----- Original Message -----
From: "Jim Barber" <audioguy@q.com>
To: "Manfred Mornhinweg" <manfred@ludens.cl>
Cc: <amps@contesting.com>
Sent: Saturday, August 06, 2011 2:39 PM
Subject: Re: [Amps] Plate Cap Quandary
>
> I wasn't paying attention when the beginning of the thread marched by,
> thus the bad timing.
The full thread is in the archives.
>
> So: center-tap the 10m coil with the Tune C, then just leave the
> "left-hand" end open?
No it goes to the tube.
>
> 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... ?
Its especially helpful with that and similar tubes and since a vacuum cap is
needed the min C is a bit less.
The MRI amps operate close to 6M and a few Europeans have supposedly got it
to work on 2M or are still scratching their heads...I havent been following
it closely.
Carl
KM1H
>
> 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.
>>
>> ========================
>> Visit my hobby homepage!
>> http://ludens.cl
>> ========================
>> _______________________________________________
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>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
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