I was always told that cb antennas are tuned from the factory using an 18' coax (if they are non-tuneable models). The cab will block the signal a bit. Not having a 'clean power source' hurts alot of folks. They end up with alternator noise and have to add in so much squelch to quiet it down that they can't pick up a decent signal. Our local cb guy (who is a semi-quadriplegic by the way) has always told me that mounting it as close to the center of the vehicle is best. If it's at one end or the other, it will not pick up/transmit signals as good.