> I have modified my kW Matchbox exactly per the circuit presented
> by Cebik. In series with the primary coil is now a 0 - 500 pF
> variable, and each of the five turns of the primary link coil is
> now tapped; thus 1 turn through all five may be switch selected
> to tune the primary circuit by switching the L and setting the
> variable series C. On 80 meters, the setting is 4 primary coil
> turns and about 200 pF series capacity.
Finger hit the 2, should be about 300 pF series C on 80 meters;
varies throughout the band, of course. Note that Cebik suggests
when building up a link coupled tuner from scratch, the secondary
inductance and capacitance should be a ratio of exactly 10X's the
primary L and C values. This precise ratio is not part of the
original Johnson design, but, never mind, works fine as mine
is modified. I use four primary coil turns on 80, and three turns
on 40 up 17 meters. One turn is sufficient for 15 and up. 12
and 10 meters would be better with only a fraction of the first
primary coil turn, but I have not bothered to do that.
There is "no way" to get the original kW Matchbox to operate
on 160 meters. The inductors would have to be
about doubled in length, and the unit might well no longer operate
as well on the higher bands.
73, Jim, KH7M
--
FAQ on WWW: http://www.contesting.com/FAQ/tentec
Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
|