yes you should add a choke to the feedpoint of the antenna, and no you should not use the "wrap coax around a form" method.
go on ebay, and look for a place called palomar engineers.
they sell snap on ferrite chokes that are made for this purpose and they work better than the coax method. they are also WAY less bulky and obtrusive.
the kit comes with 5 or 6 chokes and you just snap them on the coax right at the feedpoint.
now, as for the larger point of "should mobile installations use feedpoint chokes?"
the answer is a resounding YES!
in a mobile installation the vehicle body acts as the counterpoise to your antenna, and as is pretty obvious, no vehicle makes a perfect counterpoise.
putting the chokes on the coax at the feedpoint of the antenna will force those currents that are swirling around on the shield off of the coax shield and back out to the antenna and vehicle body.
I put those chokes on every mobile setup i do, and have ever since reading this:
and this:
LC
