[TenTec] 1251 T kit

[Stuart Rohre]

The 1251 is pretty straightforward. It is a series tuned circuit placed 
in series between the rig and a counterpoise wire.  The circuit uses 
switched FIXED high voltage ceramic capacitors (one in the circuit per 
step), and a toroid would with taps for the variable element in series 
with the cap selected by switch.  The meter is set up to show relative 
current, and you tune for maximum meter indication to indicate resonance.

It is based on the principal that a series tuned circuit is lowest 
impedance and highest currrent at the resonance point.  With the 
associated series wire, you can replicate a longer counterpoise by the 
tuning selection of the 1251 L and C.

Back in the 90's, I came up with a way to modify the 1251 to also act as 
an L network tuner, if not needed as a counterpoise tuner.  This became 
an article in "QRP Quarterly" of the QRPARCI club.  It was done such 
that a plug in connection was all that was needed to go from one 
function to the other.  And adding one connector was the only extra part 
used.  It did require altering the position of the L and C as to which 
was first in the circuit, but that is transparent to a series circuit.

I posted many comments on the "Artificial Ground" modification to use as 
a tuner.  They are either in the archives of this list or that of QRP-L 
listserver.

-Stuart Rohre
K5KVH