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144 MHz Halo Antenna | Radioaficion Ham Radio

144 MHz Halo Antenna

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144 MHz Halo AntennaA 144 MHz Halo

This halo antenna was built to have an omnidirectional coverage while working in VHF contests. The idea was to have a small but useful antenna for receiving, but it has demonstrated very capable on TX also.

Construction

To construct the antenna, the first thing you need is a cooper or aluminum rod 1 meter long. Cut it at 98.5 cm and round it until you get a 3 - 4cm gap. Your antenna is done. Now you need to connect it to the coaxial cable and make the appropriate matching network, in this case a Gamma match. Connect the braid of the coaxial cable to the center of the rounded dipole and solder a 22, 33 or 47 pF trimmer to the center conductor. Now connect the other side of the trimmer to the center of the dipole arm with a small cooper wire or similar

Now you have finished the electrical antenna, but you need to make some mounting hardware to make the antenna usable. I made a PVC skeleton to support the antenna and, at the same time, to mount it over a magnetic mobile mounting. You can do in this way or in any other useful way to you.

I glue together some pieces of PVC to make the skeleton. I also glued a PL-239 socket  at the skeleton bottom end. See the images for details.

Here you can see how the PL-239 plug is glued into the PVC:

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