[AMPS] parasitic suppressors

[Rich Measures]

>
>> Rich said yesterday:
>> 
>> > The Q of resistance-wire falls with increasing f.  
>> 
>> Today he says (In answer to:
>> 
>> >I still don't see any answer as to why the Q of a resistance wire
>> inductor
>> >should actually be less as frequency increases than a parallel R-L
>> >combination) 
>> 
>> ?  It isn't. 
>> 
>> I'm confused. Does the Q fall with increasing frequency for the resistance
>> wire suppressor? If so, why, since theory says it should increase tha
>> ratio of delta.F/sq. rt. delta. F?
>> 
>> >In a typical parasite suppressor, roughly equal vhf currents flow through
>> 
>> >R-sup and L-sup.   
>> 
>> Why? If the tube is not oscillating at VHF, where do these VHF currents
>> come from? 

€  From the same place that RF comes from in a spark transmitter -- from 
a tuned circuit through which DC current pulses are passing.  In an 
apparently stable HF transmitter, whenever current pulses are passing 
through the vhf resonant anode circuit, corresponding damped wave bursts 
of RF at the anode resonance can be observed on a spectrum analyzer.  

>> If it is, then the parasitic suppressor isn't working, and why
>> should the currents then be equal?
>> 
>> 
>	>Parallel R-L circuits are said to have an admittance. Series R-L
>circuits 
>	>are said to have an impedance.  
>
>	That's a convention for making the maths easy. You can deal with
>either as the other using the principles of duality; impedance may well be
>easier for some people (like me) to visualise, rather than calculate.
>Admittance is only the reciprocal of impedance.

€  however, a simple reciprocal it is clearly not.  
>
>	Yesterday, Rich said that the measurements on the copper wire
>suppressor were:
>
>> At 100MHz, the copper-wire suppressor Wes measured an Rp of 166 ohms >(and
>> Q = 2.2), while the resistance-wire suppressor had an Rp of101 ohms >(and Q
>> =1.5).  Sure, resistance-wire does not offer a spectacular improvement over
>> copper and silver wire suppressors, but 40% is nothing to sneeze at.  
>
>However,  I asked
>
>>>In these measurements of suppressors, what was the value of the shunting 
resistance? 
>
>>?  100 ohms.
>
>That must be an awful 100 ohm resistor that put in a parallel with an
>inductor gave a parallel resistance of 166 ohms. 

€   Parallel-equivalent resistance is not "a parallel resistance".  (see 
March 1989 *QST*, pp.25-8)
>........


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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