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RE: [RFI] RFI to intercom

To: "Van Fair" <giw@bellsouth.net>, <rfi@contesting.com>
Subject: RE: [RFI] RFI to intercom
From: "EDWARDS, EDDIE J" <eedwards@oppd.com>
Date: Mon, 23 Aug 2004 08:11:10 -0500
List-post: <mailto:rfi@contesting.com>
Sounds like it might simply be audio rectification of your RF signal
picked up by the long runs of wires to each unit.  A ferrite choke at
each unit might cure it.  You could try the Radio Shack ones or order
them from a dealer listed in QST/CQ.  I wouldn't try adding anything to
the circuitry (like caps) unless the mfr says it's OK to do so.  

Disconnect one unit at a time and check if it stops each time.  Keep
doing this until it stops.  If not, they may all need a choke with as
many turns of wire on them as you can get. Then reverse the process
adding chokes one at a time and testing to make sure it works before
moving on to the next unit. Before spending a lot of money, you should
try one choke with only one unit hooked up and operating to see if it
works.  If so, buy more chokes and install them one at a time.  Some
units might need more turns than others.  I think the right ferrite mtl
to use is either 73 or 77; if wrong, someone on the list will certainly
correct me!  :-)

73, de ed -K0iL

-----Original Message-----
From: rfi-bounces@contesting.com [mailto:rfi-bounces@contesting.com] On
Behalf Of Van Fair
Sent: Saturday, August 21, 2004 12:09 PM
To: rfi@contesting.com
Subject: [RFI] RFI to intercom


My next door neighbor has an houswide intercom system that picks up my
20 meter SSB signal and sends it all over his house to 10 speakers. The
radio in it is turned off but it does have an antenna in the attic. The
unit is supposed to be a high end system by M & S in texas model MC 602.
The unit cant be turned off as it serves as a door bell and has no off
control. I knock him out of bed if I transmit late at night!!! Anyone
have any thoughts on how to handle this problem. Neighbor is 100%
cooperative and knows it is not my fault.  I run 1kw on 20 and it
mailnly affects him when I turn my 4 El Steppir towards his house. My
guess would be that the RF is being picked up on the speaker or AC wires
and brought into the amplifier. What can he or I do to the unit to stop
this from happening.  Thanks Van W4GIW
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