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View Full Version : RF sets off First Alert CO alarm



N6RLS
07-10-2011, 10:12 PM
For some reason, if I operate at "too much" power (40 watts or more - in PSK31 mode) the CO alarms in my house start beeping - 3 or 4 beeps... pulling and reinserting the batteries seems to fix this issue.

Anyone else had this problem or ever heard of it? :confused:

The First Alert alarm is Model # CO400

KA5S
07-10-2011, 10:59 PM
Not uncommon. We had a smoke detector at Tandy R&D that called the FD whenever Security checked in from the printer room.

Your antenna roof/attic installed?


Cortland
KA5S

W0SGM
07-11-2011, 12:20 AM
no..but all I have to do is key the mic and the motion light in the yard goes on !!! everytime I key the mic,or tx in anyway,with power out or not,that light goes on.. Still haven't found a fix,

KE3WD
07-11-2011, 12:23 AM
So turn down the RF output, it is, after all, PSK31 - which works wonderfully with 5W output here...


73

N6RLS
07-11-2011, 10:40 AM
Not uncommon. We had a smoke detector at Tandy R&D that called the FD whenever Security checked in from the printer room.

Your antenna roof/attic installed?


Cortland
KA5S



One is outside, the other runs through the house... I tried to recreate the problem by holding the alarm unit next to the indoor antenna - wouldn't set it off... seems to be a certain combination of power and frequency... gotta test more - but everytime it has happened was during a transmission with either the indoor or outdoor dipole, with the power up more than about 40 watts... and yes, it is PSK31, but conditions have been pretty bad lately and so I tried boosting the power a bit and "beep! beep! beep!" there goes the CO Monoxide alarm.

N7SMI
07-11-2011, 02:01 PM
We went on a cruise recently and operated a HT from our cabin. I realized that when I transmitted (even at 1 watt), the emergency, water activated lights on the life jackets in the closet all illuminated. Weird!

AA7EJ
07-11-2011, 02:07 PM
Good indictor of poor ground or bad antenna design!
My wife's document shreader runs wild when I experiment with my latest antenna.

W1GUH
07-11-2011, 02:31 PM
What's really fun is when you try to operate from a hotel room and the RF sets off the building-wide alarm AND the fire department shows up. Oops! :o

No, I DIDN'T tell the firefighters that there's no real emergency, just a "small" RFI situation. QRP only in hotel rooms now.

My biggest fear was that they'd trace it to my room but whew!, didn't happen.

K9STH
07-11-2011, 03:22 PM
EJ:

More likely poor design of the alarm!

It is virtually impossible to stay out of some alarms even when running low power and excellent antennas. Since the vast majority of these alarms are not affected by r.f., the manufacturers do not include any shielding or other r.f. prevention circuitry. "Touch" lamps are another product that it is very difficult to keep from being affected by r.f.

Many systems installed by alarm companies have problems with r.f. Those companies are aware, at least at the corporate level, and do have components available to prevent r.f. from activating the system. Unfortunately, many technicians at the local level don't have a clue as to what the problem involves and will try to blame the transmitter.

Glen, K9STH

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