Gary, 

What dimensions do you think are missing? As far as I can read, all of the
dimensions are that you need. As for the tubing diameter, you can use any
diameter tubing; though, I use 1/2" tubing. However, from my experience, the
larger the diameter, the better bandwidth and the less difficult in finding
the lowest SWR point. The article states that you should connect the coax in
a manner that will allow you to make adjustments quite easily by sliding the
connecting points up and down the tubing a little each way to find the
lowest SWR point. . I usually use something like a small hose clamp, or I
have even wrapped a piece of #14 bare, solid copper wire around the tubing
and twisted it, leaving one end sticking out to allow me to connect my coax
to it, and then, gently slide the copper wire up and down the tubing. Some
of my friends actually tact solder the feedline to the tubing, and then,
de-solder it and move it a little up or down and re-tact solder it, and
re-check the SWR, and keep doing that until they find the lowest SWR point.
Often you just have to experiment to find what works best for you.

Ron, K8HSY


-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Gary Tillinghast
Sent: Saturday, March 22, 2014 2:44 PM
To: [log in to unmask]
Subject: Re: How to construct a two meter j Pole Antenna

Some of the measurements are missing and no one mentioned what diameter of
tubing to use.  What should be used to hold the feed points to the antenna 
while making SWR checks?   KB2YAA

-----Original Message-----
From: Jim Gammon
Sent: Saturday, March 22, 2014 11:10 AM
To: [log in to unmask]
Subject: How to construct a two meter j Pole Antenna

Hi Linda, Thanks to Ron for this I found it on my Apex, 73, Jim WA6EKS How
to Construct a 2-Meter J Pole
  By Ronald E.  Milliman, PhD.  (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/d inches.  So you have a total length of about 79
1/d 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 equals 73
inches...or 58 plus 20 inches equals 78 inches.
  Of course, you want to mount the antenna in a location about 1/b 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


----- Original Message -----
From: "Linda C.  Knight" <[log in to unmask]
To: [log in to unmask]
Date sent: Sat, 22 Mar 2014 08:44:35 -0400
Subject: Re: Mag mount antenna and cookie sheet

Lol! This is why I love this group.  Thank you.

Somebody mention a jPole.  It slips my mind what is that.


Hugs and 73
Linda C.  Knight & shirley
CallSign: kk4hrg
Please note email:
[log in to unmask]


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