[Elecraft] K2/100 #4198 PA Stability Problem?

Tue May 4 22:39:00 2004

Hi

Did you mount RFC10 down as close to the circuit board as possible and =
against the back panel. It should be setting on the diodes on the board. =
Also does the KPA100 have the shield mod that adds the ground clips if =
not you need to add the new shield and the solder lugs that go from the =
antenna socket to the shield.

Don Brown

  ----- Original Message -----=20
  From: Andy Cook, G4PIQ<mailto:[email protected]>=20
  To: [email protected]<mailto:[email protected]>=20
  Sent: Tuesday, May 04, 2004 7:37 PM
  Subject: [Elecraft] K2/100 #4198 PA Stability Problem?

  Was feeling very smug with myself yesterday having finished the K2/100
  in decent time, but having put it on air in a local contest last night
  and getting some grim audio reports, I've found that I have a problem!
  Since adding the PA, above around 40W on 80m (and maybe just a hint on
  160) I get rough AM on the carrier (spreads a long way - probably =
pulsed
  if I looked on a scope) at a few hundred Hz. Exact frequency rises a
  little with frequency . Sound like LF instability in the PA. On SSB
  makes the audio quite rough - on CW spreads with these sidebands.=20
  =20
  Before I go round applying the usual tricks of extra C and snubbing R
  here and there, any suggestions? Have checked for obviously bad =
grounds,
  wrong components, removing shield, increasing R98 on RF board, extra
  1000uF C from Z1 to ground, but none have a significant impact. Any
  leads?
  =20
  73,

  Andy, G4PIQ

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