[RFI] Strange birdies on 10M

[Jim Brown]

I missed Pete's post the first time around, but yes, birdies spaced at 
intervals of 10-40 kHz are created by switch-mode power supplies and 
power control electronics, like controllers for variable speed motors. 
Variable speed motors are used in everything from appliances to HVAC 
systems to elevators to industrial machinery.

The frequency ranges at which they bother us depend on variables like 
circuit design, device construction, and the wiring connected to them 
that can act as antennas to radiate the noise.

These links shows how to identify sources by generic type, and provides 
lots of advice about how to chase them down and kill them.

http://k9yc.com/KillingReceiveNoise.pdf
http://k9yc.com/KillingRXNoiseVisalia.pdf

73, Jim K9YC

On 7/15/2022 10:33 PM, Mike Fatchett W0MU wrote:
> Are they always there?  Our washing machine generates a bunch of similar 
> stuff when washing.
> 
> W0MU
> 
> On 7/12/2022 7:52 AM, Pete Smith N4ZR wrote:
>> Recently (just the last couple of days), I have noticed that my RBN 
>> receiver is showing a far above-average number of decoders on 10M. 
>> Investigating this, I see that *only* on 10M, I seem to have a series 
>> of birdies.  They are every 8 KHz, and are comprised of a central 
>> signal and two weaker ones about 600 Hz either side, and vary 
>> substantially in "loudness", although the loudest are still below S0 
>> on my K3,
>>
>> I'm unlikely to invest much time, considering the weakness of the 
>> signals, but am wondering if the characteristics suggest some 
>> particular kind of SPS or other device