Fwd: Re: [TenTec] Argonaut 505

[Bill Fuqua]

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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>>TenTec at contesting.com
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