arrow antennas makes a nice one that can clamp to a mast.  It is aluminum 
rod and I have had one up for about 9 years and it still works well.
----- Original Message ----- 
From: "Ronald E. Milliman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, August 27, 2012 6:49 PM
Subject: Description of a J Pole antenna


> Howard,
>
> several days ago you asked if one of us could describe a J Pole antenna to
> you in enough detail so you could build one.  Well, I will try.  Here it
> goes...
>
>
> construction for a 2 meter J Pole :
>
> First, imagine the print letter J . This represents the shape of the
> antenna. It has one long side and one short side all connected at the
> bottom or said another way, one continuous length of conductor shaped into
> a J.
>
> Now turn or flip the J backwards as if you were writing it with the short
> side on the right rather than on the left.  I say this simply because this
> is the way it is usually shown in the ham mags and on most web pages.
>
> The J is one single "conductor" in the shape of a J.
> From the top of the long side of the J to the bottom, for 2 meters, is
> about 58 inches long before it turns horizontally a couple of inches and
> then goes vertical for about 19 1/4 inches. So you have a total length of
> about 77 1/4 inches forming a single J shape.
>
> The center conductor of the coaxial feedline is attached to The long
> section of the J Pole and the braid or shield of the feedline is attached
> to the short section.  These feed points for the coax are spaced up from
> the bottom of the J or antenna about two inches, and they need to be,
> initially, adjustable , until you find the optimum tap or feedpoint that
> gives minimum SWR. So, do not make a permanent feedline connection yet.
> Once you have these feedpoints adjusted to produce minimum SWR, you can
> solder them for a permanent connection.
>
> Again, the shield of the 50 ohm coax is attached to the short section 
> about
> 2 inches up from the bottom.
> The center conductor of the 50 ohm coax is attached to the long section
> about 2 inches up from the bottom. Both the center conductor and the 
> shield
> should now be side by side on the vertical elements equal distance from 
> the
> bottom. One on one vertical side and the other on the other vertical side.
> BOTH are connected equal distance from the bottom of the antenna and are
> adjusted up or down equally for lowest swr. This is the tricky part. Some
> method of making temporary connections for tuning will be needed or they
> can just be tack soldered for testing and tuning.=20
>
> For tuning, you can mount the J Pole on top of a short pole, a length of
> PVC, a push-pole, etc., or you can mount it on a temporary support like a
> wooden ladder.
>
> Then, once you have it tuned, you will need some method of mounting the
> antenna to a mast, pole, etc in your final installation.
>
> Most builders just add about 15 to 20 inches to the long side at the 
> bottom
> for mounting.
> This extra length becomes invisible to the operation of the antenna; thus,
> not effecting its operation.  So, it can be metal tubing for a J pole.
> Adding this length would make the long side about 58 plus 15 inches =3D 73
> inches...or
> 58 plus 20 inches =3D 78 inches.
> =20
> Of course, you want to mount the antenna in a location about 1/2 wave
> length away from any metal surface near the antenna in any direction 
> except
> the bottom of the antenna.
>
> The lengths and spacing of the J element is not very critical due to the
> variable tuning section. The main thing is to get the final swr down as 
> low
> as possible.
>
> Also, it is recommended to add about 4 or 5 turns of coax in a neat coil
> with coils side by side at the bottom of the antenna making an air 
> choke=9D
> out of it to keep stray rf off of the coax outer conductor.
>
> It is a challenge to describe something like this, but there you have it.
> I hope you are able to visualize it well enough to take a shot at actually
> building one.  Alternatively, they are available to purchase either fully
> assembled or the parts that you can put together yourself. =20
>
> Ron, AC4HM