TV aerial boosters, revisited

[Adrian]

Back in the winter of 13/14, we had a long and useful thread on here following my house-move to the wilds of Herefordshire (Much Marcle/Ridge Hill transmitter)

At the time, we'd got fun'n'games with some channels, usually the Beeb mux, going awol in the evening. It's continued, especially in winter.

We've recently bought a new TV, though. A modern thing, without a tube. It's magic, I tell you!

And I'm in trouble.

It won't find the multiplex carrying ITV3. And ITV3 carries Midsomer Murders... We had a good signal for that before. It's all my fault, y'know.

DigitalUK tells me that I should be getting "yellow/variable" coverage on that mux. This TV reports signal strengths and quality for each mux in the manual tune.

Ch21 - SDN/COM4 - is the offender. I see 0% signal strength, occasionally bipping up to 5%, with 0% signal quality. DigiUK says "yellow" for this.

I'm also having problems with Ch22 - BBCB HD - again, zero, but bipping up on the strength a little more often and up to the heady heights of 15% or so. When we first tuned the TV in, we did get the HD BBC channels, but they went awol in a later autotune attempt. DigiUK says "green" for this.

Finally, 27 - ARQ B/COM6. I've seen as high as 90% strength, but still zero quality. DigiUK says "green" for this, too.

I'm getting all the other muxs just fine.

Back in that previous thread, the consensus was that our aerial was right. There are a couple of boosters - a Vision V23-100 and a Vision V52-100. Is it worth replacing them? If so, what with?

Thoughts, Gents, please.

[The Natural Philosopher]

Check aerial cables carefully.

I take it the aerial itself is the best you can get, suits the band and is installed and pointing at the transmitter?

[Tim+]

Why two? Not daisy-chained I hope?

Are these masthead ones?

Tim

[Bill Wright]

Isn't one of them just a PSU? Don't ask me to look it up, I'm retired.

Bill

[Adrian]

Yes, they are daisy-chained.

[Tim+]

I'm no expert but I was under the impression that that is A Bad Idea. If the signal is that weak you're just boosting the noise. No doubt Bill will say something a lot cleverer.

If you have a weak signal, one masthead amp is probably the way to go (assuming a good aerial).

Tim

[tabbypurr]

Bit hard to diagnose a system we know little about. But one principle might well get you there: test the signal at each point in the chain.

NT

[Chris Bartram]

I'm no expert either, but I'd agree. I'd start by making sure the antenna *is* the correct type, and aligned well. Check the condition of the coax, and and terminations you can get at (I'd guess the antenna itself is not easily accessible?), and try the TV without the boosters, if you can get at them.

*googles*

It seems the post above is correct, one's a PSU for a masthead amp, so scrub that. If you have a multimeter, you might want to see if you can measure 12v or so DC on the output of the PSU. Also have a look at Bill's article I found:

[Tim Streater]

Have you thought of adding Freesat? We just got that. It acts as a useful backup for the times when the Dover transmitter signal drops for some reason. And it gave us ITVPlayer.

Mind you, MM is going a bit wiggy. UFOs on the episode we watched tonight (on ITVPlayer).

[Terry Casey]

Well, according to Adrian in 2013, one was a PSU and the other is an amplifier. Vision no longer list it so we don't know the gain ...

Adrian, have you tried switching off the power to the PSU to see if anything changes?

If it doesn't it would point to one unit or the other being faulty ...

[tabbypurr]

or a bad connection somewhere between the two. Or a mains fuse open. Or a disconnected aerial. Or a disconnection or a short downstream. Or...

NT

[Brian Gaff]

Is it perhaps desensing due to 4G?? The amps could be being overloaded by those signals resulting in cross modulation and the drop in signal quality. Certainly cross modulation plays havoc with digital signals whereas before you just got herring bone patterns or floating sink pulses etc. Brian

[Brian Gaff]

[Adrian]

We don't even get a mobile signal good enough for SMS, let alone 4G.

[Adrian]

Yep, and I've just been fannying around on hands and knees swapping cabling about.

The first one, V23, is indeed a 12v 100mA PSU. The second one, V52, says it's a 2-way indoor amp. UHF 16-28db, VHF/FM

0-14db. There's two outputs, 0 and -14db.

Testing on channel 28, BBC A gives ~40% strength, 100% quality with everything as-was.

That's the ONLY combo that results in anything but 0 strength, 0 signal...

Turn 'em both off - 0/0 Loop one or the other out - 0/0. Swap the outputs on the internal over - 0/0.

So it looks like both are working - and both are needed.

I've not twiddled the adjustment on the internal, and I've not got the ladder out to go up to the masthead.

[Martin Brown]

Depending how old his old TV was that could be very misleading. The latest generation of digital sets have astonishing sensitivity. My parents will get the Wales transmitter nearly 50 miles away in a sidelobe of a high gain directional aerial pointed at Winterhill.

It could easily be overloading the front end or turning the otherwise adequate digital signal to mush via intermodulation distortion.

Not if it was made before the 4G frequencies were allocated it won't.

OP might be better off checking to see what he can receive on the new set with a wire coathanger or an indoor aerial if one is to hand.

My parents Panasonic set would pick up Winter Hill today with a piece of wire inserted in the aerial socket. Their original tube based TV and early digital decoder needed a new high gain antenna to work at all.

Local hill blocks direct line of sight to Winter Hill so aerial needed either to be on a very long pole and/or high gain to work. Modern set is so sensitive that signal level is no longer an issue. Quality score is pretty ropey with a wire in the aerial socket but it mostly decodes.

[Tim+]

Just to be clear, there's a power supply, an internal amp AND a masthead amp or are you just referring to the aerial cable connections up on the masthead?

Tim

[Adrian]

Removing all assumptions and SWAGs...

Looking up from the ground, I can see the cable comes from the aerial itself into a plastic thingy.

A cable comes out from the box and towards the house.

In one bedroom, a bit of coax comes out of a wall and into a plastic thingy containing a metal thingy marked up as a Vision V23, which says it's a PSU and shoves +12v back up that cable.

The output from that goes into another plastic thingy containing a metal thingy marked up as a Vision V52, which says it's an internal amp.

Two cables come from that, into the wall.

The TV plugs into an aerial socket on a different wall in the living room . There are similar aerial sockets in other walls, in the kitchen and at least two bedrooms, but I've not even bothered to try those, because I don't want a TV in those rooms.

Pissing about with the plastic thingies on the bedroom wall makes a difference to what the TV shows.

[Adrian]

The old TV had a tube and didn't know what digital was. The old DTV was a Humax from early-mid '00s.

The new TV is a smart LG.

I seem to have the opposite problem. Channels that worked fine before are no longer available. The aerial hasn't been touched.

Most muxs are fine, the other ones report a poor signal.

I don't have an indoor aerial to hand, and I'm somewhat reluctant to attack the new TV with a wire coathanger. In addition, it's at the "wrong end" of a house with big thick stone walls which stop DECT and WiFi signals perfectly effectively.

[Tim+]

Have you plugged your tv directly into either the feed from the masthead (via the PS) or directly into the second amplifier?

Just wondering as your second amp has only two outputs but you seem to have a lot more than two sockets which suggests that there may be a few passive splitters scattered around the system which might be degrading the signal in the living room.

Tim