I have been using a rollup J-Pole antenna on my bicyle and it has been
working very well. With 5 watts, I am able to get 50-60 miles range
into
the local repeaters. I built my rollup J-Pole out of 300ohm twin lead
that
I bought at Wally's World. I used electrical tape to secure it onto a
fiberglass
bicycle antenna that I also got there. Below is a picture of the
antenna's
feed point. There are other
pictures here.
Here's the feed point, click to see
the bigger picture.
The program that I used is jpole.exe.
Download it and run it under windoze to get output similar to the
following.
This is the information for building an antenna resonant on 144.390mhz,
the APRS frequency used throughout the U.S.