After trying the "T" based on published designs, I hate it. My 2nd HB
50 MHz amp, with a Pi using front-panel adjustment shafts, is completely
flat even though I used the wrong tube Z in computing the values (used 90
ohms instead of the more realistic 40-50 for a GS35b-they are not published
anywhere so I took a SWAG). No matter, flattened out without a bit of
trouble & not "sharp" either, easy to tune & forget. My GS35b T on the
other hand is so darn hiQ that a heartbeat or metal screwdriver used during
/ for adjustment will throw it off by a bunch. Also used a Pi on a
3CPX800A7 (SB200 chassis but essentially completely HB for the 8R
Dxpedition) & it loved it as well. You could get by easily with a T using a
variable inductor (K5AND et. al. use that method), but unless you have one
of the appropriate value, air variables of the appropriate size are easy to
come by, at least here, and the fixed inductors are a 2 minute build (& for
pennies in magnet wire).
Bottom line, I'd use a Pi & live happily ever after.
Dave N3DB
----- Original Message -----
From: "TL_IARC" <4z4tl@iarc.org>
To: <amps@contesting.com>
Sent: Friday, March 19, 2010 1:48 PM
Subject: [Amps] "Pi" or "Tee" input circuit for a 50Mhz
> Hello all
>
> Trying to decide between a "Pi" and a "Tee" input circuit, for a 50Mhz
> single 3-400Z amp.
>
> (formerly AL-80A with 3-400Z reploaced).
>
> Any thoughts please?
>
> Thanks in advance, Isaac, 4Z4TL
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