I may not have been clear as to what happens when the power supply
rectifiers modulates the RF.
The hum will only be noticed locally where the signals from the power line
are strong. But other stations will not
hear it because the signal they receive is from your antenna and not the
power cords. So it can just be ignored.
73
Bill wa4lav
How are you monitoring the hum when you transmit? Possibly another
receiver in the hamshack?
If you are using another receiver near by it may not be real. Some times
RF gets into the
power supply and the rectifier diodes that are switching on and off at 120
Hz rate amplitude
modulate it and it is re-radiated by the power cords. If this happens the
solution is to ignore it or
put RF bypass capacitors across the rectifiers.
Usually Magnetic field coupling into the transmitter is only noticed when
transmitting phone due to the fact that the microphone preamplifier is
sensitive enough to amplify the small millivolt signal produced by the
magnetic field from the transformer.
73
Bill wa4lav
At 09:49 AM 12/17/2003 -0700, you wrote:
Y'all,
I just became a new owner of an Argonaut 505, the very first Argonaut and
my first Ten Tec rig. It came with the model 210 power supply. I am
noticing a 120 Hz hum on the transmitter note on CW and a corresponding
hum on the SSB signal when I run the rig from the 210. When I power it
from a battery there is no hum. It is most noticable on 40 meters which
is where the local oscillator is tripling, and I don't see a hum on the
wave-envelope with my HP1740A 100 mHz oscilloscope. So it may be FM on
the local oscillator.
I would appreciate first of all a circuit diagram for the 210 power
supply, and then of course any suggestions about what to do. It is a
really fun little rig when I run it from the battery.
Thanks,
Jim Hanlon, W8KGI
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