[Elecraft] [K3] KAT3 and 160 with 40m long doublet

[Stephen Prior]

I have only just recently added the KAT3 and I'm very impressed with it, but
given the praise heaped upon it by others I'm slightly surprised that the
best VSWR I can get on 160m is about 8:1.  The antenna is approximately a
doublet which is a half wave long on 80m ­ I say 'approximately' as it's
slightly off-centre fed.  I have about 7m of 300 ohm slotted down from the
feedpoint and then into a coaxial choke at roof level for the remaining 10m
into the back of the K3.  Substituting the straight connection for a 4:1
balun (Guanella) at the transition between the slotted feeder and the coax
helps slightly but not by much.

Unfortunately I don't have a vector analyser,  so I have no idea of the
nature of the reactance that the K3 is seeing.  However, given the
wavelength involved, I would need to add a very significant length of
coaxial cable if I were to swing the point around the Smith Chart.

I have tried to manually tune the KAT3,  but unless I am missing something,
I am am not able to change the L and C values at the same time as
transmitting, so it's a very tedious process.

Tomorrow I may well add some extra wire to hang vertically down from the
ends of the doublet.  In the meantime I would be pleased to hear any
comments.

Happy New Year!

73 Stephen, G4SJP