Ping Bill Wright and anyone else able to troubleshoot TV signal issues

[F]

We have a five-in eight-out (Triax?) multiswitch in the loft, receiving signals from a satellite dish and a terrestrial aerial, and feeding eight triplexer plates. Three of them have Humax Fox-T2 HDRs connected and one of them an LG OLED TV.

From time-to-time (like last year, last week and today) the Humax boxes report no signal on BBC News (107) and all of the other channels broadcast on the same MUX(?). Manually retuning channel 32 (562000kHz) has no effect and the signal strength and signal quality are reported by the boxes as 0%. At the same time, the TV shows 90% signal strength and

100% signal quality, and displays the programming. Swapping over the two aerial leads from the wall plates makes no difference. A 'professional' meter on them shows a signal strength of 48-50dB.

Eventually, after hours or days, and without any more interventions, the Humax boxes start to show their usual ~60% signal strength and 100% signal quality and the programming returns to normal (though not all of the boxes return at the same time).

Oddly enough, today, for the first time, the TV has had the same issue though only a couple of times and only for only a second at a time.

Any thoughts on what the problem might be, along with a fix, would be welcome!

[F]

Forgot to say: we're on Emley Moor!

[Brian-Gaff]

Signal blocking at the tuner inputs, ie overload of some signal from wherever perhaps. The better the quality of the receiver the less the effect perhaps? Brian

[Bill Wright]

It shows up intermittently on one mux only for now, but that doesn't actually narrow it down. Strange to tell, this could be: dish alignment dish damage signal obstruction polarity offset faulty LNB faulty cable Faulty multiswitch local interference.

You need to get an analyser on it. Start at the top and work down.

Bill

[Andy Burns]

I know he said it fed into a multiswitch, but huh?

[F]

Thanks Bill but, unless I've misunderstood you, it's the terrestrial signal that goes AWOL.

[Bill Wright]

Yes sorry. I was a bit drunk. It was a hot day. I'd been strimming. But if you translate my remarks into terrestrial terms they still apply!

Is the aerial suitable for ch32? Are you using a Gp B aerial (as in days or yore)?

I'm still using a Gp B for Emley and the level on 32 is significantly low.

It sometimes happens that trees bugger up (technical term; google it if necessary) reception starting at this time of year, even when it's never happened before. Do you live in a dense forest? Or do you have a tree nearby?

You still need to check the signals with an analyser. If you're getting

50dBuV at the outlet you need to consider the gain of the switch before assuming the aerial signal is OK. If it's one with variable gain, how is it set? I vaguely remember that some Triax switches have/had zero gain but a variable attenuator on the terr input.

Bill

[F]

Glad to know that you had a Bank Holiday drink!

How do I check if the aerial is Gp B? It's around 6 years old if that's relevant.

No trees, or anything else, in line-of-sight.

I'll get up into the loft to check out the multiswitch (Christmas paraphernalia permitting!).

[Andy Burns]

Can you see a coloured bung in the end of the tubing?

[Andrew]

A significant percentage of the UK male population are RED/GREEN colour blind.

Bad news if you need a Group A aerial and end up with a Group C/D one, or vice versa :-)

- though the element spacing should help them.

[ARW]

Any solar panels in the way?

[Bill Wright]

Not infallible alas.

Bill

[Bill Wright]

You post a picture of it here. Don't expose for the sky. Take a close up and one that includes brickwork or similar for scaling.

Bill

[F]

Thanks, I'll do that tomorrow (it's dark now I've finally got round to Usenet!).

[F]

Yes, on the roof in front(ish) of the aerial. They can make a difference?

[F]

These any good?

[Mike]

A few years ago I lost one channel due to an oxidised connector. The other channels were fine. Remaking connector fixed it.

[ARW]

I was hoping Bill would no the answer to that:-)

[Bill Wright]

It's a Vision V10. Wideband presumably. I don't know if Vision ever made a grouped version. If they did it wasn't popular. It isn't a very high gain aerial; nor is it particularly directional.

The solar panels won't have any effect.

The wall fixing is inadequate for the load, because of the FM aerial (which is Antiference.) It would even be verging on being inadequate if there were four wall bolts (there are only two I think, which is terribly naughty).

Bill

[The Other Mike]

But what about the inverter that could be located in the loft adjacent to the aerial / coax / multiswitch? They certainly have the potential to disrupt broadband signals albeit a few hundred MHz below Band IV and V.