This is the best omnidirectional 2 Meter antenna I have ever encountered.

The highest cone is to form the lower half of a half wave vertical element.

The lower cone is a decoupling sleeve for the antenna mast.

If you find one of these at a hamfest for $20, buy it. It works great, and a lot of people do not know what they are. You could actually build one from aluminum flashing and a mag mount. The original manufacturer is out of business and the Isopole is no longer available new.

I have uploaded photos of the restoration work on mine, and the data sheets are provided here for you to do your own work, should you be lucky enough to find one of these.

Click on the images below to enlarge: