On 2007-09-19 09:57:09 +0100, "Dave Plowman (News)"
said:

Just as an update I've played around with this most of yesterday and
concluded it's the DA that's faulty. Although not sure exactly what the
fault is.

I changed the DAB aerial back to the FM one - mounted vertically.

There are four tuners - two DAB, two FM, fed via a DA.

DAB now fine - FM noisy. Aerial horizontal DAB poor FM fine.

With the aerial vertical plugging the aerial direct to any tuner - fine.
Horizontal - FM fine but DAB marginal on only one of the DAB tuners -
other one fine.

So either the DA is faulty - although it appears to be increasing the
signal level - or one of the tuners is *transmitting* a nasty back up the
line?

I'm rather lost with RF. ;-)

I had one at one point that developed some fault that caused it to
start oscillating at around 350MHz. The net result was that there was
a lot of apparent noise and crud on FM and again on the lower channels
of UHF (i.e. Crystal Palace). Higher UHF channels were OK. It
took an installer with a rectum paralyser (sorry spectrum analyser) to
detect this. Amplifier was swapped and all was well.

If one of the tuners is doing something, then turning devices off in
sequence should find it.