[RFI] RFI With Smoke Detectors

[Stan Zawrotny]

I have an RFI problem with my smoke detectors. The house has USI Electric
Inc. Model USI 1208 smoke detectors installed throughout. Mostly when I
operate on 40 meters, but also on 80, 15 and occasionally on 20 (not
often), the smoke detector in my office where my FTdx5000 is located will
chirp intermittently. It doesn’t start right away and will sometimes pause
for long periods of time.



433.93 MHz is one frequency used by smoke detectors. It is the 60th
harmonic of 7.232 MHz, a 40 M SSB frequency. The chirping will occur when I
am operating as low as the RTTY band (7.025 – 7.125).



I have tried installing toroids from a Polomar “RFI kit” without luck. I
also installed an MFJ-704 low-pass filter in the antenna line, also with no
results.



I disconnected the smoke detector in my office and the smoke detector in
the foyer began to chirp. Because they are RF connected, another one in a
distant part of the house also chirps.



I suspect that the close proximity of the rig to the smoke detectors just
overpowers the toroids and that enough RF gets out from the transmitter and
the short coax to negate the effectiveness of the low-pass filter.



Is there anything else that I can do so that I can operate on 40 meters
without upsetting the family?
___________________
Stan Zawrotny, K4SBZ
K4SBZ.Stan at Gmail.com