Re: Current Draw & Power Output Question

Timothy Fidler

Russ et AL , these are the Bias instructions  straight from the  ubitx website.

It would seem to me that the unit went in the box without bias being done.   Rebias (not sure about the Re.. it may never have been done ??) is at his own risk. It seems to be a ticklish operation as the bias limit resistors are a SNAFU it seems. They appear to have been specified on basis of what the 5V reggy could supply with the potentiometers bottomed out  and not on basis of keeping bias volts in a reasonable range.  The current the chap is quoting is so low cw the below that he might like to check his DVM is in fact in spec...OTOH.....

  • Switch off the rig
  • Locate the two PA bias presets (the blue square ones)
  • Set both the presets  to fully clockwise position, gently.
  • Attach a dummy load or a low SWR antenna and switch the rig on
  • Attach a current meter to the power supply so can monitor the current draw
  • Switch on
  • Press the PTT without speaking ( no modulation)
  • The current draw should be between 470 mA and 500 mA
  • Slowly increase one of the two presets until the current increases to by 100 ma
  • Do the same for the other preset (the total current should have increased by 200 ma now)

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