Cal & Swr readings with Antenna warning light

A choke doesn't "choke" the signal on the inside of the coax. The guy at Bell's may be confusing the idea of making a balun to keep stray signals off the *outside* of the coax when you use your unbalanced coax to feed a *balanced* antenna (meaning both sides are identical, i.e., a dipole). A typical mobile whip is unbalanced, and when tuned properly is resonant and transfers all the energy put in at one end out through the other. F'r instance, when transmitting, it goes out the panel jack on the rear of the antenna, goes out the center connector of the coax, and to the hot element of the antenna, and out to the world. On receive, the opposite happens.
When an antenna is tuned, there is *absolutely* no effect to the signal by the length or shape of the coax run. If changing your coax length makes a difference, then your antenna is not tuned correctly, and the coax is coming into play as part of the matching network.
And, as in my last post with the diagram, the mount has to be correctly installed. If it fails the ohmmeter test, it will fail the RF ("radio frequency") test. If you don't have continuity on your ohmmeter from the center coax pin at the radio end to the stud at the mount, and an open circuit from the stuf to the ground (or center pin of the coax to its shell), your feedline is either shorted or open, and nothing you do above the stud will fix it.
As for ground bonding, the short braid from the door to the body below the "'A-pillar" to bypass the hinge will work best. The longer a ground wire is, the more it seems to act like part of the "hidden half" of the antenna. And the more surface area the grounds have (like braid), the better they'll conduct RF.
RF is way more critical than DC; but if the DC isn't right, the system is doomed for failure.
So, before you spend any more $$ -- how's your mount and coax check out with your ohmmeter?
HTH,
-- Handlebar --

 

That fiberglass antenna has a certain amount of wire wrapped around it. This is what is needed +/- a 1/4 inch or so, for a proper tune of the antenna. Adding the 6 inch spring is going to add to the tuning length of the antenna unless the spring setup is insulated from the antenna system. But they are not. You are going to have to trim close to 6 inches off the wire wrapped around the fiberglass of the antenna if you want to keep the spring.

Your best bet is to dump the spring and go with a whip style antenna. They handle abuse much better.

Oh as far as magnetic mount antennas. They work just fine. I have a few vehicles that I am using mag mounts with wilson 2000 whip type antennas and they work wonderful. I am running much hotter radios then you peaked and tuned cobra and I have absolutely no issues with my mag mounts on my personal vehicles. They give me the option of being abole to easily pull them down if the need arises such as low garage doors or putting my vehicles on hoists in shops with lower ceilings. Heck I have one on the top of my 98 dodge quad cab 1500 4x4 and I have hit trees with the lower section of my antenna and the magmount let it tip back without doing damage to the antenna. It was a pretty good hit because I have had this antenna stay up at speeds of 100mph in heavy wind.

I get an easy 15 miles of range with my mag mounts and have swr around 1.5.