[ARC5] AM modulating an "ARC-5" transmitter...

[Leslie Smith]

   Robert (and others)
   I distrust this circuit.  I suspect the circuit was never built and
   tested.
  Does any-one here know of this circuit being used - either on a
  test-bench or actually on-air?

  The circuit lacks stability for the DC bias (operating) point.  If
  used with a battery the operating point will drift as the battery
  voltage drops.
  The result?  Either a low degree of modulation or splatter.

  The claim that the circuit will operate with a crystal microphone
  seems to be unfounded - only Q4 supplies voltage gain;  Q1 to 3 supply
  only current gain.
  The operating bias for the 1625 will be somewhere between -35 and -65
  volts.  If this modulator is to work it will need to supply a peak to
  peak signal AT LEAST 50% of that range. 
   Without the benefit of "spice", - just looking at the circuit I would
   say, "No way."   

  That's my assessment  

  73 de Les Smith
  vk2bcu at operamail.com


On Mon, Oct 12, 2015, at 08:13, Robert  Eleazer wrote:
> As for the transistors for the Simple Modulator, I would use 2N3394 for
> Q1-2-3 (I have a bag of about 100 of them) and a 2N3055 or the TO-220
> equivalent for Q4 (overkill).
> 
> How does that sound?
> 
> Wayne 
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