>
>On Tue, 9 Dec 97 18:24:56 -0800 Rich Measures <measures@vc.net> writes:
>>>
>>>On Mon, 8 Dec 97 20:00:24 -0800 Rich Measures <measures@vc.net>
>>writes:
>>>SNIPS
>>>I AM suggesting that 1500W of 28MHz RF from any amp will seriously heat
>>>up a #16 CU wire from the plate cap thru to the top of the Tune cap.
>>>I suspect that you could understand why if you stopped your hyperbole long
>>>enough to study it.
>>>Dick, Tom, Ian and others I believe have covered this ages ago.
>
>>RG58/u is rated at roughly 600w at 28MHz -- which works out to 2.3A.
>
>The actual ratings of RG58A/U is 650W at 10 MHz not 10M. At 50 MHz it is
>250W. But that has nothing to do with the discussion.
>You must have been taking dancing lessons from another.....
>
I did the math.
>
>>As I recall, the center conductor of RG58/u is quite a bit smaller than
>>#16 -- like maybe #19. If 1A will "seriously heat up #16 gauge Cu", why
>>doesn't 2.3A seriously heat up #19 (or so) gauge copper?
>>- At 25A/60Hz, #16 gauge Cu gets seriously warm in free air. Does it make
>>sense that
>> 1A at 28MHz could do essentially the same thing?
>
>
>Why dont you just try it and find out.
> Replace all the plate wiring and
>strap in your SB-220 and key down for several minutes.
>
I don't need to try Cold Fusion to know that it's a delusion.
- 1A at 28Mhz in #16 gauge Cu,, generating serious heat? Give us a break.
And besides that, if Ls was cookin' Rs, it would leave barbeque grill marks on
Rs, which it does not.
,,, ,,,
... ...
>>One SB-220 owner told me that he took the 220 to work and put a probe
>>from a spectrum analyzer through the perforated cover of the output
>>compartment. The signal was 50wpm CW dits. He said he could see the
>>damped-wave ringing at c. 110MHz at the beginning and ending of each
>>dit, and whenever the amp. was keyed or unkeyed with zero signal drive.
>
>And replacing the possibly overheated and overvalue 47 Ohm 2W carbon
>cured it ??
>There should have also been grid current flickering when it was zero
>drive keyed if the parasitic was that pronounced as to always be there.
>It would not suprise me that a slight change in the L spacing on the
>resistor would have altered the analyzer picture. Did your owner take his
>tests thru to a cure or conclusion?
>
No. Damped ringing is not regenerative. Damped ringing will always be there
whenever the anode current changes, no matter how low the VHF-Rp of the
suppressor happens to be. .
>Too bad; but that is still just a minor parasite....
? no parasite, just damped ringing of an L-C resonant circuit.
>I asked about a Big
>Bang analyzer picture. Or do you find those dancing shoes moving again?
One would need a memory-type spectrum analyzer to lay in wait for the Big Bang.
Most stock amplifiers never ever have a big bang.
... ...
>The Big Bang will generate tremendous amounts of RF, at that instant, of
>unknown frequencies. Zeners and the like do not handle that very well.
- The current path from the alleged anode/grid vanishing-gas arc is not
through the bias zener. However, with a parasitic oscillation, the fault
current path would be through the bias zener.
>It
>does not have to be in the direct path if the wiring is saturated with it
>and in the SB-220 at least the Zener protrudes into the RF cavity.
It might be interesting to measure the C between the chassis and the zener
diode stud that protrudes in the RF cavity.
>> The voltage drop across this amount of R would be 2.4v peak -- which
>>equals 0.06w peak in a 100 ohm Rs.
>
>That assumes a DC path only. If the L in the suppressor is acting as a
>RFC then the R takes all the gaff or in actuality the load is somewhat
>shared assuming an imperfect RFC.
This L is only 0.09uH. With a DC pulse?, hardly. With a 110MHz regeneration,
possibly.
cheers
Rich...
R. L. Measures, 805-386-3734, AG6K
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