.

Oddly, the SD channels improved last night.

Magic? Mystery? Voodoo?

And when I look at them now, they seem fine.

Until the next time they aren't.

I won't bypass the signal amplifier as I wouldn't be able to detect any difference in picture quality.

Huh? It doesn't do anything to picture quality, and if you can't tell if it's doing anything then you don't need it.

Why is this always like pulling teeth? Forget it then.

 

[MartinLiddle]

I won't bypass the signal amplifier as I wouldn't be able to detect any difference in picture quality.

This is digital TV, the picture quality shouldn't be influenced by the signal strength providing it is neither too high nor too low. I would suggest a signal strength between 50% and 90% will result in the same picture quality.

 

[Last.To.Know]

It's like pulling teeth (to you) because you know what you know and I don't know what you know or need to know.

We were discussing picture quality.

Is it such a leap to think that's why you asked about the signal amplifier?

 

[Last.To.Know]

Thank you, Martin.

May I tentatively ask, what is the purpose of amplifying the signal?

Presumably, as it's digital, it's to get it above a certain minimum threshold?

 

[Black Hole]

Didn't realise signals could be too high?

If a signal is strong enough to saturate the input, the electronics are driven into non-linear operation and all bets are off. Demodulation (extraction of the digital bit stream from the UHF carrier wave) produces either a perfect signal or nothing at all (unlike analogue).

The problem with trusting the signal strength figures from the HDR-FOX or a digital TV is that "100%" actually means ">99%" (with no upper limit), and we have no idea where saturation occurs. You can only really trust the quality figure (which is a measure of the amount of work the error correction is doing). However, even with strength figures below 100%, and even if we assume the HDR-FOX is not saturating at 100%, you don't know whether anything further up the signal chain has already gone into non-linearity.

Consequently, the use of signal amplifiers is not a no-brainer. They must be used appropriately, only when absolutely necessary. Using a one-output amplifier to launch a signal into a complex distribution network feeding multiple receivers (like me!) is asking for trouble.

All this has been discussed at great length in the past, and you've been around long enough...

 

[Owen Smith]

Didn't realise signals could be too high?

If the signal strength into the amplifier is too high, the amp will be unable to amplify it properly and the signal will clip inside the amplifier leading to distortion. This was very obvious on screen with analogue TV, it's harder to diagnose now with digital.

Your signal strengths are high but not excessively so in my view. I have that sort of signal strength from Sandy Heath, where the usual problem as you have is COM6 is considerably weaker. I have a 13db mast head amp because if I don't I can't receive COM6, everything else is fine without the amp.