Hey gang,

I'm having issues with my CB install. I purchased a Midland 75-822 CB and had it working for a few days, and was able to talk to others, but today, the CB died. I was listening on a channel, had a lot of squeel and tried changing the channel, when the CB just died and went blank.

I got a hold of a SWR meter and hooked it up with a friends CB (also a Midland). The SWR meter was showing over a 3.

Here is the setup I have:

I have installed a 3' firestick on my JK. I used a rugged ridge spare tire mount. Here is the mount, it looks very similar to the teraflex mount, I think:


On the mount is a Firestik K4-A stud mount:


I ran PL259 antenna cable to the center console.

Here is a picture of the stud on the mount. Sorry for the poor quality but does it look like I have the order correct? The nylon washer right on top of the mount.



So, after a lot of research on this forum I see that many recommend grounding the mount. The Firestik website also talks about how the mounts should be grounded.

I ran a 14 ga ground wire from the tailgate mount to one of the subwoofer bolts. Here is the one I used:


I hooked the SWR meter up to a friends CB again and the ratio dropped to 2.5. While it's out the red zone on the meter, I still recognize that I probably need to get it lower.

Ultimately, I have two questions.
1 - Is it likely that the high SWR I had fried my CB?
2 - What am I doing wrong with this SWR? Any recommendations?

Thanks so much for your time!

 

If you did a lot of transmitting with that high of a SWR you may have fried it. Could be that it just died also. Electronics seem to die fairly quick if they have a problem.

 

Yeah, it was strange. Anyway, does your setup differ much from mine? Any tips on getting the SWR down?

 

High SWR is a radio killer!

Tailgate / spare tire mounts are tuff to ground and is why you experience high SWR.

Proper install of the stud mount:




h t t p://www.firestik.com/Tech_Docs.htm

 

Thank you - looks like I have the stud mounted properly.

I see a ton of people rolling around with tailgate mounts. Surely they have gotten their SWR down from a safe level. It's killing me as to why mine is so high.

Is there a better grounding spot someone would recommend?

 

I had high SWR on my firestick. Much higher on 40 than 1, which means electrically long but the adjustable tip was all the way down.
I ended up taking the plastic tip completely off and all my readings are below 1 across the scale.
Good luck

 

Ok, I picked up the rugged ridge mount as well, and there were a few things I had to do to get my SWR nice and low.

From what you've shown, you have the antenna mounted properly, but your bonding needs some work. Side note: bonding versus grounding, short version. Grounding is what you do to make sure DC current can get back to the battery. Bonding is what you do to connect the various parts of your vehicle into what's effectively a single unit for RF purposes.

Take some sandpaper and sand down to bare metal the areas on your mount I've marked in red:

You only need to do it on that one side in those two spots. Just make sure that the antenna stud and the washer makes good contact with the bracket.

If you're lucky, that should do the trick. I'm not running any bonding/grounding straps, and my SWR ranges from 1.2 to 1.5.

If you're not lucky, then you might need to bond your tailgate to your body. While you can get a passable bond with the 14 gauge wire you're currently using, RF signal travels better over a wide surface than through a thick wire. So a braided strap would make a much better bond. Also, you want to keep the strap as short as possible. If you run it from that bolt on your tub all the way to the antenna mount, it might act more like another antenna than a ground plane, which will drive you nuts when trying to tune your SWR. Best to try and keep the strap less than 18", preferably less than 12". Unfortunately, that means drilling a couple of holes to mount the strap to.

If you want more info on bonding and how to do it right, ask a ham guy, but be prepared for a long conversation. Or cheat and read up on a few web sites like this one: http://www.k0bg.com/bonding.html Just keep in mind that you're only dealing with CB, so you don't have to go anywhere near as far as what the ham guys do for their vehicles.

 

Thanks for the detailed reply. I sanded the mount down in the two locations you showed (down to bare metal) but no success. It only dropped my SWR from 2.5 range to 2.25.

 

Get a ohm-meter and see what the resistance is between the bottom part of the antenna stud and the stainless bolt that's in the hole you sanded. It should read zero or very nearly that. If it isn't, you probably need to do a little more sanding.

Next, measure the resistance from the bottom part of the antenna stud to the stainless bolt that's in the hole that still has the paint. It should read about the same, as it's getting it's connection through the skin of the tailgate door. This test is just to make sure that the bolt that you did sand the hole for is making a good electrical connection to the door.

If both of those read close to zero, then chances are you'll need to install a strap to bond the tailgate door to the tub. But just to make sure, I've a few questions:
Are you testing the SWR with the tailgate closed and the spare tire mounted? Those will mess with your readings, so you want things set up as they'll normally be on the trail.
Are you testing the SWR with the cap on the antenna? Your SWR will be different when it's installed.
Are you testing your SWR near a building or tall fence? If you're too close to a structure, your SWR reading will be off. From what I recall, best is at least a full wavelength (40 feet) away, but you should be at least as far away as the length of your antenna. The Firestik II tuneable tip antennas are 5/8 wave, so that means you should be no less than 25 feet away from a structure.
Are you using a high-quality cable with molded-in connectors? A cheap cable might work fine for a bit, but it also is likely to fail much sooner than a heavy-duty cable. And crimp-on connectors tend not to fare too well when exposed to the elements. You don't have to worry much about UV exposure, but road grime, even if you don't live up north or on the coast, can cause some pretty nasty corrosion.

Good luck chasing this down!