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Hi Gary,
reminds me of those pretty little asterisk- or
spider-shaped artifacts which occasionally appeared on MF and were
discussed on this list a couple of years ago. I think the most plausible
explanation we found was the acceleration of a brushless synchronous motor.
The chopper fundamental frequency might be generated by a digital PWM
controller having a stable crystal clock, and the variable sidebands
are due to the rotor angle rate dependent modulation.
Perhaps this one is similar? Maybe a modern
laundry machine or dishwasher coming up to speed, overshooting a while, and
then settling on the preset rpm rate.
Best 73,
Markus (DF6NM)
----- Original Message -----
Sent: Tuesday, January 08, 2013 8:26 PM
Subject: LF: Strange signal
Hi All,
I am seeing a strange signal centered on
474.750 kHz. It is periodically visible & audible on my grabber system
& my JRC NRD-345. there appears to be no data, just continuous tones. Both
systems using separate antennas.
I have placed a capture on Dropbox of the grabber
image & you can see the end of a previous period & the start of a new
one. The signal pattern starts with a bulge at the beginning but just shuts off
at the end.
I have also placed a capture from the JRC Rx with
SpecLab running at QRS01.
Any ideas or knowledge of this signal
?
73,
Gary - G4WGT.
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