[Lowfer] wireless doorbells

[Dexter W4DEX]

Douglas D. Williams wrote:
> Well, my (unknown age) doorbell finally bit the dust. It's the old wired
> style with the bell in the hallway and the transformer in the attic. I may
> just replace it with one of the newer wireless models. I assume they operate
> on a Part 15 frequency. Anyone know if I am apt to experience any QRM issues
> on LF? Does the button only transmit when pressed?
>
>   
Most of those type license free devices work on UHF so it's very 
unlikely to make any noise on LF.  I saw one type that had two way 
intercom which operated on 900 MHz.  Other common frequencies for 
consumer wireless devices are 315 and 433 MHz.  Yes, right in the 70 CM 
ham band!  If I tune between 433.5 and 434.5 I hear multiple wireless 
thermometers and other devices from miles away.  But that is with a high 
gain antenna and a low noise figure preamp.  Fortunately these devices 
haven't caused me any problem on the primarily weak signal frequency of 
432.100 +/- a hundred kHz or so.

Dex

BTW, I have see very old doorbell transformers generate LF noise.  I 
assume when they start arcing internally.