Basic rate ISDN lines usually have a locally powered (ac mains wall wart
etc) NT at the customer premises-if the power goes off this will stop
'talking' to the exchange end-which it is normally doing on a continual
basis-even if no calls are established.
Pair gain systems (0+2, etc), on the other hand- usually are powered from
the exchange end, and would keep running despite local power being off.
The former would be unusual in a suburban environment- the latter may be
quite common.
Whether or not this info is relevant is another matter!
73
Dave, ZL3FJ
----- Original Message -----
From: "g3ldo" <[email protected]>
To: <[email protected]>
Sent: Thursday, June 10, 2004 8:57 PM
Subject: LF: Re: Re: Re: Off Topic---QRM
Alan Melia said
> Hi Peter, the immediate thought is DSL ( or ADSL) or even ISDN lines. I
> would not lay too much store by BT "engineers" not being able to find
it.
> These guys have little or no RF experience in general. Because it is so
> wirespread, I would suggest it is a system effect rather than a fault
> somewhere, and it would seem to correlate with the increased penetration
of
> "broadband". This could explain why some "diss poles" are not as noisy
as
> others.
Many thanks to Alan and the rest of you who responded regarding my QRM
problem.
I don't think that the noise is generated by BT even though it is being
radiated by some of their distribution systems.
Last week we had a power cut that affected an area of around one or more
km
radius and the noise (almost) disappeared. I think most ISDN etc is
powered
from the exchange.
All the interference comes down the antenna. I can reduce it considerably
by
parking my beam so that the deepest null is on the source of the noise.
The
noise is very broadband (I can hear traces of it on the 10 and 18MHz band)
and is average S7 throughout the 14MHz so not an apparent harmonic.
Peter, G3LDO
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