[Amps] Amplifier 2x3-500Z

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Fri, 26 Mar 2010 11:45:16 +0100, "Gino" <gino at camporese.net> wrote:

>I need some information for amp 2 x 3-500z input circuit. I see many circuit but National XR-50 in no available.
>
>can you help me?
>
>many thanks
>
>IK3HZI Gino

REPLY:

A pair of 3-500Zs has an input impedance of very close to 50 ohms and
is an ideal candidate for the simplest of all resonant input circuits
- a parallel resonant coil and cap. Just connect them through a
bandswitch directly to the input connector, tune them up with an SWR
meter and you're done. 

If you keep the Q high enough, about 5 or more, you might be able to
get away with no parasitic suppressor at the anode. It's worth a try
anyway, if you feel a wee bit adventurous. That's what I did with my
8877 amp (also 50 ohms input) and it works like a charm. 

73, Bill W6WRT