>
>
>On Wed, 4 Aug 1999 04:39:07 -0700 Rich Measures <measures@vc.net> writes:
>
>>Ä RL = 2000 ohms. R out equals 50-ohms. Freq = 7.00MHz. Q = 10
>>Therefore, C1 = 2000 ohms/10 = 200 ohms. From calculation, C1 = 114pF,
>>C2 = 562pF, L = 5.06uH. Since C1 is effectively in series with C2,
>>C-net = 94.8pF. The resonant freq. of 5.06uH in parallel with 94.8pF is
>
>>7.266MHz.
>>
>>- cheers, Tom
>>
>
>Hi Rich,
> You didn't detail the formulas you used for L & C2 but, from your C1
>calculation, I note that you are using the classic "time-dishonored"
>approximation which is close enough for amateur work (as long as the Q is
>reasonably high) though, certainly not mathematically precise to support
>the argument du jour. :-)
? With Eimac's *Care and Feeding of Power Grid Tubes* formulae, Q is
Definined as RL divided by the reactance of C1. There is no
approximation.
- On my Web site, there is an Excel 4 worksheet that performs
mathematically precise solutions to the Care and Feeding calculations for
those who are disinclined to exert themselves. // The bottom-line is
that a Pi-network (double L-network) is not resonant on the operating
frequency. If it were resonant, it could not transform. . . However,
it's close enough to resonance to act like a flywheel. // When I was
15, an OT (Keith Williams, W6DTY) told me that Pi-networks are more
complicated than they look. . . You were right, Keith.
>
- later, Marv
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|