>Hi Bill,
>
>> I think I see a basic error in the above. The R introduced by the
>> nichrome-wire suppressor isn't Rp, it's Rs - so it's in series with
>> the suppressor inductance, not in parallel. Right?
>>
>> 73, Bill W7TI
Right.
The nichrome wire's built-in series-R was but a few ohms at 100MHz.
However, these few ohms decreased the parallel-equivalent R (Rp) of a
3-500Z's VHF suppressor from 166 ohms to 101 ohms.
>Hi Bill,
>
>No, that's not exactly correct. Let me take a stab at "un-confusing"
>this issue.
So now there's an "exactly correct" in addition to plain old-fashioned
correct. I'm confused already.
...snip...
>We all know adding turns to the suppressor makes most PA's more
>stable at VHF.
--true
>The bigger the coil, the better the stability but
>the bigger the resistor also has to be. A bigger suppressor has
>higher Rp.
'Bigger' has nothing to do with Rp. There are four determiners in
arriving at Rp.
1. The resistance of Rs.
2. The series-inductance in Rs (9nH in the resistors used in our
suppressor retrofit kits)
3. The inductance of Ls.
4. The series-resistance in Ls. (the difference between traditional
suppressors and R-wire suppressors)
>The reason a higher Rp value in series with the anode DECREASES VHF
>gain more than lower Rp value is simple to explain. ........
Bzzzzzzzzzzzzzzzzzt. (cough, cough)
Mr. Rauch is essentially saying that voltage amplification is equal to
Mu*(1/Rp). However, the second term in the accepted formula is NOT a
reciprocal---i.e., the accepted formula is: Mu*Rp.
...snip...
>Series resistive losses (such as winding the coil from a lossy
>material) in the coil have greater effect as the frequency is
>lowered, ...
Lowered?.........According to Wes' measurements, the nicrome-60
(NI-Cr-Fe) coil exhibited 0.47 ohms of ESR at 10MHz and 4.7 ohms of ESR
at 200MHz. If what Mr. Rauch says is true, silver plating has a greater
effect at low frequencies. If what Mr. Rauch says is true, UHF cavities
should be surfaced with nichrome foil.
...snip...
>If we add a suppressor with too much Rp, it might get too hot on ten
>or 15 meters.
The W8JI suppressor exhibitited about 2/3 more Rp than the AG6K
suppressor. Does this mean that the W8JI suppressor might get too hot on
10m or 15m?
>This stuff really isn't that complex, it's just no one has ever
>written anything detailed in amateur publications.
Hmmm. That statement explains a Great deal. Reid Brandon said there
were no articles in QST on vhf suppression. Amazing.
>The lack of articles is probably why engineers (like Ian, N7WS Wes,
>Gary Coffman, and so on), who learn this stuff formally and use it
>every day, often get perplexed or irritated when someone
>appears to "twist it all up".
Mr. Rauch: In your opinion, would inverting a term in an established
formula qualifiy as twisting?
Neither Messrs. Coffman, Rauch, Stewart, or White has so far delivered
on the Ls/Rs values for a conventional VHF suppressor that would produce
a lower VHF-Rp than the resistance-wire VHF suppressor. And why not?
Are they perhaps perplexed by a certain uneasy feeling that they just
might be walking into an ambush?
Rich---
R. L. Measures, 805-386-3734, AG6K
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