[RFI] CO Detector

Rick Low n6cy at earthlink.net
Thu Feb 15 19:50:30 EST 2007

Wanted to add some data points to the earlier messages this month on the
I live in a northern Virginia neighborhood where the lots are about 1/4 to
1/3 acre. I have zero RFI to my home electronics and home alarms, but one
neighbor among five has false alarms on his Kidde carbon monoxide
detector(s) when I transmit from my yagi @ 55ft from anything over about 150
watts. This occurs 20 through 10 meters.
Kidde is apparently related to First Alert brand and the NightHawk model.
Inquiry to Kidde resulted in an answer that was reasonable, in my opinion.
For the "ham" side of the equation, check station grounding, harmonics
emission, and RF on the coax shield, including placing ferrite beads on the
AC power lead to the transmitter (ok, transceiver in my case) and on the
transmission line.
For the consumer end, unplug the CO detector and let it operate on battery
to see if the house AC wiring is coupling RF into the detector, and place
ferrite beads on the leads going to the detector if necessary (challenging
since these detectors plug directly into the wall outlet, but the previous
posts on AC line filter might be possible).
The help line did not (I emphasize) admit any statement that their CO
detectors could be susceptible to RF, but the nature of the answers
indicated to me they probably get more than a few inquiries of this nature.
I haven't been completely successful in convincing my neighbor that he needs
to help resolve the RFI, but that's a separate issue!
Rick N6CY Reston VA USA

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