>measures wrote:
>>
>> >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. .
>>
>
>These are 1-inch diameter globars and two are paralleled, so I believe
>the inductance would be considerably less, and that inductance is
>swamped by parallel resistance. (It did work wonders!)
>
Agreed, , Dan. However, for the optimal suppressor -- to maximize
stagger-tuning -- the L-supp needs much more L than R-supp. //
According to Terman's ''Radio Handbook'', doubling the width of a
conductor makes for little decrease in L. My guess is that the ideal
R-supp would be a wide, hollow disc.
cheers.
- Rich..., 805.386.3734, www.vcnet.com/measures.
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