[AMPS] Re: Nichrome Wire for Parasitic Suppressors

measures measures@vcnet.com
Tue, 8 Feb 2000 13:36:16 -0700


>Hello Rich,
>
>I'm not a member of the Amps Reflector, but I do read the mail there.
>
>Though this may not apply directly to your discussions, I thought that
>you might find it to be of interest.
>
>I work with shortwave broadcast transmitters of 50 and 100 kilowatts
>power output.  Because of the large size of the tubes and the tuned
>circuit components, connecting leads can become quite long and an
>important part of parasitic resonant circuits.  By using lossy
>(stainless steel or Nichrome) materials in these connecting leads, a
>number of instabilities have been solved by damping the Q of the
>parasitic resonant circuit.  Or, in another related approach, take the
>case of the connecting strap from the PA Plate RF choke to the anode of
>the PA tube in a 100kw transmitter.  This is about a foot long.  By
>strapping two paralled high-power glo-bar resistors across this strap, a
>spurious oscillation in the 200 MHz range was eliminated.  'Course, you
>got to be careful where you put the lossy material at this power level,
>or you will make toast! 
>
>I realize that this is not a case of discrete parasitic suppressors such
>as is under discussion.  But I thought it close enough that you might
>find it interesting.
>
Interesting, Dan. I will share this info with the AMPS group.   I used 
the same technique, without the globars,  in the 8169 Ugly amplifier that 
is on my Web site.   The trouble with globars is that they have as much L 
as the strap they parallel unless the strap is  lengthened between the 
connections to the resistor.  .  

cheers.  
>
>


-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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