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Re: [RFI] RFI With Smoke Detectors

To: rfi@contesting.com
Subject: Re: [RFI] RFI With Smoke Detectors
From: Stan Zawrotny <k4sbz.stan@gmail.com>
Date: Wed, 19 Aug 2015 15:29:49 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>

>>Does the interference to the smoke detectors occur at very low RF
>>output...say 5 or 10 watts?  Or does it occur only AT higher output levels.

It increases with power. Gets really bad when I kick in the linear.

>>Can you get schematics for the smoke detectors?

No. Only whats available on the internet.

>>Have you attempted to contact the importer or manufacturer to inquire about
>>the application of bypass caps to AC power lines or battery leads as well
>>as other parts of the device to minimize the effect of RF on the chirp

An email to the manufacturer, USI Electric Inc., went unanswered.

>>In the short term, disabling the offending devices except when testing is
>>one way to cope. Battery operated spares can be temporarily placed while
>>you sort thus out.

When I disabled the nearest one (in the office/shack) the one in the
foyer chirps. When I disable that one, the next nearest one chirps. I
disabled them by unplugging them completely. It is a two-family house
that I built with my daughter and her husband, with us having the
in-law side. There are a total of 22 alarms.

>>What sort of antennas are you using and how high are they?

My antenna is an 80-6 meter OCF up about 40 feet in the trees. I don't
think it is radiating back into the house. The house is ICF
construction with a tin roof. I essentially live in a Faraday cage. I
have to go outside to use my cell phone. The house will withstand a
cat 5 hurricane or tornado.


Frank N. Haas KB4T
Utility Interference Investigator
ARRL Tech Specialist, RFI, N FL Section

Stan Zawrotny, K4SBZ
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