[RFI] Smoke and CO alarms

[Jim Brown]

On Sat, 29 Sep 2007 08:27:03 -0700, Rick D wrote:

>Woke the dogs and XYL setting off my First Alert BATTERY operated 
smoke and CO alarms.

>Any known cure short of QRP or QRT ?

You could always just remove the batteries. :)

Seriously though -- are they completely stand alone, or are they 
wired into anything? If wired, try a capacitor on the order of 
0.05uF across the wires. Also, if wired, replace the wiring with 
twisted pair (like one pair of an Ethernet cable). And, if wired 
into something, perhaps the RFI is triggering it rather than the 
alarms. A serious ferrite choke on the wiring might help. 

If not, poke around inside to figure out the circuit, and try a 
smaller value capacitor (perhaps 100 pF or 470 pF) across whatever 
the sensor is triggering. 

Another question. Are they actually triggering the alarm, or is 
the beeper (what we might generically call a Sonoalert, after one 
of the first major mfrs of them) reproducing your CW? If the 
latter, use the larger capacitor across the beeper. 

For further details, see audiosystemsgroup.com/RFI-Ham.pdf

73,

Jim K9YC