>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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