If I remember right, the TT is series inductor, shunt capacitor. The TT 229
and 238 come with about a 500pf variable, and has the ability to switch in
approximately another 2500pf (and it may need more on 160, and that's why
they put the connection on the back for additional capacitance). Since I
haven't looked this up in a while, I could have it backwards, but here goes
anyway. If the impedance is low, the shunt fed component is fed. If the
impedance is high, the series component is fed. The TTs have provisions for
this. It will only match in one place, and that is the most efficient.
Wouldn't be without mine. although I am building a super "L", with a
8-1000pf vacuum variable, 3000pf of switch in additional capacitance, and a
28mh roller. If I ever get the time to finish it, then, and only then, will
I let my TT229 go. (The only reason I am building it is that I think that
everyone should have at least one major piece of equipment that they built
in the shack. This tuner will be mine.). Cheers. Vern
----- Original Message -----
From: "Bwana Bob" <wb2vuf@qsl.net>
To: "Stuart Rohre" <rohre@arlut.utexas.edu>
Cc: <tentec@contesting.com>
Sent: Thursday, July 03, 2003 6:54 PM
Subject: [TenTec] Re: L net tuners
> That's a clever idea. In my reading on L networks, I usually see a
> series inductance and shunt capacitance at the output end, but the
> antenna book says that a shunt L and series C can also be used. I
> haven't seen this configuration anywhere. How is the TT model 238 wired
> and how much capacitance is used? Is 400 pf enough?
>
>
> Bob WB2VUF
>
> Stuart Rohre wrote:
> >
> > A simple mod to the Ten Tec T kit ground tuner converts it to a
transmatch
> > of the L network type. It is normally a series variable L , fixed
series C
> > (switched values).
> > A bit backwards to most L tuners, but it works. The mode insulates the
mid
> > junction of L and C and converts it to coax jack.
> >
> > Instead of being set up only to series tune a ground wire, you can L
tune an
> > antenna, or use a shorting plug and go back to ground tuner
configuration.
> > Just reverses some existing wiring to turn the circuit around.
> > 73,
> > Stuart K5KVH
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