using a common mode choke in some form in a mobile install is a must as far as im concerned.
you will always have common mode currents on your feedline in a mobile unless you drive an all aluminum flying saucer with the antenna right in the middle.
in base installs, many choose the coax wrapping method, but it's a bit bulky for mobiles.
there is also a caveat to using the coax coiling method.
you have to trust that you haven't inadvertently created a reactive choke instead of a resistive choke if you don't own the test equipment required to test your choke once you made it.
it's not as much of an issue when you only use CB since it's only one band, but can still cause problems if your coil isn't made correctly.
for moblies, about 18 inches worth of ferrite beads right at the feedpoint of the antenna is a better solution. mix 43 and 31 are good choices, and im sure there are others that will work.
of course it's not as fun to build by a long shot LOL.
one thing to NOT do is to buy a cheap set of snap on ferrites from amazon and hope they work. most likely their purpose has nothing to do with HF frequencies and they may be almost entirely ineffective.
here is a kit you can buy for pretty cheap that will do the job well.
https://www.ebay.com/itm/Palomar-En...hash=item2ceb82cd39:m:m-wJ51yopcNoX6gN5D7Vzfg
you can probably buy chokes cheaper if you go to amidon directly, but you need to know what you are looking for.
hope this helps.
LC
