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  Antennas for 2 meters

and up

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      The Halo is horizontally polarized and almost omnidirectional, wind loading is low and it's light weight makes it ideal for portable use.

      This particular one has no gamma match, rather, the mounting is used as a closed stub match, it has very wide bandwidth, which, coupled with simple construction, means it is easy to make and forgiving of a few errors during manufacture.

       It's a good idea to cut the material a bit long at first, then use clamps to make a prototype that can be adjusted until it works satisfactorily before final cutting and bolting.

       If you are mounting the antenna the same way I did on 25 mm square tube, add 25 mm to the length of the stub to allow for the diameter of the mast.

      Varying the length of the stub is easy to do with a clamp, slide the feedpoints along the stub for minimum SWR, it will usually be at the open end of the stub for 50 ohms, if you are stacking two, slide the feedpoint in until you get 100 ohms. This results in 50 ohms at the junction of the feedlines, two 100 ohms in parallel = 50 ohms, An analyzer makes this easy but it can be done with just a SWR meter.

      As usual, always use a choke balun near the feedpoint, you will get more consistent and reliable results when testing and less RF on the feedline, pattern is better also.

      So far this antenna has proven to be very useful for weak signal work, you need to hear in directions that the beam is not pointing, when you know something is there, you can search with the beam.

A simple Halo for 2 Meters

The two Sark plots at right are of the actual antenna shown in the pictures, note that, while the antenna is optimized for the lower end of the band, it is usable over the entire band.