[AMPS] Re: Nichrome Wire for Parasitic Suppressors

[measures]

>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.  


--
FAQ on WWW:               http://www.contesting.com/ampsfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm