High SWR on new install

[ipfd320]

It Would be Really Helpful if you (the op)--can Snap a Few Close Up Pics of the Antenna Mount--the Antenna Base and Antenna Tip so we can Actually figure Out How to Answer This

Using the Fire Ring You Have to Make Sure the Nylon Washer and Nylon Fire Ring are faceing the Right Direction

I Left the Firestick Site in Post 5--Have you Gone Thru the Tech Areas???--They are Very Informative

There is an area about Using the Wrong Antenna--(Ground Plane vs Non Ground Plane)

IDENTIFYING FIRESTIK


Do Not Cut the Connector off the Fire Ring--This is Matched for the for the Fire Ring for Electrically Length

 

[atech]

Is your rear door fiber glass or metal? No ground plane if its fiber glass !!

 

[guyonearth]

Is your rear door fiber glass or metal? No ground plane if its fiber glass !!

This kind of mount attaches to the inside of the door frame, not the door.

 

[Ravenkeeper]

I use to own a '03 Grand Cherokee, and the back door is metal.

FireStik "troubleshooting for high SWR":
- Is the mount bracket grounded?
- Is the antenna and cable assembled correctly on the mount bracket? (With my high SWR, this was the case)
- Get a taller antenna. FS says that you want at least 50% of the whip above the vehicle, when mounted like this.

Personally, I would get a taller antenna, that looks like a 3', I'd get either a 4' or 5'.

 

[mmckenna]

I installed a CB radio system in my Grand Cherokee and I'm getting high SWR readings, roughly 2.2 on channel 1 and 40.

OK, 2.2:1 SWR on channel 1 and 40, but what is the SWR on channel 19? Higher on channel 1 and 40 but low in the middle just means that the antenna has a very narrow bandwidth.
If it's pretty flat across all 40 channels, then there may be an issue.

I’ve read a variety of opinions regarding coax length and there doesn’t seem to be any concrete evidence to support a full 18 feet versus trimmed to the proper length

Use only the amount of cable you need to run from the radio to the antenna. The claims of "18 feet" are BS as it doesn't take into account the velocity of propagation of the cable. A properly installed and tuned antenna should not rely on specific cable length to give you low SWR.

Containment: I’ve been checking SWR in an open area...

An important point that many overlook.

...using the built in SWR meter.

Don't put all your faith on the built in meter. Check it against a known good meter. See if you can find someone local that has one, or invest in a separate meter if you are serious about this.

With antenna cap installed I calibrate then check SWR on channels 1 then 40 then adjust.

OK, but check on channel 19 also to develop a curve. Checking on the two ends doesn't give you all the info you need.

I’ve checked the coax for shorts and none exist.

Have you checked for opens?

I installed an additional wire from the mount to the chassis to make sure I’m getting good ground.

From the chassis or the body? DC ground and RF grounds are not the same. Use a short conductor from the mount to the vehicle body. Make sure you are getting a good connection. Scrape off paint if needed.

Side note: I made contact with someone 30 miles away and they reported a strong signal. It’s probably not relevant, but I was surprised and figured I’d mention it.

To me, that sounds pretty good, and makes me thing that maybe the built in SWR meter isn't as reliable as you'd expect it to be. Until you check all this against a known good meter, take the results of the built in meter with a grain of salt.

30 miles with a strong signal is pretty good for a stock(?) CB radio with a short antenna.

 

[kf6irk]

I agree that all the heavy metal gear on your roof rack is causing your issue.

 

[ClemsonSCJ]

Hey man you may have already gotten it figured out but in case you haven’t...I have pretty much the same setup. Cobra radio, K40 3’ fiberglass antenna. I have a 2009 Grand Cherokee with that same mount and location and I had the exact same issue. What I found was that the mount didn’t have a good ground at all. So I ran a grounding wire from one of the mounting screws to the nearest quality ground I could get and my SWR went down to where it should be. Hope this helps.