>
>> >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.
>
>Staggered resonances?
>
Not that kind of staggering, Tom.
>The only resonance important to "stagger" for stability is the
>parallel resonant frequency of the grid and the parallel resonant
>frequency of the anode.
>
In the TL-922, the grid is resonant at roughly 88MHz. The anode is
resonant c. 120MHz. IMO, the 922 is not very stable.
>> If one wants to reduce 10m dissipation in R-supp and lower VHF-Q roughly
>> 50%, nichrome is a sound engineering choice. .
>
>Suppressor Q is a tiny fraction of the anode system's impedance.
Are you talking about the fundamental freq. or the anode-resonance freq.?
>If you look at VHF amplifiers, they have extreme values of VHF Q yet
>are almost always perfectly stable.
>
? HF amplifiers are clearly the squirreliest.
>It's important the anode impedance be a value that produces very
>little gain or the phase shift is such that the amplifier does not
>become an oscillator at the frequency of instability, where the grid
>is no longer an effective shield.
>
>There are dozens of ways of accomplishing that.
>
Please name two.
thanks
>Nichrome simply adds series-resistance in the primary path of low-
>frequency currents. It offers the largest change in loss in the
>suppressor at DC, and the least change at the highest frequencies.
>
Been there. Done that. Please see Wes' measurements.
>Nichrome is a good choice when the PA has instability near the
>operating frequency, and you don't want to correct the design flaws
>making the PA unstable near the operating frequency.
>
For larger blooms, spread around rose bushes after pruning.
>The biggest flaw in the after-market suppressors sold is they have
>low values of series inductance, making VHF Q higher than a
>conventional suppressor with more inductance and a modest value
>of shunt R in some systems.
>
In Wes' measurements the resistance-wire suppressor had a Q of 1.5 at
100MHz. The conventonal suppressor (W8JI) had a Q of 2.2. Why was this,
Mr. Rauch?
>I have to chuckle when low Q HF nichrome suppressors
? Whasup with that.? The copper-wire suppressor had a Q of 19.7 at
10MHz and the resistance-wire suppressor had a Q of 7.6 at 10MHz. It is
almost as if Mr. Rauch does not see these numbers. The long trip on the
wide river in the Land of the Pharoahs continues.
>are installed, and people talk about how "smooth" the amplifier then
>tune on ten meters. Of course they do, the tank system unloaded
>Q at 28 MHz has been noticeably lowered!
>
[chortle] Our customers report no measurable difference in P out on 10m.
Have you measured less output on 10m, Mr. Rauch. With a SB-220, the
most noticible improvement in smoothness is usually on 40m. What do
two dips in anode current on the same band suggest?
>
later, Tom
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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