Dennis H
If you don't have a camper to interfere with the placement the center of the roof gives the most symmetrical signal and the easiest match.

allure45connie
All things being equal the mount on the roof as it will be higher and less obstucted . It will also have a more uniform pattern of reception the more centered on the vehicle it it .

bandaidgirl
When i drove my big rig it was mounted on the mirror. But they are built-in that way(the hook-up...not the radio. I purchased the CB). I had a $30 walmart radio and people thought it was a high-dollar one....always wanted to know where i got it and how much it cost. They were surprised. Maybe it was in the connection...i dont know.

Jalissa
what do you mean.

stygianwolfe
either one will work well if you connect it well.Most magnet antennaes are only good for about five miles.The signal starts to fade after a few miles,but can be picked up by other radios to be audible if they adjust the squelch on their radio.Mirror mounted antennaes get a better ground on the vehicle and handle larger power radios and help keep the signal from degrading,and also keep the power to transmit out a little better.As far as recieving,both will pick up very good.It just depends on what you want to use the radio for and what kind of equipment/power you want to run