yeah, that antenna is going to limit your transmitting range to just a couple of miles at best i believe. it is a really good one for the trails where your group is fairly close together, but kinda sucks for on the road or highway. just not good enough.
actually, the antenna is the most important part of a cb system. all the radios are limited to 4 watts out by the FCC. the only thing you can do to get the most out of those 4 watts is to get a really good antenna, and then have it tuned.
the longer the antenna the better usually. and mounted close to the center of the vehicle is best, but it does need to extend at least a couple of feet above the cab for the best performance. and for most antennas over 4 ft tall, a spring is usually needed.
i'd try craig's list or ebay for a really good antenna for a decent price. K-40, Firestik, etc. and you can still get magnetic ones that are really good. you might opt to get just the magnetic mount that has a 3/8x24 thread mount, then get a really good antenna that has that 3/8x24 mounting stud. that way it will be easily removed from the magnetic base when going thru the car wash, into the garage, theft prevention, etc.
just my $.02.