[TenTec] RF gets into computer (ADT Alarm System)

[Ron Castro]

Common mode rejection filtering is generally what fixes these types of 
problems.  The RF is induced to all of the wiring connected to the device, 
then tries to find its way to ground through the power wiring with all the 
control circuitry right in the middle.  You have to break up the path and 
the most painless, non-invasive way is with ferrite torroids.

The 'bible' on how to use these is on this link:

http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf

The large 2.4" units are Amidon FT-240-43 (www.amidoncorp.com) and the 
smaller ones, 1.02" OD, .505" ID 1.125" long work very well (and are much 
cheaper) if you don't have a large connector that has to thread through the 
loop.

I recently fixed a nasty problem with my lawn sprinklers using this 
technique that would cause the solenoid valves to "bang" on and off when I 
talked on 75 meters.  I wrapped all the incoming wires from the solenoids 
around a 2.4" Mix 43 core where they entered the control box, and wrapped 
the power wire that went to the "wall wart" on one of the small cores.

This also fixes problems with stereo systems, telephones, cable TV, garage 
door openers and more!

                     Ron N6IE
                www.N6IE.com



----- Original Message ----- 
From: <W4ABW at aol.com>
To: <geraldj at storm.weather.net>; <tentec at contesting.com>
Sent: Sunday, April 22, 2007 10:00 AM
Subject: Re: [TenTec] RF gets into computer (ADT Alarm System)


>I use the FT-1000MP and I get RF (I think) into the ADT Security alarm
> system. It sets off the alarm when its not armed. Any thought on this? 
> Its  only
> troublesome on 40m where I use a dipole that's closer to the house than my 
> 80m
> dipole and my tri-band beam. My 80m dipole is just a lil farther away and
> has never caused this effect. The  firemen have been out here twice  now.
>
> thanks
> Al
> W4ABW
> Raleigh
>
>
>
> ************************************** See what's free at 
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