>
>Sorry, but OE is doing it usual job on attribution. I hope I've made the
>sequence of comments clear.
>-----Original Message-----
>From: measures <2@vc.net>
>To: Steve Thompson <rfamps@ic24.net>; AMPS <amps@contesting.com>
To: <amps@contesting.com>
>Date: 06 August 2000 19:14
>Subject: Re: [AMPS] Suppressors
>
>
>
>>>This is not the case. To optimize the staggered resonances effect, one
>>>needs equal VHF current in Rsupp and Lsupp.
>>>In other words -- An optimal suppressor divides the anode-resonance
>>>ringing current between L-supp and R-supp.
>>
>>Why is it necessary to aim for this specific 'optimum' circumstance.
>
>Because the staggared-resonances are optimal when there are equal
>currents through R-supp and L-supp at the VHF anode-resonance freq.
>
>--------------
>I can only guess at what you are visualising when you refer to 'staggered
>resonances'. It would be interesting to do or see some analysis that shows
>the optimisation.
? A parasitic suppressor has two current paths whose EMFs are decoupled.
Thus, the higher inductance path (L-supp) resonates the anode a bit
lower in freq. than does R-supp. The effect is similar to stagger-tuning
an IF transformer to reduce Q/increase bandwidth. .
>
>If the current split between resistance and inductance is equal, then Q=1.
>Lower Q means more current in the resistor and less in the inductor - is
>this better because it's lower, or worse because it's not 1?
>
As I see it, the currents should be equal for maximal stagger tuning
effect.
>>There are two requirements - one is to insert enough resistance to kill any
>VHF
>>resonance that might cause oscillation,
>
> The resonance can not be killed. It can only be damped with
>resistance.
>-------------
>
>Fair comment - sloppy use of language on my part.
>
>
>>the other is to insert sufficiently
>>little resistance at the operating frequencies. Any given collection of
>>components and layout will have its own particular optimum suppressor
>>values, and sometimes nichrome will achieve this better than copper.
>>
>If one wants to reduce 10m dissipation in R-supp and lower VHF-Q roughly
>50%, nichrome is a sound engineering choice. .
>
>---------------
>I'm not arguing that it isn't.
>
>>The important point is the VHF Q of the whole anode circuit, and that is
>>controlled by the ESR of the suppressor, not the Q of the suppressor.
>
>? On Wes' chart, please see column Rp. VHF amplification is
>proportional to the total Rp between the anode and the Tune-C.
>
>Isn't it Rs rather than Rp that counts in a series circuit?
>
Parallel equivalent resistance works a bit more familiarly with the
voltage gain equation. However, the series equivalent (R) or parallel
equivalent (S) predict = gain.
>>At 100MHz, Rp in the copper-wire suppressor, was 166-ohms. In the
>resistance-wire suppressor, it was 101.7-ohms. . Similarly, VHF Q at
>100MHz was 2.2 for the copper-wire suppressor and 1.5 for the
>resistance-wire suppressor. The bottom-line is that (VHF) ESR, Q , and
>Rp are mathematically linked.
>
>
>Agreed - it's a matter of which of them is important.
>
If you are trying to build a VHF oscillator, high VHF Q is better. If
the three are linked, one is not independent.
>
>There is a troublesome VHF resonance in an amplifier and I have two
>suppressors. Measuring their series equivalent values at the troublesome
>frequency, one inserts 30nH and 10 ohms resistance, the other inserts 50nH
>and 15 ohms resistance. Which one will dampen the resonance more?
>
There are four resonances.
later, Steve
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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