[RFI] M&S Systems intercom RFI where to start

Rob Atkinson, K5UJ k5uj@hotmail.com
Mon, 03 Jun 2002 21:59:15 +0000

Perhaps you should try wrapping the wires going in and out of each intercom 
unit around ferrite beads (chokes)?  I assume the communication wires are 
thin so you could wrap many turns around each bead.  If the wires are 
already going somewhere you will have to wrap the slack around a split bead 
(since you can't disconnect the wire).  Palomar Engineers sells ferrite 
beads.  RF Parts is another source.  I like the RF Parts split beads and the 
Palomar rings.   I think the addresses are www.palomarengineers.com and 
www.rfparts.com.  These get rid of (or attenuate) rf travelling on the audio 
wires and also ac lines gg into the units.  Of course if something is 
rectifying your sig. inside the intercoms these won't help.

You don't say if you are interferring with things in your own home.  If you 
are, then you may have to solve some station problems.  You may need a balun 
at your feedpoint, a common mode filter and low pass filter at your linear; 
you may need to get rid of some ground loops and improve your shack ground 
or run the linear into a transmatch (even if you don't need it, it's an 
extra tank circuit that will attenuate harmonics below the cutoff on the low 
pass filter).


Rob Atkinson

----Original Message Follows----
From: "kb4tcu" <kb4tcu@accessatc.net>
Reply-To: "kb4tcu" <kb4tcu@accessatc.net>
To: <rfi@contesting.com>
Subject: [RFI] M&S Systems intercom RFI where to start
Date: Fri, 31 May 2002 01:30:07 -0400

Seeking Help,
  I recently got my station on the Air. After a few nights of operating on 
the 75 meter band with output around 900watts. My next-door neighbor 
informed me I was causing interferance to his M&S systems model 602 

http://www.mssystems.com/downloads.cfm?file=115755d.pdf     install diagram 
for the offending unit MC 602

  He is not argumentative.My neighbor, while allowing me to to try to 
alleviate the problem, He is the curious type. I would like to make some 
progress on my first attempts. Today I hooked up my Uhf remote link to Hf 
allowing me to transmit inside my neighbors home. The audio from the 
interferance my station is causing is showing up on all stations. The audio 
level is very low. My neighbor listens to the intercom in his bedroom in the 
monitor mode. This allows him to listen to his son's room across the house. 
As he prepares for sleep his room becomes very quiet and thus (my distorted 
audio becomes audible on his room intercom station).
  He is going to allow me to install some bypass caps and or rf chokes.

  My station consistis of a icom 746 within alc driving a Ameritron AL 80A 
feeding RG8U to a 1/2wave inverted V at 40' to the apex. The antenna has a 
very good VSWR
and is 50' from the nearest componet in His intercom system. The antenna is 
broadside to his home .

Need help

Victor Vickers KB4TCU

--- StripMime Report -- processed MIME parts ---
   text/plain (text body -- kept)
RFI mailing list

Join the world’s largest e-mail service with MSN Hotmail.