2M Square Dipole by KØFF

The 2 meter Square Copper Dipole by KØFF

Here is the parts list and dim. sheet for a 2m square dipole, made from copper water pipe. (Click on the diagram to see a larger version)

It is more or less omni-directional, and horizontally polarized. You can even make it from the short pieces of pipe left over from the 6M project (see 6 Meter Square Copper Dipole by K0FF). It presents a low through high angle of takeoff , and is intended for use in the 144.200 area, although it’s wide enough to use as an AO-27 uplink, and can handle 100W. It’s particularly useful on AO-27 when the pass is very high or overhead, and in the “cone of silence” of a fixed vertical. I use this for mobile satellite uplink, and wave a short handheld 430 antenna out the window for receive. Excellent results from SSB mobile too, where I’ve been able to talk to other mobiles similarly equipped 200 miles away. The mounting arrangement allows it to be affixed to a standard mobile mast that presents a 3/8 x 24 male thread (ALA Hustler base mast). You run coaxial cable right to the antenna and connect it to the built in SO-239. The only adjustment on it is the Gamma match, as resonance is set by the design dimensions.

It's just a dipole folded around on itself. The shape is an open 11” with mounting via a copper TEE with the open end down. In that open end solder a 1/2" brass rod which has been drilled and tapped for 3/8-24. For stacking a pair, you could make the TEE and threaded insert come horizontally instead, and mount one antenna above the other. (Future articles will give detailed info on stacking antennas in general). Stacked antennas provide improved gain and power handling capabilities. Side mounting on a tower can be achieved by using conduit clip large enough to go around the mast (or tower leg), and run a 3/8 x 24 s.s. bolt into the threaded fitting.

Solder the antenna parts together per the drawing using the 90 degree elbows at the corners. Cap the far (open) ends and mind the gap. All measurements are critical. The brass plate* to hold the SO-239 is bent to form an "L" 1-3/4" tall with a 1/2" lip. A 5/8 hole is provided 1-1/4 inch from the bend, and the SO-239 is attached using stainless steel or brass hardware*. Two small holes are drilled in the lip and the plate is mounted to the copper TEE with #6 s.s. self taping screws*. Solder a ring lug* to the center conductor of a 11" piece of RG8 insides* and screw it into the threaded coupling* on the SO-239 *(center wire and plastic dielectric only- remove and discard shield and outer covering). Slip the RG8 insides into the 3/8" copper tube* 4-1/2", and tap the copper tube to the radiating element 3-1/2” from the SO-239 center, with a copper strap bracket *.

The tap on the Gamma sets the impedance presented to the feedline. Resonance (center frequency) is designed into the measurements.

Have fun on 2. 

Geo>K0FF

* denotes kit items see: http://homepages.dstream.net/K0FF/ForSaleStuff/HaloPartsKit.DOC

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