Magnetic mount grounding

[Glorfendill]

OK, I've just tossed a small chunk of change down on a new antenna, and magnetic mount w/coax to get my old CB back up and running again. After doing a bit more research than I had ever done on CBs/Antenna's I've learned that there are GP and NGP antenna's and low and behold mine is a GP as most are. Now, during part of my research I run into this little tidbit of information and I just wanted to run it by some of you guys and find out if I'm understanding it properly.
"Magnet mounts rely on high resistance, capacitance grounding. If you use power amplification, there is a good chance that heat will discolor the vehicles paint. We do not recommend the use of amplifiers with any magnet-mounted antenna"
Now, my understanding of that is saying that Magnetic mounts are actually grounded via a capacitor through base of the mount and the paint of the vehicle to the metal surface of where it is mounted. So my GP antenna is by nature of the magnetic mount, already grounded.

[HI-TECH]

yes it is grounded but with all GP antennas you need to have a much larger ground than just the base of the magnet. when your transmitting the RF energy goes though the base onto you car, RF energy is just that energy, when when using a magnet mount there is some resistance between the magnet and the car body, and with any resistance it will cause heat, witch causes your paint to become discolored

[Glorfendill]

Well then, does anyone have any suggestions on what I should use to properly ground it?

[Phaze91460]

Ground your radio chassis to the body of the car. Your coax is grounding to the radio chassis, etc. Mag mounts are not going to directly gournd because good paint does not conduct electricity.

What kind of antenna, radio, amp etc. are you running ?

[Glorfendill]

OK, I have a Cobra Sound Tracker, 29 LTD ST Model; a Truck-spec 5" Magnet Mount with 12' Coax TS-401; a Firestik II FS4 Antenna; No Amp; and just a standard cobra microphone.

The firestik antenna says I should use 18' of Coax. Currently I'm running on 12'. The Cobra Radio as a SWR Calibration feature that when I use it I keep coming up low (The needle won't go all the way to the Cal mark on the display even with the SWR Cal dial all the way up.) and I'm not sure if this is because the antenna is isn't properly Grounded, or if the missing 6' of coax can cause that, or some combination of the two.

You advise I ground the radio Chassis to the Truck, So just a 14 gage wire from a mounting screw on the radio run out to the vehicle ground?

Also, I'm curious if I will get a signal difference from mounting the antenna towards the rear of the roof where the metal is more stable, or towards the middle and center the antenna for a better reflective area?

[oknaz]

Mine is on my tool box of my truck and it's bolted to the bed rail's .

[Phaze91460]

Yes on the grounding. Give it a try on the mounting location. I am finding out just how important what kind of antenna you use and how it mounts is. Will post more on that later. And find yourself a meter to hook in line and check your SWR because it sounds like something is wrong with the radios function.

[animal13]

My buddie has a cobra 29 wx nx that the swr wont go up to the 1:1 mark the dial wont move enough although i am not sure about with an swr meter just what the one on the cb says