[TenTec] Argonaut 505

[JAMES T HANLON]

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 at 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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