[Dave Plowman (News)]

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. ;-)

--
*Two wrongs are only the beginning *

Dave Plowman London SW
To e-mail, change noise into sound.

[tony sayer]

In article , Dave Plowman (News)
scribeth thus
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. ;-)

What make and model of amp is it. I suspect that its overloading what
with where you live etc Dave...
--
Tony Sayer

[Andy Hall]

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.

[Dave Plowman (News)]

In article ,
tony sayer wrote:
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. ;-)

What make and model of amp is it. I suspect that its overloading what
with where you live etc Dave...

Thing is these problems are recent - it all used to work just fine. But I
tried a plug in attenuator (6dB) which made no difference.

The DA is a Mini4 made by Fringe Electronics and is pretty old.

So I popped out to TLC and got this one:-

http://www.tlc-direct.co.uk/Products/MXSLX4G.html

Which has done the trick.

--
*Being healthy is merely the slowest possible rate at which one can die.

Dave Plowman London SW
To e-mail, change noise into sound.

[Dave Plowman (News)]

In article ,
Andy Hall wrote:
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.

I'm wondering if the DA itself is hooting. Not got anything here that can
check those sort of frequencies. My 'scope does go up to 100 megs, but
I'd not know what to look for. It does show noise with the input
shorted, though.

--
*If Barbie is so popular, why do you have to buy her friends? *

Dave Plowman London SW
To e-mail, change noise into sound.

[Andy Hall]

On 2007-09-19 14:43:50 +0100, "Dave Plowman (News)"
said:

In article ,
Andy Hall wrote:
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.

I'm wondering if the DA itself is hooting. Not got anything here that can
check those sort of frequencies. My 'scope does go up to 100 megs, but
I'd not know what to look for. It does show noise with the input
shorted, though.

Exactly.

I don't have the high signal issues that Tony alluded to - it was the
DA that was taking off. This was creating wideband crap as well as
interference but also it was still kind of working. Of course it
may have been that it was providing no gain as opposed to some gain.

[tony sayer]

In article , Dave Plowman (News)
scribeth thus
In article ,
tony sayer wrote:
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. ;-)

What make and model of amp is it. I suspect that its overloading what
with where you live etc Dave...

Thing is these problems are recent - it all used to work just fine. But I
tried a plug in attenuator (6dB) which made no difference.

The DA is a Mini4 made by Fringe Electronics and is pretty old.

So I popped out to TLC and got this one:-

http://www.tlc-direct.co.uk/Products/MXSLX4G.html

Which has done the trick.


Fine must have been something really odd with it.

A bad case of electrickery flowing uphill perhaps...
--
Tony Sayer

[tony sayer]

In article , Dave Plowman (News)
scribeth thus
In article ,
Andy Hall wrote:
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.

I'm wondering if the DA itself is hooting. Not got anything here that can
check those sort of frequencies. My 'scope does go up to 100 megs, but
I'd not know what to look for. It does show noise with the input
shorted, though.


Wonder if somewhere there is a line powering switch thats been put on by
mistake?...
--
Tony Sayer

[Dave Plowman (News)]

In article ,
tony sayer wrote:
I'm wondering if the DA itself is hooting. Not got anything here that
can check those sort of frequencies. My 'scope does go up to 100 megs,
but I'd not know what to look for. It does show noise with the input
shorted, though.


Wonder if somewhere there is a line powering switch thats been put on by
mistake?...

There is indeed an internal one but it was off - and to make sure I
checked the aerial socket.

I'll take it into work on Friday and look at it on the spectrum analyser
there. Or to be truthful ask one of the engineers to do it. They tend to
be pretty hot on RF - lots of radio mics and walkie talkies etc to fix.

--
*Why is it that to stop Windows 95, you have to click on "Start"?

Dave Plowman London SW
To e-mail, change noise into sound.