Right on Colin!....Jim K7RDX
----- Original Message -----
From: "k7fm" <k7fm@teleport.com>
To: <Amps@contesting.com>; "Will Matney" <craxd1@ezwv.com>
Sent: Wednesday, January 19, 2005 5:23 PM
Subject: Re: [Amps] Tetrodes in GG Configuration
> "What I can,t figure is why one would want to run a tetrode in G-G where a
> triode is the very ticket for it? To me, if one wanted to run a tetrode,
> they would want to run it the way it was designed to run in the first
> place."
>
> There are some very good reasons to run a tetrode in grounded grid. Using
> the 4Cx1000A as an example, running it grid driven will result in
> unacceptable distortion products. To get acceptable levels you must
> increase the inverse feedback. Grounded grid inherently provides feedback
> and will improve the distortion products by about 6 db. Collins ran the
> 30S-1 with a 4CX-1000A in grounded grid, but also added negative feedback.
> The result is an amplifier significantly cleaner than the tube itself.
>
> A second reason is cost and availability. A 3-1000 is almost impossible
to
> find. New, they are probably $750. However, a 4-1000 run grounded grid
is
> available used for about $100. The only penalty is a requirment of 1,000
> volts additional plate voltage. But, the proper ham can build a power
> supply with an additional 1,000 volts for less than the $650 price
> difference.
>
> Not many years ago, I bought a used amp with a 3-1000 final. I then sold
> the tube for more than I paid for the amp and plugged in a 4-1000.
>
> 73, Colin K7FM
>
>
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