[Boatanchors] WTB - Antenna Tuner. . . . .

[Rob Atkinson]

the vast majority of those commercial tuners that claim to handle
balanced line really don't, or rather don't do it properly or very
well.  I have worked hams who have given up on balanced line, or have
all kinds of RF problems only to find they are using some coax tuner
with a balun somewhere between the tuner and the balanced line, either
at the tuner or outside somewhere.

To properly tune balanced line with no issues (common mode, RF in the
shack etc. problems) you must tune the line with a link coupled
balanced tuner that floats the balanced line above ground.  The
Johnson matchboxes do this.  short of homebrewing (which is fine thing
to do) nothing else out there on the market does this.   you can buy a
twin coil balanced tuner from Palstar but it is not link coupled and
will therefore pass common mode RF.  There is information on-line on
how to homebrew a link coupled balanced tuner.   Don't fall into the
trap of trying to get a coax tuner to do everything.  Even if it seem
to work you'll have greater loss in the balun, and at higher power
levels, heating during long transmissions.  This will be noticeable in
vswr changing.

73

Rob
K5UJ