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Re: [Amps] XCVR Output vs. Amplifier Input Impedence

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Subject: Re: [Amps] XCVR Output vs. Amplifier Input Impedence
From: "Wayne Rogers" <>
Date: Sun, 9 Mar 2008 13:37:58 -0400
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This discussion about the output impedence of a solid state transceiver has 
some bearing on my current problem.

I am beginning to build a 4-1000A G-G linear (I know - old technology, but 
thems the parts I have).  I am trying to figure out the best approach for 
coming up with an input network.  My research to date says that the 
impedance varies snywhere from around 25 to 200 ohms, frequency dependent, 
and I would guess is dependent on some of the input components (like the 
bifilar choke on the filaments).

So how do I approach the design?  I am planning on a pi-network with a Q of 
3 or so.  The values are easy to calculate if I know the tube input 
impedence, but I don't.  I could design for 100 ohms and hope for the best? 
Also, with a  low Q I'm expecting to have only one of the three pi-network 
components variable, but which one?  What has your experience been?  I am 
building this amp for the low bands - 160 - 40, so I won't have to deal with 
the problem of making a 4-1000 play on ten meters.

Any input appreciated.  Thanks in advance.

Wayne N1WR 

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