[Amps] low Q output matching

[Bill Fuqua]

L network is the lowest Q resonant approach you can use.
The  Q is the Square root of the ratio of the input and output impedance.
Bill wa4lav


At 08:23 AM 11/12/2012 -0800, Bill Turner wrote:
>ORIGINAL MESSAGE:
>On Sun, 11 Nov 2012 17:59:26 +0000, Manfred wrote:
>
> > When you push a tube
> >with rather high capacitance to a relatively high frequency, you can end
> >up forced to use a Q of 20 or 25 or even higher, just to absorb that
> >high tube capacitance!
>
>REPLY:
>This question comes up often but there is an easy solution.  Placing a simple
>coil between the tube anode and the input to the tank circuit can 
>transform the
>tube's output impedance down to a lower value which can be easily matched 
>with a
>relatively large tune capacitor. The coil forms a simple "L" network using the
>tube's output capacitance at high frequencies. At lower frequencies, the "L"
>essentially disappears. The best of both worlds.
>
>I have used this technique several times. It works like a charm.
>
>For a full explanation, see any recent ARRL handbook in the amplifiers 
>section.
>
>73, Bill W6WRT
>
>
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