That is the antenna that i used for a while. After a while i got sick of it and modified it. You can get a cb replacement antenna and cut it to the lenght you need till you get a discone.
Check this out:http://www.liveatc.net/forum/download.php?id=96
That is the antenna that you have, with a different whip cut to the length needed for 126.55 mounted on a pizza pan. You need to have it on somekind of pan/plate/vehicle/.... with a steel base, thats what the magnet mount base requires for anykind of reception at all.
If anybody needs an antenna calculator here is one. A 5/8 wave antenna will almost always give you the best reception, learned taht from reading and experience.