[Amps] High C out

[Bill Fuqua]

For an L you need the capacitance on the high-z side. The capacitance 
should be from  plate to ground and the L in series with the 50 ohm 
load.  Q is the square root of the impedance ratio. You need adjustable L 
and C to match on all frequencies.

Oddly enough I have seen it used but when I tried it with my 4-1000 I could 
not get it to work. I will revisit it some time or another. I had hoped to 
use a L output on my amp and then follow with switched low pass filters 
which could be use with any of my amplifiers but simplify the amp itself.

73
Bill wa4lav


At 02:03 PM 1/21/2005 -0500, Dennis12Amplify at aol.com wrote:
>
>In a message dated 1/21/05 12:49:50 PM Central Standard Time,
>vic at rakefet.com writes:
>
>Nope,  he's talking about adding some inductance between the plate and the
>tune-C, making a kind of "L-Pi" (or L-Pi-L!) network.  The idea is  that with
>very high plate load impedances it may be impossible to get a  low-enough
>minimum
>capacity in the tune-C to permit a reasonably low  Q.  Adding some inductance
>before the Pi network pre-transforms the  load impedance to a lower value so
>a
>practical capacitor can be  used.
>
>
>
>I agree.
>
>  He's creating a two stage impedance transformer.
>
>  I'm sorry but I consider a Pi network a Pi network no matter which  end is
>connected to where; and I know that the large C is on the low impedance  side
>of the impedance transformer. I did't realize I was in error calling it 
>a  Pi-L
>network instead of an L-Pi network, but I guess I can see where some may  get
>confused. I DID state that the PLATE C became the new TUNE C in  that
>configuration.
>  I have used it myself in some cases to UP-CONVERT impedances to  obtain a
>reasonable tank Q.
>  A good example being multiple sweep tubes in parallel where the 
> total  plate
>capacitance is greater than 50 PFD. I have also used similar  circuitry to
>match the Collector impedance from the output of a single  ended transistor
>amplifier before we started using broad band transformers to do  the 
>impedance
>matching, but once again that was for converting a low impedance  to a 
>higher one.
>
>Dennis O.
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