[Elecraft] SGC-239 vs KAT2

[Julian, G4ILO]

My antenna is approx. 80ft of wire looped around my loft. It is fed in the
center of one side by a SGC-239 autocoupler, which is fed using a few feet
of RG-58 co-ax to my K2 in my office on the floor below. This antenna works
better than I expected. However, I'm not over-impressed with the SGC-239,
which sometimes refuses to tune up, or jumps out of tune in the middle of a
QSO, and needs a carrier to be applied in order to know what band you're
on. The reason for this arrangement was so I could feed the antenna with
co-ax. Open wire feeder would be unacceptable in this environment.

With the SGC-239 not powered up, so that the RF goes straight through, I
find that the KAT2 can produce a good match on all bands. However, the SWR
reported by the K2 in CAL S mode on most bands is >9.9:1, and of the order
of 8:1 in the best cases, so I presume that feeder loss would be a bit
steep even though the co-ax is fairly short, about 18 feet. Also I suppose
that there will be radiation from the shield, due to feeding a balanced
antenna with an unbalanced line, though I guess that winding the co-ax
through a couple of ferrite rings a few times might fix that.

I'm wondering if it would be possible to feed this loop successfully using
co-ax and doing the tuning at the K2 end using the KAT2 which is redundant
in the current configuration. Is there a way to reduce feeder losses to an
acceptable minimum? Would putting a 4:1 or a 6:1 balun at the antenna feed
point reduce the SWR on the co-ax to a level where feeder losses would be
negligible? Would losses in the balun itself be significant? It would be
operationally more convenient to use the KAT2 with its ability to remember
the tuning position for each band, but as I'm running low power to a small
antenna I don't want to sacrifice more power to achieve that, so perhaps
I'd be better off sticking with the '239 and its idiosyncracies.

Thoughts, anyone?

73,
--
Julian, G4ILO. (RSGB, ARRL, K2 #392)
Homepage: http://www.qsl.net/g4ilo