2m Slim Jim Antenna - One Year On.

A year or so ago, I built a copper tube Slim Jim antenna for 2m.  This was for general coverage of the local area, and I hoped it would be as good as people claim.

Boy, is this a superb antenna!  Not only is it super-strong mechanically, it's a superb 2m antenna that costs just a few dollars to put together.  Quite why anyone would pay for a piece of wire encased in some glitzy-labelled fibreglass tube is beyond me, when something like this is a real joy to make and a pleasure to use.

Even though the antenna base is only at 3m we are, admittedly, at an elevated QTH (100m amsl), and have a clear shot across the sea to the Isle of Man and Ireland.   Nevertheless, this provides a truer picture of the potential of the Slim Jim, rather than telling you how much an urban setting is robbing your waves of energy!

Matching wise, a good quality VHF or wide-coverage HF/VHF SWR meter lets you see how the SWR changes by sliding the coax tails up and down.  Eventually, you find a 'sweet spot', and solder them on.  I don't recommend using pipe clips - they either rust or become loose.  Solder and then amalgamating tape is best.

When soldering, blast the copper, which should be rigorously cleaned with wire wool first, with some gas blowtorch heat for a minute or so to get it really hot, then melt some solder onto the proper spot.  If you prepare pre-soldered coax tails, you'll find the copper tube momentarily retains enough heat to melt the coax solder and make a good connection without much or any further application of the blowtorch that otherwise tends to also melt the coax plastic!

Detail of the mounting found to work best by far.

Mouting the Slim Jim is a little fiddly.  I eventually used plastic snap-over pipe clips screwed to a back panel of pressure-treated timber (e.g. 1.5" x 1.5")  A very short section of plastic or varnished bamboo cane is inserted between the bottom of the antenna and a short copper tube below (which is merely a mechanical stabiliser)  Just using a longer length of bamboo or plastic leads to a weaker mount.

Superrefraction of the Isle of Man hills.  Expect very good VHF conditions when this happens!

With just 5W out, my little copper tube creation easily and consistently opens and gives a very good output signal on repeaters at 50 miles.  When there is some superrefraction ongoing, that extends the coverage substantially.

So, ignore the bun fights about just exactly how much gain a Slim Jim has, and relative to what radiator that is.  Practical experience shows this antenna does indeed provide very low angles of radiation, converting a lowly handheld into a regionally-capable transceiver.

As usual, the advice is: go build!