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[Amps] G-G Amplifiers With No Tuned Input.

To: <amps@contesting.com>
Subject: [Amps] G-G Amplifiers With No Tuned Input.
From: 2 at vc.net (2)
Date: Sat May 3 17:37:14 2003

>Rich: that sounds like an interesting idea.!!
> I'm working on a gla1000, plain model, modified with
>EL509's, and would love to test such an idea. I have tried several other
>things, like tuned inputs, a broadband input transformer, and not had much
>luck . what is the no. of the diode you mentioned.???

**  I purchased ten of 'em to distribute free for R and D.  Are you still 
at 7509 Wakulla Dr. ?  
--  My guess is that the input terminator R that the diode goes in series 
with should be 50 - 75 ohms.  If you try the idea, please post your 
findings on AMPS.  Need a termination R ?

have phun, Carl

>   carl / kz5ca
>----- Original Message -----
>From: "2" <2@vc.net>
>To: " AMPS" <amps@contesting.com>
>Sent: Thursday, May 01, 2003 3:27 PM
>Subject: [Amps] G-G Amplifiers With No Tuned Input.
>
>
>> Amplifiers such as the MLA-2500, SB-230, 374, 78, and 76PA have no tuned
>> input.  This is not a problem when such a g-g amplifier is driven by a
>> tube-output radio such as the TS-830S.  The reason is that although the
>> input Z of a cathode-driven triode fluctuates from roughly 1/3 of the
>> average driving Z on negative peaks to a virtual open circuit on positive
>> peaks, the Pi-network tuned circuit in a tube-output radio acts as a
>> flywheel to smooth out the Z fluctuation at the cathode/s.  However, with
>> modern solid-state radios there is no tuned output, so something is
>> needed to smooth the Z fluctuation.  A possible workaround, short of
>> adding a bank of tuned input circuits, might be to put a ultra fast
>> recovery diode in series with the input terminating R.  The diode is
>> oriented so that the terminating R conducts only when the driving
>> potential is positive -- which is when the tube is not conducting..
>> Thus, on the negative half of the driving cycle, when the tube has a low
>> driving Z, no driving power is lost in the terminating R and the driver
>> should see a lower SWR.
>> - -  Unfortunately, I do not own such an amplifier to test the idea on.
>> If anyone out there has such an amplifier and is willing to test this
>> idea, please inform me and I will send you a freebee 2A, 35nS, 300v
>> switch diode.
>>


-  R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K, 
www.vcnet.com/measures.  
end

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