On 02/07/2015 21:59, Simon T wrote:
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.

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.

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.

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.

--
Regards,
Martin Brown