[Elecraft] K2 Antenna Tuner Question

[Julian (G4ILO)]

George,

Perhaps what you don't realise is that the KAT2 can be turned off from the
menu so that it is effectively out of circuit. The point of the suggested
exercise was to see how well the SG-239 matches the antenna compared with
the KAT2, just for curiosity, since the 239 appeared to be quite lossy when
installed at the feedpoint.

Personally, I suspect that any benefit in using an "optimum feedline
length" (presumably with the aim of presenting a matchable SWR at the TX
end) might be negated by the extra losses incurred by using a longer than
necessary length of co-ax. I have some charts on my web page that
demonstrate just how high co-axial feeder losses can be when the antenna is
a long way from 50 ohms. I claim no credit for these charts by the way:
they were produced using an Excel spreadsheet that was mentioned in an
article in RadCom about a year back.

73,
--
Julian, G4ILO. (RSGB, ARRL, G-QRP, K2 #392)
G4ILO's Shack: http://www.qsl.net/g4ilo

George, W5YR wrote:

I know this is obvious and pardon me for bring up what everyone
already knows, but it is really asking for trouble to allow two
automatic tuners in cascade to be operated at the same time. They will
chase one another's tails either until the operator gets tired of
hearing relays or the relays get tired and quit.  At QRP,  damage is
unlikely, but at higher power very high voltages and currents can be
developed between the tuners.

If you have in mind using the SGC first to tune the load and then turn
it off and connect its input to the KAT2, I suppose that would cause
no problem, although if the SGC has done its job, the KAT2 will see
only 50+j0 and be quite content to do nothing. Assuming that the SGC
is unable to attain that load for the K2, then letting the KAT2
"finish the job" should work. However, I would really be concerned
about power loss in the SGC under those conditions.