jimbo wrote:
I have been trying to get an acceptable 2 meter antenna installed in
my attic. A J-Pole seemed to me the best solution for my attic space.
You may recall an earlier post where I discussed SWR on one of the
ladder line J-Poles I was working with. Well, I gave up on ladder line
and constructed a J-Pole from 1/2 inch copper tubing. I tuned it in my
basement work shop to give the best SWR and then took it up to the
attic. The following table shows the results.

Basement Attic

144 1.90 1.80
145 1.65 2.00
146 1.50 2.10
147 1.60 2.25
147.995 1.90 2.25

Actually, probably not that bad for a first attempt at copper tubing.
But, I didn't like the fact that SWR was above 2.0 in my attic and
that things changed between my basement shop and the attic. I guess
this design is influenced by objects close by.

So, somewhere in my surfing I came across the Arrow J-Pole. This is an
end fed, open stub commercial design that promises less that 1.5 SWR
across the band. Here are the results of my experiment with this antenna.

Basement Attic

144 1.10 1.22
145 1.18 1.10
146 1.25 1.20
147 1.30 1.32
147.995 1.40 1.42

Not 1.0 SWR but certainly met the promise. And the best thing about
this design is that near by objects don't seem to have an impact on
performance. If I built one of these designs and tuned it in my
basement shop, it should give the same results in the attic.

Anyway, just my subjective observations.

jimbo - AJ7IM

Hi Jimbo, it has been my experience, and everybody else's that an
indoor or attic J-pole is unpredictable. A high impedance end fed
antenna in an attic environment will be hard to predict. Moving it one
foot can effect things.
You might consider the SO-239 ground plane. It can be built and
tuned in 30 minutes, is 50 ohms, so it will not be so concerned about
its environment. Likely you could not tell a difference in performance
from a J-pole especially if they are both in the attic.
Oh yes, the standard-if the SWR is below 3.0, don't worry about it.
Gary N4AST