Hello,

On 2m/70cm some antennas work better when you use a mag mount (Sirio HP2070
for example) because they are tuned to be used with a mag mount: added
parasitic capacity between bottom of the mount and the car's steel. Expected
you do not drive a 'vette or an Audi...

For lower frequencies it's better to drill holes or to properly ground the
antenna to the car, as most mag mounts are not wider than a sq foot and you
would quickly be annoyed by the potential differencies between the car's
ground and the antenna ground, resulting in HF re-entry problems as your
antenna will be then antenna + coax cable and all the hassles of bad and/or
variable SWR.

73 de F8BOE Olivier ...-.-