Ron:

This is absolutely excellent, and hopefully, will benefit more than just me.

Thanks so much.

Tom Behler: KB8TYJ

----- Original Message ----- 
From: "Dr. Ronald E. Milliman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, August 17, 2013 4:28 PM
Subject: How to Construct a 2-Meter J Pole


> How to Construct a 2-Meter J Pole
>
> By Ronald E. Milliman, Ph.D. (K8HSY)
>
> 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 publications 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 79 
> 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 feed point that gives minimum SWR. So, do not make a
> permanent feedline connection yet. Once you have these feed points 
> 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; that is, 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.
>
> 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
> affecting its resonance.  So, it can be metal tubing for a J pole. Adding
> this length would make the long side about 58 plus 15 inches = 73
> inches...or 58 plus 20 inches = 78 inches.
>
> 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, to keep stray RF off of the coax outer conductor, it is highly
> recommended to add an air choke at the bottom of the antenna. For 2 
> meters,
> the coil is 4 turns of coax with coils side by side in a neat coil 5 
> inches
> in diameter. You should get good results with the choke within 3 or 4 
> inches
> of the feed point. You can simply use the last part of your feedline as 
> the
> choke before attaching to the feedpoint!
>
> Hopefully, I have described this antenna well enough so you can construct
> one if you want to give it a try. Alternatively, they are available to
> purchase either fully assembled or the parts that you can put together
> yourself.
>
> Good luck!
>
> Ron, K8HSY
>