CH Mack and high SWR

Are the trucks made form fiberglass?

Are the antennas properly grounded?

 

Sounds as if the truck doesn't have enough metal on it to serve as a ground plane. You may want to look into an antenna that doesn't require a ground plane.

 

I'm in a mack pinnacle. On the mirror mount I put on I filed down the paint their works good now.

 

Ground is a problem, if you're sure you have a good ground. Did you remove the factory antenna it can interfere with good SWR even if its disconnected. If you've shut coax in door jamb you may want to try new and route another way. If all else fails find a new location... on day cabs the upper rear grab bar works well.

 

Your setup works great in a 'Binder' which I assume is an International truck but the SWR reading is through the roof in a Mack truck. What is different is the truck itself. An antenna ground plane problem is suspected when the SWR reading is 3.0 or higher and/or you cannot get the SWR reading to lower by tuning the antenna. In order for a CB radio to work well with a low SWR, the truck itself must provide a large enough antenna ground plane. I am not talking about an electrical ground. What I am talking about is the antenna ground plane. A totally different subject.
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By using ground straps or large gauge wire, you can interconnect the large metal components of the truck together to create a large antenna ground plane. The length of the straps or wire is intentionally kept short. For example: you connect the door to the cab by running a ground strap to the bolts that mount the door to the cab by way of the hinge. It will look like you are shorting around the hinge. Then run a separate short strap from the bottom of the cab to the chassis frame.
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.Do NOT use long lengths of straps or wire as they will work like another antenna. Therefore, do not run a strap from the door directly to the chassis frame or battery.

 

The above problem makes it impossible to "slip-seat" and have a decent working radio

 

Could you post an image of the door and mirror on the Mack truck and something closer up so I can see how you are mounting the antenna on the mack. And are you wanting to use dedicated antennas on each Mack or switching the same antenna around. I may be able to help you with this as I have some exp. with correcting these issues..

 

I'm also having the same issue with My Mack Pinnicle day cab grounding with High Swr's. It came with stock duel antenna's and installed coaxle duel cable. when I first got in the truck all I did was hook up my cb and everything seemed fine, I never really checked the swr's but the radio seemed to work fine so I just went with it. about a year later my connex radio stopped working I think I blew a final so I purchased a cobra 29 classic which has a antenna button that lights up red indicating you may have an antenna issue so I purchased a swr meter even though the radio has one built in and My swr's were through the roof (In the red).
My first though was it's not grounding properly so I purchased a 14 gage wire and grounded it from under the antenna to the nut that holds the mirror to the door but that didn't do much good. I tried to hook up My Wilson little wil to the roof of the cab but still getting really high swr's, hmmm that's weird? The weird thing is when I keep the passenger door open my swr's are nice and low but as soon as you shut the door the swr's go back up into the red. Why is this I wonder? From what I have read here Mack Trucks seem to have a grounding issue so My guess is I need to ground the truck. can anyone give me any tips on how to exactly ground it and if I'm using duel antenna's do I need to ground both?
It also seems to be an issue the bracket that holds the mirror to the door is not made of metal so the bar is not grounded to the chassy properly making the antenna's swr's go way to high.
Should I ground from antenna mount to the door where mirror meets then from door hinge to chassy hinge then chassy to frame? I'm confused as hell and my radio sounds like crap.
I was also thinking that maybe the antenna on the passenger side may need to be replaced because I have hit a lot of tree branches over the year and it seems to be an issue on that side only. why would the swr's go down with the passenger side door open but not when it's closed? it don't do that on the drivers side? I'm confused... help please