[Amps] Plate Cap Quandary

[Jim Barber]

I wasn't paying attention when the beginning of the thread marched by, 
thus the bad timing.

So: center-tap the 10m coil with the Tune C, then just leave the 
"left-hand" end open?

The YC156 suffers from high Cout as well, but theoretically has gain up 
to around 110mhz assuming I remember correctly. Perhaps this trick would 
work there as well... ?

Thanks,
Jim, N7CXI

On 8/5/2011 7:12 PM, Manfred Mornhinweg wrote:
> Hi Carl, Marv,
>
> I was about to suggest to simply reverse the order of things, and do this:
>
> 1) add up the tube's capacitance, stray capacitance, and minimum
> capacitance of the plate tuning cap;
>
> 2) Calculate the PI network for that input capacitance, which will
> require a higher loaded Q than the one your original capacitance spec
> was based on;
>
> 3) Put up with the more critical tuning and higher losses caused by this.
>
> But after reading Carl's suggestion,
>
>> Simply wind the 10M coil as per the software program using your favorite Q
>> while ignoring any C. Then center tap that coil with the Tune C; it will be
>> 4X ratio so now you need 4X the C to resonate.
>>
>> The effect carries thru  the other bands and rapidly becoming unoticable.
> I cannot do anything else than bow my head to long-standing experience,
> and mention my own idea just for its anecdotical value! Do what Carl
> says, Marv...
>
> I will go back to my MOSFETs instead. My experiments are advancing. I'm
> fighting device capacitances too, but in another way... I hope that in a
> few months I will be testing a low cost mosfet legal limit amp on the air.
>
>
> Manfred.
>
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