Now I am frugal and am a bit of a scrounger. I didn't want to invest a lot of money in copper pipe and I had an old VHF TV antenna that was wind damaged. Its a yagi style with the reflector element being 2 u shaped peices of aluminum vaguely resembling a trombone slide. Their are 2 of those and neither one was damaged except at the base where they attached to the boom. I proceeded to cut them off the boom. cut them to size and attach them together to make a slimjim. our local repeater is at 145.13 mhz so the slim jim was made to the following specs.
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The long side is 58" I joined the two peices together with a double
tapered bolt like those used to join two peices of wood together in
furniture. I used a small hose clamp on the outside of this area to
hold the tubing tightly to the threaded bolt and to make a good
electrical connection. The open side consists of a 19.5" leg and a
37" leg. If one looks on the internet you can find calculators for
cutting this exactly to your desired frequency. Here
is one that gives deminsions in mm.
I used hose clamps to attach the coax to the slim jim about 4" from
the bottom. Center conductor goes to long side shield to "open"
side. you will need to slide this attachment point up and down until
you find the best swr reading. The design i used to model this
antenna suggested a much lower point for the feedline but i found
through trial an eror that this modification of the design needed it
to be higher. The higher you attach the feedline the higher in
frequency it will be tuned for. After a bit of trial an error I got
it tuned to a 1:1 swr.
This antenna should be attached to some pvc pipe and the antenna
needs to be at least 19." above the metal mast. In the photo above I
have it attached with tape but plan to try using large zip ties
before I put it in it's permanent location.