Hello all,
I have a real doosey.

I built an Octopus, along the lines of the one which was featured in the Dec
2007 issue of QST. This article was written by Geoff Haines N1GY.

The Octopus is a 4 band rotatable dipole, using either Hamsticks or Workman
mobile whips

I fitted the following Workman whips: 75m, 40m, 20m & 15m.

I can tune all but the 20m whips, there is naturally an interaction between
each of the whips, but 20m simply cannot be tuned. its resonance is around
13.6mhz, and no matter what I do with the whip length it cannot be bought
into resonance.

I stress that 75m, 40, and 15m are great.

I have tried the 20m whips on their own as a single antenna and they tune
well, but as soon as I offer the second whip to complete the dipole, the
resonance drops to 13.6mhz.

When I refit all the other elements, it makes not much difference to the 20m
whips as far as their resonance is concerned, it does shift a bit which is
understandable.

I have tried rearranging the whips out of sequence around the hub, but that
made no difference.

Am I missing something, or are the Workman whips poorly designed?

Is there a preferred way of arranging the whips so that I do minimise
interaction between the elements?

Why are the 20m whips the only ones giving me trouble?

I am using an MFJ269 Pro to tune each band.

Thanks,
John
VK2KCE