[Amps] PI-L Thoughts!

[Ulf (SM0NOR)]

Thanks. This sounds better than pushing the Q on the higher bands. I'll look into it. Maybe it is better described in earlier editions of the handbook. I have at least one from each decade, so I'll go back and do some reading!

Sent from my iPad

On 11 dec 2010, at 21:15, "Bill, W6WRT" <dezrat1242 at yahoo.com> wrote:

> ORIGINAL MESSAGE:
> 
> On Sat, 11 Dec 2010 19:26:16 +0100, "Ulf (SM0NOR)" <ulf at sm0nor.com>
> wrote:
> 
>> This makes me think of a third solution mentioned in the handbooks 
> 
> REPLY:
> 
> There is a fourth solution that is easier than all the others put
> together. It is disappears in depth in any of the ARRL Handbooks of
> recent years. I have used it myself on a six meter amp and it works like
> a charm. 
> 
> You create a simple L-network in the plate circuit by adding a small
> coil, typically about .5 uH or so directly from the tube's plate
> connector to the rest of the circuit. The coil together with the tube's
> internal  plate to grid capacitance creates an L-network that steps the
> tubes native plate impedance down to a value which the otherwise large
> tune cap can handle with reasonable Q. 
> 
> It sounds like black magic but it works. Get an ARRL handbook if you
> don't already have one and look it over. It's in the chapter on
> amplifier design. The best part of the design is its effect disappears
> as you go lower in frequency and it has almost no effect on the lower
> bands. 
> 
> The best of all worlds.
> 
> 73, Bill W6WRT
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