On 12/26/2013 6:22 AM, Shoppa, Tim wrote:
If anyone has any insight for how 120Hz impulse noise can just disappear below
a certain frequency, that might help me find it.
Several logical reasons that can happen. 1) The antenna radiating it is
more effective at higher frequencies. 2) The directivity of your RX
antennas with respect to the source is such that they reject the noise
on those lower bands. 3) It's not broadband, because it's electronically
generated. This is true of virtually all switching power supplies, and
many electronic sources. The noise from my SteppIR controller and its
switching PSU wipe out some bands and not others. The PSU is worst on
12M, bad on the bands around it, but not so bad lower in frequency. Now
that I've replaced it with a linear supply, I hear the controller on
the160M that's 25 ft away, so I have to turn it off when I want to work
160M. 4) The source you're hearing on 40M might not have been active
when you were on 160 last night.
73, Jim K9YC
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