Poor quality signal through TV booster

An interesting problem with my parents TV reception occurred a while back.

My parents set-up was as follows. A high gain digital TV aerial on the roof, pointed towards the Belmont transmitter. This fed into a 6-way TV booster in the loft, which supplied TV signals to outlets in the 3x upstairs bedrooms,

2x outlets to the living room (front and rear) and to 1x outlet in the back/dining room.

The TV booster had a Wickes badge on the front, but was manufactured by Labgear. It was one of their older models which I had installed back in

1990, but the digital TV reception through it had been fine, up until a few months ago....

Then one day, the reception went on several of the channels. BBC1 & 2 was poor, but ITV and CH4 & 5 seemed OK. Checking the signal strength on the sets, the strength was quite high (90%) but the signal quality was poor. Even on the good channels, quality was only about 20%, despite the strength being over 90%.

The one exception being the set in the back/dining room, in which the reception was perfect and signal strength and quality were both around 90%, which was odd.

I actually found that the reception on the other sets was fine when the outlets where linked direct to the aerial and not through the booster.

Anyway, have replaced the old booster with a new one, think its a Tri-star model, which I got from B&Q (think they're made by Philex?) and reception on all sets is now excellent.

What I was curious about though was firstly, was this simply a case of the old booster developing a fault, or or was it that they altered the digital broadcast somehow (upped the power, changed the transmission frequencies or something) a few months back that was causing some sort of interference with the booster, due to its age? In either case, how come the reception was fine on the set in the back room?

Any thoughts on this? Just trying to make sense of the anomalous results I got.

Reply to
Simon T
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It could have been a solder joint on the booster's PCB gone bad.

Reply to
Davey

Depends a bit where you are. My parents high gain antenna catches the Welsh transmitter in a sidelobe and their daft old Panasonic TV puts first found into the standard channel positions. Which means all channels turn into Welsh if an autoretune occurs (now disabled).

It was fine until D-day when the Xmit power levels were increased.

It is possible that when digital switchover occurred and they boosted the Welsh transmitter power significantly that this could lead to intermodulation distortion in your ageing booster amplifier.

It could be that the booster has gone bad. Does it still ruin the signal if you interpose it in the new signal path at the TV end?

Or do the TVs that coped still cope and those that didn't still fail?

Some TVs are tetchy about signal levels and will misbehave if the aerial input signal is too strong as well as too weak.

Reply to
Martin Brown

If it was suddenly and fairly recently could it have been anything to do with 4G being enabled on a local phone mast? I cant say why this wouldn't have affected everything equally other than perhaps different cable lengths being affected differently by the interference? Its just a guess but your new booster may have a 4G filter built in.

Reply to
CB

I've just had a secondary Labgear booster die. Been in service for maybe 5 years, first one I've ever had fail. Fortunately I always buy these things for stock, so there was a spare one on the shelf. The original Labgear loft booster is now 42yrs old and going as good as new!

Reply to
Capitol

I would suggest that the booster developed a parasitic oscillation that would substantially increase the noise floor.

Why the two TVs have different symptoms is less clear, perhaps the receivers have different performances and the lengths of cables may have a bearing through different filtering characteristics.

Reply to
Fredxxx

DIY amps often develop a fault in which the smooth DC generated internally has ripple on it. This superimposes a waveform on the muxes which affects different TV sets to different degrees. Some TV sets can be unaffected. An affected set will typically show good strength but poor or fluctuating quality.

Or it could be 4G or some other strong signal swamping the old amp. Many of the older amps are an open door from 40MHz to light.

Bill

Reply to
Bill Wright

Thanks for the replies everybody.

I'll put it down to the old booster developing a fault then.

Again, new booster is working nicely. So hopefully there will be no more problems for a while.

Reply to
Simon T

Roughly how far from the 4G transmitter to be safe from this?

Reply to
bert

Spot-on Bill, as usual. The PSU in those amps was just a mains transformer, bridge rect, reservoir cap and 78xx regulator. Almost certainly the reservoir cap has failed o/c. Very simple to repair, of course.

True, 'light' being about 2GHz in this case. However if an 800MHz 4G base station has come on-air nearby it's likely the OP would have had a postcard from 'at800' offering a free filter.

Reply to
Andy Wade

Well assuming the cables are still the same ones as before, it kind of sounds like the outputs or at least some of them weere faulty. Normally though, as has been noted before, its normally input overload whether it be by 4G or other transmission that causes poor quality reception. Brian

Reply to
Brian-Gaff

En el artículo , Simon T escribió:

My money would be on bad caps in the booster power supply. The age is about right, and it's been hot recently, which will have hastened the demise of the booster with it being in the loft.

The one problem-free output is harder to explain away - perhaps it's a direct feed from the aerial and is not actually amplified.

Reply to
Mike Tomlinson

You may recall I had a similar problem with a (decent) Labgear amp when I moved in here. Good enough levels coming out of it, but poor quality. Looking at an analogue channel at the time, you could see a noise pattern in the output that was similar to "run through" from an adjacent out of sync channel[1], however in this case it was fixed in position and not moving at all.

[1] Horizontal bar about 1/10th screen height, and a narrower vertical one offset from the left of frame.

Replaced it with a passive splitter and a variable gain proception masthead amp. Been fine ever since.

Reply to
John Rumm

The beauty of analogue was that the trained eye could see what was wrong, well-nigh immediately. Digital just falls off its cliff.

Cross-mod, by the sound of it.

I think the Proception amps are proving pretty reliable. The mains-powered units all have decent quality 105 deg caps in the PSU. I've got an early prototype in a friend's loft that's been running continuously since 2004 and still seems OK. But MRD applies... :~)

Reply to
Andy Wade

In article , Mike Tomlinson writes

I've recently started having problems with Freeview signal dropping out esp at daytime on some channels. As a result of this thread I've swopped round the outputs from my booster amp and now it's OK - (except for the (unused) socket which is now fed from the faulty output)

Reply to
bert

bert posted

Yes, me too. BBC1 often becomes unwatchable in the morning and early evening.

I don't have a booster amp, just a standard loft aerial. We have an 80% strength signal from the Honiton transmitter, but quality spasmodically drops below 50 per cent.

Reply to
Big Les Wade

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