I'm building a near copy of the F9FT 55 element. The original F9FT
antenna mounted the elements on tall plastic pillars, presumably to
minimise boom effects.

I have used use lower profile water pipe clips, suitably drilled ( the
boom is 15mm stainless steel water pipe) so the elements are closer to
the boom than the original.
Tall pipe fixings are available but I didn't like the mechanical aspects
of this approach.

When I modelled the antenna in NEC2 with the closer boom, I found no
difference to the impedance and radiation pattern .I had expected to
have to re-optimise at least the feed point. I got the same answer in
MMANA.

The questions I have a- Were Tonna being overcautious ? Is my
modelling software inadequate for boom effect modelling .

I think the F9FT design is based on the DL6WU design, so is possibly
less critical to these effects.


Brian GM4DIJ


--
Brian Howie