[CQ-Contest] Re: Bandpass filters, front end protection

[Marijan Miletic, S56A]

All you need to reduce input drive power requirements for SB-220 is a short
piece of wire to connect grids directly to the ground improving the
amplifier operational stability at the same time!

Very good Pi type input filters on SB-220 may require some tuning after that
in order to achieve perfect 1:1 input SWR.

The best bandpass filter article was written by OM Tom, DL7AV in the very
first issue of CQ-Contest journal.  L/C circuits have better Q then coaxial
cables.

73 de Mario, S56A, N1YU, proud owner of SB-220 with original PSU
unfortunately limiting output power to 1 kW.
  ----- Original Message -----
  From: dennis o'connor
  To: n4zr
  Cc: cq-contest
  Sent: Friday, November 09, 2001 6:23 PM
  Subject: Re: [CQ-Contest] Re: Bandpass filters, front end protection



   A friend did an upgrade on his 220 with an outboard power supply, better
   fans, etc... It was a killer amp at 1500W out, all day key down, and he
  used it for several years very effectively before going to a bigger amp..
  .
  I remember my 220 of some 20 or more years ago as having poor input
circuitry...

  Denny
  Nah, just a lousy input circuit SWR, which I need to attack one of these
  days..  I know I could get more out at higher plate voltage, but then
other
  things in the design start to go.


  73, Pete N4ZR
  www.qsl.net/n4zr


  


--
CQ-Contest on WWW: http://lists.contesting.com/_cq-contest/
Administrative requests: cq-contest-REQUEST at contesting.com