My van is an 2006 with fiberglass topper. As such I did not want to attempt an antenna mount on the roof.
There were a couple posts on wrangler forums about replacing the AM/FM antenna and using a box to adapt the CB antenna and AM/FM wires together without interference.
If you are a true CB Radio guy, stop reading now, because you are likely frustrated already.
I took on the challenge to do this on an Econoline van and it turned out sooo simple and effective enough for my liking.
FireStik Antenna (3ft) https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
IMCB - ProComm Inverse Multiplexor System
316 Stainless Steel 1/4"-20 male to 3/8"-24 thread adapter
1/4"-20 Tap/oil of your choice.
Start by unscrewing the stock AM/FM antenna. An adjustable wrench will go a long way on this project. The stock antenna thread pattern on my van was 10-24.
You will notice that the threads don't start until about 3/4" down in the hole on the base mount. There is an outer plastic protective ring, with the internal metal sleeve that the stock antenna rests in.
Take the tap, and thread the metal sleeve down to the stock threads. No drilling is needed to insert and apply the tap.
Optional, but you may want to add locktite to the threads of the thread adapter.
Insert the thread adapter male end into the newly created threads inside the stock radio base. Make sure the thread adapter is sitting flush! If you did not tap all the way to the threads, you may need to grind off a thread or two of the adapter (shorten it). I ordered multiple adapters not knowing how I wanted the final product.
Insert the Firestik into the female end of the thread adapter (again optional, but you may wish to add a spring).
Here is the final completed project. The CB antenna on left and am/fm on right.
You could potentially find a 10-24 thread adapter that is long enough to reach the stock mount, OR use an aftermarket radio male-male adapter and then use a female-female adapter for the firestick without having to tap the hole.
On the inside, you now need to hook up the wires to the multiplexor. This is sooo easy! Adapters are included to go from BNC to the radio antenna, as well as PL259 for the CB antenna. Follow the included directions for which wire goes where... it is fool proof.
Once you are done with that, I do suggest tuning your SWR with the end of the Firestik as intended. I used a 12ft cable between the CB and multiplexor, guessing that the radio antenna wire was about 6ft long (you want 18ft).
I've not had a chance to test this on the interstate yet, but in my Louisville, Kentucky, dense tree/home neighborhood, I am getting 1/2-3/4 mile range with SWR between 10-11. This is more than enough for my use case.
Overall my goal of being able to use the CB short range with a non-invasive/stealthy antenna install was met. There was no compromise in FM radio reception, in fact it reduced static.
Potential other changes to improve range would include running a coax cable from the multiplexor to the radio antenna or getting a longer antenna. I would not recommend a longer antenna on the stock radio mount without a spring if not at all.