Bill,
Thanks for the input. I am monitoring with another receiver in the shack and
with the Argonaut driving a Heathkit Cantenna. I can hear an obvious
difference when I change the power supplies, the 210 and another regulated AC
supply produce a hummy cw note while my battery supply is clean. I have also
gotten an over-the-air report on the hum, so it is real.
Jim
----- Original Message -----
From: Bill Fuqua
To: tentec@contesting.com
Sent: Wednesday, December 17, 2003 12:20 PM
Subject: Re: [TenTec] Argonaut 505
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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>TenTec@contesting.com
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