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
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