I interfere with my own TV signal!!

I've checked all the connections and all are sound.
I've looked at changing it to three separate feeds and there isn't space down the conduit they run in for three. I could probably get two in but my downstairs neighbour isn't there until August so can't make those changes yet. Still looking like a cabling issue to you Winston1?

randers said:

I've checked all the connections and all are sound.
I've looked at changing it to three separate feeds and there isn't space down the conduit they run in for three. I could probably get two in but my downstairs neighbour isn't there until August so can't make those changes yet. Still looking like a cabling issue to you Winston1?

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With a bodge like that all sorts of mismatches and reflections on the cable can have those sort of effects.

If your neighbour is not there you could try disconnecting his feed temporary from the back of your socket and see if this helps. Then at least you will know.

randers said:

Hello again. I've been back at my flat for a few days and have found the problem's not resolved. But from what I've seen this week it seems that most channels are fine (have strength around 94 quality of 100 yet work perfectly), it's 3 specific channels which are sometimes on strength 18-22 and quality 100 and pixelate a lot or are on strength 0 quality 0 and show a bit error rate at the max and of course don't work at all at those times.
I've chatted to the neighbours at the other end of the aerial feed i.e. ground floor and they can't get those same three channels at all. Is there anything in that which suggests a specific problem to you?
I am really grateful for your help.

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There are several things going on, but we still haven't got the whole picture from you to enable anything more than best estimate. Anyway, based on what info we have so far...

Your neighbours below don't get these channels because the signal loses some strength due to the resistance of the cable in the drop from your flat to theirs. The signal is too weak for these channels by the time it reaches them. They get the good channels, and at sufficient strength that they think it's all okay.

Depending on your local transmitter, it could be that the channels you're struggling to receive are at frequencies where your current aerial just isn't that good at receiving them, or they could be broadcast on a lower power, or they're at a marginal range. It could also be that the loft install is responsible for 'lumpy' reception... Or maybe even a combination of all of these factors!


If I was facing this as a call from a property owner, and given the limit that rewiring to the individual flats isn't available as a possibility, then I'd look at two options:

The quick and cheap solution is to kill the troublesome channels by introducing an attenuator. None of the TVs would then see the transmissions. A 6dB attenuator would probably do the trick. It's then just a question of retuning the top floor flat TV to exclude the channel allocations.

The alternative is to look at the whole system (including measuring all the channel mux strengths) to see whether it's possible to receive these channels. If so, then to overhaul the entire installation. This includes looking at the matching of the aerial to the local transmitter and possibly changing the aerial to a better new fit. Then mapping the loft to get the best aerial location if an outdoor fit isn't a possibility. Finally, installing a launch amp and tap system so that all the flats get the same signal.


That's about as far as it's possible to get without knowing which is the local transmitter and the UHF Channel numbers of the various muxes, particularly the troublesome mux.

If this or any other reply was helpful to you, then please do the decent thing and click the T-H-A-N-K-S button. It appears when you hover the mouse pointer near the Quote Multi-quote buttons. This is the proper way to show your thanks for the time and help someone gave you.

Thanks guys I appreciate all the help. (Really. Not just saying it).
Since my last post the neighbours have told me they're happy with their situation, well not happy but they'll tolerate it, so they don't want to spend to sort out our common problem. So... I buy might buy a separate aerial for just me and give myself a separate feed into my flat. So can I ask one last favour - how do I identify a perfectly matched aerial for my local transmitter (Craigkelly. I could also use Black Hill but that'd put some big trees in the way so probably not a good idea). Thanks if there's a way for a layman to do it.
Cheers guys.

randers said:

Thanks guys I appreciate all the help. (Really. Not just saying it).
Since my last post the neighbours have told me they're happy with their situation, well not happy but they'll tolerate it, so they don't want to spend to sort out our common problem. So... I buy might buy a separate aerial for just me and give myself a separate feed into my flat. So can I ask one last favour - how do I identify a perfectly matched aerial for my local transmitter (Craigkelly. I could also use Black Hill but that'd put some big trees in the way so probably not a good idea). Thanks if there's a way for a layman to do it.
Cheers guys.

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Craigkelly was a group A transmitter, but now com 7 & 8 use ch 55 and 56 so a wideband aerial must be used. A good log periodic would be my choice of aerial.

Craigkelly info is here. Scroll down the page to the table headed 'Digital television'

In that table you'll find the UHF channel numbers for the various muxes. The bulk of them start at Ch21 and go to Ch37. This corresponds with a Group A aerial. However, there are two out on their own. These are Com7 and Com8 on channels 55 and 56 respectively. They are out of band for a Group A aerial, so you won't get them.

Coms 7&8 are temporary. They're a stop-gap solution whilst all the channel re-jigging is being done for the 700MHz band clearance to accommodate 5G mobile phone signals. Longer term (past 2020 I think), the plan is to switch them off and fold the channels in to the existing commercial muxes. The Government's idea is that by then enough people will have TVs that include a HD tuner so that it won't matter so much if the SD channel versions are scrapped. That's a bit of a gamble though. The people at Arqiver (the company that runs all the transmitters) doesn't share the Government's optimistic view.

Once the 700MHz clearance is complete (2020), then the space for the current Com 7 & 8 muxes will no longer be available. They'll have to go somewhere, but where is a very good question.

As of this moment, you could use a Log36 aerial (a Log Periodic aerial) which will cover the entire channel range from 21 up to 56 and a bit more, or you could go for a DM Log. A Group A aerial would give you a stronger signal levels for UHF channels 21 to 45/46, but be no good for the Com 7 & 8 muxes, so I don't think that would be a sensible choice in the short term. More aerial and group info here


If this or any other reply was helpful to you, then please do the decent thing and click the T-H-A-N-K-S button. It appears when you hover the mouse pointer near the Quote Multi-quote buttons. This is the proper way to show your thanks for the time and help someone gave you.

Once again, thanks to you both!