In article ,
"John VK2KCE" wrote:

I intend to put a 2m/70cm antenna on top, but to do this I will have to do
some machining to the hub as it was machined out of a solid billet of
aluminium.

John-

Yours sounds like it is relatively weatherproof. Mine is definitely
not. It may be possible to use a round cap for a 4 or 5 inch PVC sewer
pipe to construct one that is. It might also be possible to mount all
10 elements of a 5-band antenna along the circumference.

A vertical 2m/70cm antenna would be worth a try. If it doesn't work
against the grounded HF elements, adding a few short resonant radials
should correct it. Worst case, a second feed line might be needed.

It occurred to me that my criteria for a "good dip" may be different
from yours. I consider it to be one that is distinct, at least 1.5:1
SWR but not necessarily down to 1:1. Using a rig that has an
auto-tuner, useable bandwidth should be at least as good as the spread
between 3:1 SWR points.

I made one additional modification to mine, swapping one insulated
element with one grounded element on the bracket. By pairing Ten and
Fifteen Meter elements as before, the previous problem seems to have
gone away.

(I'm having trouble posting, so this may appear twice!)

73,
Fred
K4DII