On Mar 6, 4:30?pm, Michael Coslo wrote:
wrote:
You can read AG6K's article he
http://www.somis.org/bbat.html
and judge for yourself.
I have gathered the parts to make just that!. I'd have it up now, but I
switched to a coax fed antenna for a while, and built a more traditional
tuner. In the interim I went back to balanced line.
The AG6K tuner can be used with balanced or unbalanced
line.
All you have to do to use it with an unbalanced line is to ground the
coax shield at the tuner end of the coax balun,
and use the "other side" to feed the ungrounded line. A
simple SPST switch of adequate ratings can do the job.
The AG6K tuner, as described, has adequate matching
range for most dipole-fed-with-balanced-line amateur
antennas. A little care in choosing the antenna and
feedline length can make the tuner's job a lot easier.
Reg Edwards' DIPOLE3 program can be a big help in
figuring out the shack-end impedance of various
antenna/transmission line combinations.
AG6K's approach used two ganged roller inductors and
a single variable capacitor, compared to most commercial
manual tuners that use two variable caps and a single variable
inductor. Because there are only two controls, remoting the
tuner is made easier.
Some day I'll report on how mine is doing. In the present situation I
don't need remote tuning, but will probably motorize the unit anyway.
Although not mentioned in the article, the roller inductors
could be replaced by a pair of tapped coils and a double-pole switch.
The tap positions would have to be found by
experiment, but could be made permanent once they were found. Tuner
adjustment could then consist of simply selecting the correct tap
postion with the switch, and
adjusting the variable capacitor for minimum SWR.
Automatic tuners are not new to amateur radio, btw.
An automatic balanced tuner was described in QST for July, 1952. It
would automatically retune itself within
an amateur band. Changing bands meant changing coils, but once that
was done the tuner would do the rest automatically.
73 de Jim, N2EY