Persistent Pixelation on Playback

[Owen Smith]

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

At my parents it's so the TV still works when my mum uses her hair drier. Without the amp the picture is fine the rest of the time and breaks up into a mess of pixelisation with the hair drier on. This is all with double screened CT100 coax, F connectors on everything and all cabled for digital from scratch. I use a 6db attenuator (F connectors) into the input of the HDR Fox T2 otherwise the signal strength goes over 100% at times and while it works it doesn't seem the best idea. Impulse interference seems less with the attenuator too. I'm aware I'm close to over amplifying the signal but mum won't change her hair drier.

 

[Last.To.Know]

Thank you all for your replies.

Here are photos of attachments to my aerial mast.



They are about 10 foot off the ground so this is the best I could do.

 

[prpr]

We were discussing picture quality.

No we weren't. You were complaining about reception issues/breakup i.e. decodability, which is not the same thing.

Anyway, the filter you have installed is downstream of the amplifier and therefore not doing its job before the signal gets scrambled in the amp.
I guess you put it between the power supply and the amp. too, which means it's being cooked by the power supply.

How old is all that stuff on the mast? From the analogue days? And what are the two units? One's the amp. (probably with a huge amount of gain), but what's the other?
I would suggest you don't need any of it. If you do, can it be put inside (loft?) where you can a) get at it, and b) get the filter between the aerial and the amp/Humax? I would replace it all with a modern low-gain amp. (as discussed previously), but only then if needed. Try it without first.
Until you do, nothing will improve and you'll suffer from intermittent reception problems, as you've already demonstrated.
I wonder if you can get the Restoretv people to send someone to sort this, otherwise I think you'll have to get someone in yourself.

And it's all oh-so-lovely with that tape holding things to the mast. This all demonstrates the usefulness of photos over words.

 

[prpr]

what is the purpose of amplifying the signal?

The sole point of it (apart from what Owen said, which is perfectly valid) is to overcome downstream losses, either in cables or splitters. As you apparently don't have any of the latter, then just the cable.
Whether you need one or not depends on how much signal you have to start with (from the aerial) and how much loss there is in the cable.
If you are getting closer to the cliff-edge of the decode margin at the receiver (the Humax in your case), then you need the amp, otherwise not.

 

[prpr]

breaks up into a mess of pixelisation with the hair drier on.

This reminds me of the effects of the 1970s.

mum won't change her hair drier.

Love to see a picture of it. In our case back then, it was mum's from the 60s or perhaps earlier, but thankfully it eventually broke.

 

[Last.To.Know]

All of the equipment, including the amplifier, was installed by the aerial installer.

It's from around 2004-ish so early FreeView.

I do not know what they are or do.

The only installing I have done was to install the filters.

When the reception issues return I will remove the amp (white box) from the chain, so that I can see the difference.

 

[prpr]

As already explained, the white box is the power supply for the amp, not the amp.
If you remove the power supply, the amp is, er, obviously unpowered. It may pass an unknown amount of signal under such conditions, possibly none.

This is what restoretv says (they make it difficult to copy, and with my emphasis, as already stated):

"If you have a weak TV signal, or several TVs, you may have a TV splitter, amplifier or booster in your loft or on your roof.
In this case, a Restore TV filter needs to be connected between the aerial and the amplifier. If you have a rooftop amplifier, a weather-proofed Restore TV filter will need to be installed. If you are responsible for your own aerial and, if you are eligible, we can arrange for a Restore TV engineer to visit your home and fit a filter for you at our expense.
Please note, our in-home engineer support is only available for individual households that solely rely on free to view services that are received through a domestic (rooftop or loft) aerial and have no access to cable and satellite services."

 

[Owen Smith]

All of the equipment, including the amplifier, was installed by the aerial installer.

Then don't use them again, they've done shoddy work for you. I suppose there is an outside chance they've learned something since then.

It's from around 2004-ish so early FreeView.

Given the state it's in I'm surprised it is that recent. It all looks well past its sell by date. This may need a new installation.

What state is the aerial in? If it's as bad as the amp and other stuff on the pole then you may be best off going for total replacement of the entire system. I have fears about the coax too, especially since there are two different colours of sheath so it's probably a rework of an even older system.

I do not know what they are or do.

The top one in the metal box is probably a filter and is in the correct place in the signal chain, trying to do a similar job to the one you added but as it is older it probably does not filter out 5G. Likely it's a Group W filter given you appear to be on Sandy Heath and in the old pre DSO days it had a mux on UHF channel 67, which was a complete pain to receive reliably.

The only installing I have done was to install the filters.

Take them out, where you have put them after the amp they do more harm them good.

When the reception issues return I will remove the amp (white box) from the chain, so that I can see the difference.

Likely that will be spring when the leaves start to grow on the trees and the sap rises, if you have trees in your aerial path. Failing that it will be next time we have distant propagation atmospheric issues.

 

[Owen Smith]

This reminds me of the effects of the 1970s.

Oh god don't remind me. I grew up during the 1970s and interference from all sorts of appliances was a constant issue.

Love to see a picture of it. In our case back then, it was mum's from the 60s or perhaps earlier, but thankfully it eventually broke.

The hair drier is from the 1990s. That said where mum dries her hair the TV coax runs about 4 feet above her head in the ceiling. If I could have bought something tripled screened I would have.

 

[Black Hole]

Anyway, the filter you have installed is downstream of the amplifier and therefore not doing its job before the signal gets scrambled in the amp.

Is it though? If the big box is the amp and the small box is the filter, it looks OK to me.

 

[Last.To.Know]

prpr - Thank you. I will explore the Restore TV site.

I do have a satellite dish which feeds into an ancient Sky box that I never use.

That may be their reason not to help me.

