OK, at cecil's suggestion I changed to a single 20 segment wire with a
split I source at 50%. I ran the SWR plot against a 300ohm alternate
impedence. Is that the way to see what effect a 300ohm twinlead will
have? Now I get a minimum 2:1 SWR at 5.6Mhz and a pretty smooth convex
curve out from there to 14.5Mhz with a max SWR along that leg of around
35 at 12.1Mhz.

tnx
jtm