I tried building this diy 2m antenna
, and I must say it worked almost perfectly from the beginning.
However, there are some additions I feel the need to put here.
For starters, soldering a wire to the center of the UHF connector requires a powerful soldering iron.
Second, even if you do manage to solder everything correctly, cheap UHF connectors seem to be made of sintered powdered metal. This means that under wind, or in my case, under the stress of bumping it into the windowframe as I repeatedy hung it out the window every day, the connector shattered below the solder joint.
1. coat the connector in hot glue.
2.cut a coke bottle in half, make a hole through the center of the plastic cap, and slide the top half down over the main radiator.
3.use hot glue to seal the main radiator through the bottle cap, and anchor the bottle half to the radials.
It works well for the local 2m repeater, but after borrowing an antenna analyser, i had to bend the radials down very much to get a 55 ohm impedance, which is weird.