I'm truly lost

The first thing is you need to use an external SWR meter, the internal SWR meters in the radio generally are very unreliable. The second thing is to run a good quality coax to a single antenna. The coax in the trucks are usually a cheap coax that the factory uses. The third problem with the SWR readings changing on you is because of a lack of an RF ground. There's a lot of info on this site about RF bonding. Basically it's adding flat cables to the trucks body to help with the lacking RF ground that these new trucks need, in order for the antenna to perform properly.

 

"...run a good quality coax to a single antenna..."

Words of wisdom

 

OK I am not going to get too technical on this but this is what is called a Common Mode Current, where the coax acts like part of the antenna and when you grab the coax, it added capacitance to the system and changes the SWR.

So here is what I am going to suggest, first order some grounding straps and good coax, DX Engineering is a good place for all of this.

Buy good coax, you don't need a lot, if you have time, do it right, get some clothesline to feed it through where the coax will go to measure out how many feet you need, add a few more, and order it with the ends — even crimp-on ends will work if they are commercially made.

I do not have a recommendation for a mount but it would be a good idea to look at replacing the factory mount.

Whatever you do, don't rip up the factory system out of the truck, the am/fm/XM radio may all use it, it is called a multiplexed system.

After you have the supplies, come back here and search for grounding ideas or get ahold of Craig and/or Night. Follow their instructions.

 

Don't remember what they call that box but it has your am/fm antenna and cb radio running through it. You have run separate coax from your cb to the antenna's to solve your problem's.

 

I was always told to use 18 ft of coax it’s never let me down ..

 

If it was me I wouldn't touch anything and run a separate cable up and over the driver's side door and down behind the refrigerator and out through the floor underneath the bunk and under the cab and up the back of the cab on the inside of the fairing and make a metal bracket to attach to the spot where the upper and lower half of the fairing come together and you can use the factory bolts and put a little 3-in ground strap from the metal bracket that you made to the metal bracket that holds the fairing halves together and put the antenna outside the fairing and you should be golden.

 

Your right, I forgot that jdchet mentioned on another thread that the Volvos were actually metal instead of fiberglass. It would be nice to use an antenna analyzer to get the full picture of your antenna system. But once you install new coax to a single antenna, I'm sure your problems will go away.