"Mark Keith" wrote in message ...
Richard wrote:

A simple fast way to design an NBS yagi for any freq, is to use the
eznec demo. It has a NBS yagi as a demo, and it can be easily scaled
for any freq. MK

Okay, but aren't these models only sufficiently accurate if you use the
dimensions in the models to build an actual yagi, if the boom is non
conducting?

I don't worry about the boom. It's effect on the antenna is small. All
my booms normally are metal.
Is it not true that if the boom is conducting you cannot rely on
the model dimensions?

I don't think it is to any great degree worth losing sleep over. I built
the eznec NBS yagi for 6m, and used those dimensions, using my own
construction techniques, and it came out nearly perfect as per the
model, and modeled results. To me, you are taking a simple task, and
overly complicating things by insisting on utter perfection in element
diameters, boom, element mounting, etc. For a VHF receive 3-4 el yagi,
it's just not *that* critical. When I built a marine yagi, I paid little
attention to exact element dia, mounting , boom, etc. I used coathanger
wire welded directly to the copper tube boom. I didn't try to optimise
the lengths, etc. In fact, this was waaaay before I'd ever seen a
modeling program. It still worked just fine.
MK

--
http://web.wt.net/~nm5k

What has happenned is that I, who know little of the art, am relying on
whoever condescends to make a comment. And comments so far have tended to
highlight how unsatisfactory it is taking a model and bulding a yagi on the
dimensions. There seems to have been a desire to point out to me how
impossible a task it is to build a decent antenna unless one factors in
alteration of boom size and element diameters. Technically these comments
are correct, you cannot expect to get the same antenna performance if these
things are ignored and I feel I've been concentrating on these details for
fear of not doing enough. But on the other hand, will the difference on
receive amount to much whether elements are insulted from a boom or not .
Probably not eh.