RE: [OT] Interference help please !!

["Keith Doxey" <ukha@xxxxxxx>]

Hi Dean,

> -----Original Message-----
> From: Dean Barrett [mailto:dean@xxxxxxx]
> Subject: [ukha_d] [OT] Interference help please !!
>
>
> We have a problem in a couple of houses where the customers have
> interference on the telephones. Its not a crackle type intereference
but a
> humming that comes in and out, we believe there may be 3 houses in a
row
> that are suffering the problem.
>
> We intially thought it was mains born int. from BT's possible trapped
> against mains, but the humming continues to pulse in and out without
any
> power on in the house at all. We then found that adjacent house
> had exactly
> the same problem.
>
> There is no problem on the BT master, so we assume our cables are
> working as Aerials and picking something up.
>

You say there was no interference at the NTE5. Presumably this was with al
the customers internal wiring disconnected. What phone did you use for the
test?

If the customers wiring is connected with NOTHING plugged into any of the
sockets, is it still clear at the NTE5. ?

If it is still clear, then using the SAME PHONE, are all the other sockets
affected ?

If it is still OK then it is possible that one of the phones or other
pieces
of equipment connected to it is causing the problem.

A phone line is a balanced line and unless there is a fault causing
imbalance eg earthing on one wire, the it should be maily free of
interference even though it may be several miles from the exchange.

Certain phones are more prone to hum pickup than others, it may be the
phones that are succeptable. I have experienced phones where the amount of
hum increased as you get closer to the mouthpiece.

Does the hum fade in and out or does it appear in bursts eg
MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
<period of silence>
MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM

if so there could be somewhere nearby using RF Welders. I have also heard
sound systems that suffered from a hum when a radio transmitter was
operated
nearby. This was a "temporary" (well alright 'Pirate') radio
station in a
holiday chalet next to the chalet used by the security guards. Everytime
they used their two way radios there was an audible hum on the disco gear
being used for the station.

It could be coming from almost anywhere and could take some time to track
down.

Sorry I cant help more

Keith