>
>Hello Phil,
> This is my first time to write to you directly but I read this e-mail
>with some interest and after a night of thinking about it I had too many
>questions to ask.
>Lets start with something that made me ask HUH?
>> > People really get far too carried away with Q, because efficiency
>> > changes very little with Q as long as tank losses are low. Factually
>> > the lower the loaded or operating Q becomes, the higher the
>> > efficiency becomes until Q is the square root of the impedance
>> > ratios plus a tiny bit. When loaded Q drops below that value,
>> > network phase shift is 90 degrees or less and the network no
>> > longer behaves like a Pi Network.
>
> OK so far. Not being an engineer I have to accept it as fact and I have
>no problem there.
>
>> This is easily observed when one has the luxury of a roller inductor
>> in the tank circuit. If you are looking for a big peak when the Q is set
>> to 12, you are in for a disappointment. Makes more sense to tune for
>> "max. clean" on the 'scope.
>
> OK now I am a bit confused. What does max clean on the scope mean in
>this case? Are we talking about a spectrum analyzer? What?
> In the past few amps that I built, (pair of 813's in GG/ 6 sweep tubes
>in GG/ 10ea. 1625's in parallel GG) all I did was use a small pi matching
>network or some type of input tuning system (tube exciter days) and move the
>tap on the output tank around a bit while tuning up into a dummy load in the
>middle of the band while noticing the output power with drive and the
>position of the tune C. More tune C meant a higher Q as it also coincided
>with less L. The position of the tap was moved back and forth across a
>range until the power output dropped off on either end of the coil tap
>setting with the same input power and drive. The center position of the two
>extremes was where things got hard wired and we went on our merry way. I
>have no idea what the Q was but I did see a place where things did sort of
>peak, or perhaps I should say where they didn't fall off. If I read you
>correctly, you say that isn't the case. If that is so, then how do you tune
>up an amp with a roller inductor? What am I missing here? Enlighten me,
>please?
Set L for the desired Q at the operating f. (requires calculation)
With max. drive, adjust C-tune and C-load for max. P-out. Do not adjust
L.
>
cheers, Mike
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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