[Towertalk] C31XR - 3 feeders

[Bob Henderson]

So far I only have one tower up so all my antennas are nailed to the one
mast.  I am experimenting with an SO2R installation that I have hung
together.

My antennas are a C31XR at about 22 metres with three seperate feedlines, an
XM240 at about 27 metres and Inverted Vees for 160 and 80 metres at about 22
metres.

Obviously I have interaction between these antennas but overall things seem
to work.

My question concerns the C31XR.  Does anyone have experience of using this
antenna with 3 feeders in an SO2R or M/S set-up?

In my installation I have adjusted the hairpin matches (I had to add one for
10 metres) and I now have SWR close to 1:1 at a selected point on each of
the 3 bands.  Until, that is..........I put any sort of load across the open
feeder to the 20 metre yagi when I am transmitting on 15 metres.  For
example, when I put a 10 metre stub across the 20m feed line the 15 metre
SWR jumps up to about 3:1.  Not good.

So far I have cobbled a fix for this by putting a 15 metre parrallel tuned
circuit in the 20 metre feed line on the antenna side of the stub which is
on the output of the six pack just behind the Alpha.  I made the tuned
circuit very high C and low L so it didn't screw me up too much on 20
metres.  It sort of works but I wonder if anyone else has experience of this
and has a more elegant solution?

Any and all words of wisdom appreciated!

Thanks

Bob 5B4AGN