[RFI] Smoke and CO alarms

[Ed Richardson]

In my case, the antennas were mounted on the roof of our 1 story bungalow. The affected detectors were immediatly below the vertical and the balanced doublet antenna. Separation was 12 feet vertical from the base of the vertical antenna and 30 vertical feet for the feedpoint of the doublet. I used a balun and line isolators on the vertical, along with resonant radials.

False tripping occurred on 80m with about 200 W and on 15m with about 400 W. I could run 800W PEP on the other HF bands without false tripping the detectors.

I am sure separation would help significantly. It just wasn't practicle.

Ed
VE4EAR

----- Original Message -----
From: dgsvetan at rockwellcollins.com
Date: Tuesday, October 2, 2007 2:55 pm
Subject: Re: [RFI] Smoke and CO alarms

> 4.  Ed, it sounds as if you have a fair amount of RF
> coupled onto your
> alarm system wiring.  It's great that you were able to get
> rid of the
> false tripping, but it would be interesting to know the type and
> orientation of the antennas that are producing those fields, as
> well as
> bands and power levels used.  Is there any opportunity to
> relocate the
> antennas?  In difficult situations, if replacing the
> detectors with
> protected types is not an option, consider antenna
> relocation.  If I
> recall correctly, field strength in the near field (typical
> situation for
> 160, 80, and 40 meters) varies inversely as the cube of
> distance.  That
> means that moving the antenna just a little farther away could
> make a lot
> of difference.  In the case of wire antennas, broadside
> versus end also
> makes a difference.
>