But I will put in my caveat here with regards to mag mounts. They are unsafe, and just so full disclosure is always attempted, I will put up some info as to why.
Now I know that several folks do use them, and they have not proven to be a problem, but everyone needs to heed this warning from Alan (KØBG
) website which is very well read and respected in the Amateur community as well as others:
I've placed mag mounts first for a good reason; they're not safe! The one shown in the left photo is a typical unit. When they're demonstrated in retail outlets, they're stuck to a thick chunk of metal. Since the amount of force is reliant on the thickness of the material it is stuck to, the actual force will be much less when it's sitting atop your vehicle. And it doesn't make much difference how many magnets they have, or how big they are. The fact remains they will become flying missiles in the event of a crash. There has been one confirmed death, and possibly a second, caused by a mag mount dislodging in a crash. Distractors say that's good odds, but it isn't. If you haven't already, read my Insurance article.
At a hamfest I attended, I ask the owner why his three magnet mount was tied down with a couple of bungie cords. He said he tied it down after it came off while he was on the interstate. Aren't you glad you weren't behind him?
There is another problem with them; they increase ground losses. If you've read my Antenna Efficiency article, you'll know why minimizing ground loss is so important. If you think attaching a ground strap to the nearest hard point on your vehicle will help negate this situation, you're wrong! By the way, it doesn't make any difference how many magnets they have, they're still lossier than direct mounting.
There are two more problems users should be aware of. First, they collect road debris (mainly metallic brake dust) which eventually gets between the magnet and the sheet metal. Secondly, the base cover, usually a rubberized plastic, has an affinity for clear coat vehicle finishes. It is a given that the surface under the mag mount will become both scratched and/or discolored over time. In some cases, less than a week!
The bottom line is, if you have to resort to a mag mount for your antenna, you haven't thought long enough about other, safer, more efficient, mounting techniques.