"Jerry" wrote in
:


"Cecil Moore" wrote in message
...
Jerry wrote:
"Owen Duffy" wrote:
http://www.vk1od.net/cobra/index.htm .

Says "Page not found"!

Worked for me.
--
73, Cecil http://www.w5dxp.com

Musta been a temporary thing. Worked shortly after I tried it again.

BTW, for whatever shortcomings Joe's Cobra has, I've had excellent
results and been complimented both on the ham bands and on some other
military/non-amateur frequencies I am authorized from 2-22 MHZ. So
long as it works! I'll probably do something else later, but at the
time, the Cobra was the best considering personal considerations and
lot limitations. And, actually, I am not one of those who must have
the biggest signal going--just so you can hear me well enough to do
the job!

Jerry, it seems to me that the Cobra is a compromise, and we each make
our own judgements about the trade-offs that are acceptable. Of course,
those individual considerations make recomendations like "it works great
for me, it is the best for you" rather worthless.

Some of the claims about some antennas (including the Cobra) seem
unrealistic, but that doesn't condemn the antennas, it just means people
building or buying them based on those claims have been mislead.

It is my view that understanding the behaviour of the antennas helps you
to make an informed judgement about the trade-offs in your own situation,
and it allows you to get the best out of the antenna as installed.

Modelling suggests that the Cobra Jnr has a couple of weaknesses, one is
the spikes in loss at some frequencies (an artefact of linear loading),
most but not all of which are outside amateur bands; and the second is
that the "window" of low loss around 80m is narrow and might be worth
checking that as installed, that window is centred over your most
desirable operating frequncies. These effects scaled for the double size
are more pronounced with the full sized Cobra.

An effect similar to the second point above exists also with the G5RV,
and I have suggested a procedure in-situ tuning for optimising 80m
performance. If I had a full sized Cobra and intended using it on 160m,
or a Cobra Jnr on 80m, I certainly would think about doing similar.

Owen