>
>Are you guys playing Rich's word games again?
>
>Wes, the person who made the measurements, concluded there
>was no advantage to using nichrome. Rich, despite making an
>agreement to not "cook" Wes' data, did exactly that.
>
>Rich re-worded things.
>
Rich did not change any measurement.
>> Rich says:
>>
>> > Rp was 101-ohms for a resistance-wire suppresor vs. 166-ohms for a
>> >copper-wire suppressor.
>>
>> Something puzzles me here. If the suppressor provided the whole plate
>> load impedance at the parasitic frequency, then the gain would be
>> reduced by only 4.3dB by lowering the parallel resistance from 160 to
>> 101 ohms. This may be enough to just stop the parasitic, but doesn't
>> appear to my mind to give enough margin to ensure stability.
>
>A lot of things should puzzle you Peter:
>
>1.) The frequency Rich selected is LOWER than the frequency
>where the amplifier actually would oscillate.
Wes choose 100MHz. This is close to where parasites typically occur.
>This makes the
>difference larger than it really is, since Rich's suppressors lower
>the Q most at low frequencies.
>
>2.) The suppressor Wes tested was NOT the hairpin Rich
>recommends, it was a larger inductor made exactly the same as
>the stock suppressor except with nichrome. If you actually use
>Rich's hairpin, VHF Q actually INCREASES over the stock
>suppressor when the whole system is considered.
>
100nH with a coil-inductor is the same as 100nH with a U-inductor.
>> But in reality, the suppressor is only part of the plate load
>> impedance. As a result, the change (percentage reduction) in the load
>> that the plate sees is even smaller, so the gain margin between
>> oscillation and stable operation becomes even less.
>
>Bingo. You won't find that on Rich's web page.
>
>The entire thing is nonsense. I measured the VHF anode Q of a
>amplifier with a pair of 3CX800's with a stock suppressor, and again
>with Rich's nichrome. The VHF Q increased when the Measure's
>suppressor was used.
. Resistance wire produces a higher Q than copper or silver?
>
>That's because Rich's suppressor has less Rp, and when that Rp
>is placed in series
the "p" in Rp stands for parallel.
> ...with anode lead the reactance of the anode lead
>dominates the system.
>
jabberwocky
>Rich focuses on Rp because he can make a pathological argument
>that "less Rp is better".
>
is less VHF gain is better?
>Of course anyone who understands the system also knows the
>exact opposite is true. When a lower Rp is inserted in series with a
>fixed reactance, system Q increases.
>
welcome to the Rauchian world.
>........
- 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
|