Owen Smith - Took the aerial out of the power block and plugged it directly into the Humax
Got the "signal too weak" message both with and without the filter.
Plugged the aerial without the filter into the power block - still no joy.

Restored the original set up including the filter and the picture is fine.

I realise that might be temporary.

Might try that all again tomorrow.

 

[Luke]

Took the aerial out of the power block and plugged it directly into the Humax
Got the "signal too weak" message both with and without the filter.

I have yet to see online anyone reporting that an unpowered masthead amplifier still has enough signal get through for the TV to be watchable.

As previously explained by prpr

As already explained, the white box is the power supply for the amp, not the amp.
If you remove the power supply, the amp is, er, obviously unpowered. It may pass an unknown amount of signal under such conditions, possibly none.

It's a bit like trying to use your HDR-FOX T2 to pass an aerial signal to your TV when the HDR-FOX T2 is unplugged.

 

[prpr]

I have yet to see online anyone reporting that an unpowered masthead amplifier still has enough signal get through for the TV to be watchable.

I recently discovered that the one I installed about 40 years ago actually does when I turned the power to it off for other reasons.
The level appeared to drop by the amount of gain it was putting in when powered. I was expecting the signal to drop below threshold, but the Humax kept on working.
Certainly had my money's worth out of that one, and its (still original) power supply.
(It's got two outputs, so I can't just remove it and put a splitter in, as that would take things too close to the edge further downstream via the 2nd output.)

 

[Owen Smith]

I have yet to see online anyone reporting that an unpowered masthead amplifier still has enough signal get through for the TV to be watchable.

I have one, but it's an advertised feature that it passes the original signal if the amp is not powered. That is the MRD aka Margin Rising Device aka 13 db amp to you and I that is fitted directly to a Televes DAT75 in my loft, you take the original "bow tie" receiving thing out and insert this "bow tie" plus amp in its place:

TELEVES 5050 MRD PREAMPLIFIER-DAT45 ANTENNA-Aerial Fixing Accessories- (Qty:1): Amazon.co.uk: DIY & Tools

TELEVES 5050 MRD PREAMPLIFIER-DAT45 ANTENNA-Aerial Fixing Accessories- (Qty:1): Amazon.co.uk: DIY & Tools

www.amazon.co.uk

I know the tri boom aerials over state their performance. If I was starting again I probably wouldn't end up with this system. But it was pre DSO and I was having trouble receiving UHF 67 from Sandy Heath and this aerial has highest gain at highest channels. Plus in my loft I can accommodate a tall aerial easily but not a long aerial, so the DAT75 fits a lot better than 18 element X bay aerials. It is working well so I am not messing with it, the money and time was spent around 20 years ago.

EDIT: my house is the middle of a row of 4 so I have no gable end and I also have no chimney, so it would be very difficult to install a TV aerial externally. If I could I probably wouldn't need an amp at all, I'm probably losing more than 13db going through the concrete roof tiles.

 

[Black Hole]

it passes the original signal if the amp is not powered.

Relay?

 

[Owen Smith]

Relay?

EDIT: (I thought you wrote "Really?"). I tried it and works as advertised. No there isn't a relay on the PCB.

 

[Black Hole]

I wonder how the heck that works then. I would have thought providing any kind of passive bypass would simply produce a feedback loop around an amplifier! Maybe there's a depletion-mode FET acting like a relay.

 

[Owen Smith]

I wonder how the heck that works then. I would have thought providing any kind of passive bypass would simply produce a feedback loop around an amplifier! Maybe there's a depletion-mode FET acting like a relay.

I have no idea. I only know there is a tightly packed surface mount PCB in the metal box in the middle.

The aim is to allow people to put the aerial up with the MRD installed and then put the power supply in to it later. This is exactly what we did at my brother's house, he put the aerial up when he had some scaffolding and mates round to help and I came months later to put the distribution system in including power for the MRD. My brother's TV still worked in the intervening period.

 

[Black Hole]

to put the distribution system in including power for the MRD. My brother's TV still worked in the intervening period.

Surely under those circumstances, with no masthead amplifier needed to get a signal, it would be better not to have the masthead and use a distribution amplifier.

And in situations where a masthead amplifier is essential, the only point of having it pass through when unpowered is to be able to use a signal meter (if the signal meter registers at all!).

 

[Owen Smith]

Surely under those circumstances, with no masthead amplifier needed to get a signal, it would be better not to have the masthead and use a distribution amplifier.

And in situations where a masthead amplifier is essential, the only point of having it pass through when unpowered is to be able to use a signal meter (if the signal meter registers at all!).

This was in the analogue days and my brother lives in a valley in Kirkburton with lots of complex hills. He has no line of sight of Emley Moor but the signal strength from Emley is so strong that he got multiple reflections all being received by the crap "low loss" coax buried in his walls that he couldn't replace without destroying half the house decorations. On his TV you got about 4 ghost images almost as strong as the real image. So the plan was to put as strong a signal as possible into his distribution system without clipping so the real signal was a lot stronger than the ghosts. The MRD amp on the DAT75 aerial plus double screened coax on the aerial feed into the loft into his distribution system did the trick, much better analogue picture with no ghosting and my brother was very happy. I also replaced his distribution system for a passive F connectors metal screened 4 way splitter, the stronger signal from the aerial was causing clipping in the old distribution amp. As a bonus it worked perfectly for pre DSO digital which was never part of my brother's requirements, and continues in use unmodified to this day.

That's about 25 years service now, indeed it's probably time it was inspected but I don't fancy climbing on his roof. Plus the only thing outside is the DAT 75 aerial with MRD fitted (which has a conformally coated PCB I believe) and the double screened coax down into the house. Everything else is inside, both myself and my brother wanted that. The coax looks intact through binoculars.