>
>
>-----Original Message-----
>From: measures <2@vc.net>
>To: Steve Thompson <rfamps@ic24.net>; AMPS <amps@contesting.com>
To: <amps@contesting.com>
>Date: 05 August 2000 13:48
>Subject: Re: [AMPS] Suppressors
>snip
>>>According to Wes' measurements, the suppressor contributes many 10s nH
>into
>>>the circuit.
>>>
>>The resistor has about 10nH. L-supp is in parallel with it. Total L
>>can not be more than 10nH.
>
>
>Where does the 50-100nH that Wes measured come from?
>
>snip
>
>>>That's not to say that the inductor value in the suppressor
>>>isn't important - you have to choose R and L values to give the ESR vs
>>>frequency characteristic that you need.
>>>
>>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.
>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.
>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. .
>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. 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.
cheers, Steve
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|