[160m] Birdie

[Tom Rauch]

In the past most used to be from TV sets. TV birdies from the 
sweep system in TV sets occur at multiples of just under 16kHz, 
because the sweep system operates at around that frequency. 

The dominant sources now are the small switching power supplies 
in everything from TV sets VCR's and computers to battery 
eliminators and chargers. My Cannon Fax machine is readable at 
about 500 feet, and an Igloo 12 volt refrigerated cooler I have is very 
very nasty at a much larger distance.

I used to hear the switching supply in a neighbor's computer quite 
well, and they live over a mile from me. I gave them a RF-bypassed 
lightning arrestor outlet strip that also connects to their modem line 
to keep the RFI out of the phone line and power lines. 

Switching supplies can cause QRM even when the device is turned 
off, as long as they are connected to the power line. They run on 
random frequencies usually above 25 kHz, so harmonics are 
25kHz or more apart.
73, Tom W8JI
W8JI@contesting.com