Originally Posted by Merlin

IIRC, duals require a splitter (cophased harness) and different coax than a single ant. (i.e., resistance is different, you shouldn't just use your existing coax). i think it's something like 75 ohm vs. 50 ohm or something to that effect, you may want to double-check on that one.

duals can also be trickier to tune, and have a more directional radiation pattern.

spacing is also more critical with duals, i believe either 1/4 or 1/2 wave spacing is ideal. not many vehicles are 102" or 204" wide, if you're going to run them mirror-mounted. you could run them front-rear, but that type of a backdoor setup has inherent problems of it's own. maybe good for keydowns or other directional uses, but not the best for a daily driver or trail rig.

in *most* (but not all) cases, you may have better results with a single ant. mounted to the center of your roof, or even to your toolbox. plus, they're easier to install, easier to tune, not as flashy (not so tempting to theives).

if you mag mount it as some have done, it's easy to take down for parking garages, drive-thrus, etc...

just my .02. YMMV.