I know of several here that have used Tune Trapper hidden antennas, but I tried it and it was not all that great in my application.
I ended up with a powered Biketronics Hogtenna.
Before installation, I did a radio scan and in my garage received 22 stations that would come in. It's been quite some time, about 5 years since I installed my Hogtenna, but as I remember after installation the scan brought up 17 or 18 stations.
This worked very well for me and still does, I just don't listen much to radio anymore since I installed my iPod module.
I mounted mine up under the top of the front non-removable portion of my fairing with double stick tape and never looked back.
Good luck with your choice.
P.S.
I just saw Jerry's reply; he beat me to the Post button.
Just an update on rural areas prior to my iPod module installation, my Hogtenna worked very well out away from the city. I've been at least 150 miles from the big cities and still got good reception. Jerry is right, a "real" antenna tuned to the FM frequency is the best, but in the process of my installation I did try the Tune Trapper and also several other non and powered hidden antennas and the Biketronics Hogtenna was by far the best, in my application and opinion. Your setup may be different just like the Tune Trapper didn't work well or me, the Hogtenna may not be best for you.
Again, good luck.