[Elecraft] Remote Antenna Tuner

[Mike Harris]

G'day folks,

Not sure I want to put my head up over the wall again!  Actually, in my post
I said "where it should be" not "needs" but I won't split hairs over that.
OK, I accept that it  was perhaps a little too forceful, however, I believe
that there has been significant justification for the desirability under
certain circumstances for remoting the tuner.

The texts I have read on this subject have conveniently maxed out at 5:1
which neatly supports the low additional loss statement whilst at the same
time showing graphs clearly illustrating the much more unfortunate
consequences of higher SWR's.  It is clear though that antennas are
being routinely used at much higher SWR's than 5:1 I do it myself with
my 40 metre dipole used occasionally on all bands and losses in this
circumstance can be anything but insignificant.

A little story.  '74 through '76 I was running comms out of one of the
British bases in the Antarctic. I had a 1.5kW transmitter feeding 20 feet of
RG-213 class co-ax to a wideband 600:50 ohm transformer.  The parallel line
from the transformer went via a big knife change-over switch to the parallel
lines leading to two fat dipoles, one 120 feet and the other 60 feet spread.
On one occasion I had to broadcast weather forecasts to the field scientist
sledging parties on a frequency most unsuitable for either of the dipoles.
The SWR meter on the transmitter (Racal) was showing 20:1 and the Pi-L
output tuning was a bit tricky, razor sharp, but it coped OK.  After the
transmission (SSB) the co-ax clipped to the radio shack ceiling was hanging
limp, soft and unpleasantly warm.  The only frequency/SWR combo to cause
the problem.

We don't all have space for multiple antennas, and open wire feeders to the
house might not always meet with much XYL approval no matter how much we
think they look great and perform similarly.  Hence my "need" for a
conveniently remoted automatic tuner.

Actually there is another solution.  In the RSGB magazine "Radcom" there was
a design for a remote pic controlled frequency sensitive switch that could
be used for switching matching sections to tame high SWR situations.

Maybe we should draw a line under the thread and each go their separate
ways.

Regards,

Mike VP8NO (IOTA SA-002)
GQRP 10148
QRP-Canada #57
K2/100 #1400