Please help a dummy understanding bonding

[Guardsman]

I have a 2013 Honda Accord 4 door with one of those 2" pucks made by Jerry mounted on the trunk with a Predator 10K antenna connected to a Galaxy DX 959. SWR is above 3 across the board. Know I need to ground the antenna but not sure how. Previous attempts have failed.

1. Closest ground point I can find is 2 bolts under the back seat which would make the ground runs about 6 feet so I can fully open the trunk. Is a ground that long even worth the effort? Unfortunately the trunk hinges done have bolts to connect the hinges to the frame.

1a. If you look at Jerrys product number 607, that is what I have mounted. You can see the hole for the set screw on the bottom of the puck. Would the ground wire go between the top of that piece and the bottom of the inside trunk lid or should I just screw it onto the very bottom of the puck?

2. Will probably need to bond as much of the car as possible due to almost no metal in entire car. If the 6 foot ground from antenna base to screws behind back seat help, where should I begins bonding next? For example, I read to bond the door frames is something similar. So would those grounds go from screws in under back seat to doors? In other words, do all the ground runs have to connect to each other?

3. Not knowing all the ground points in my car, would a service guide book explain or show where they all are?

Please help. I'm so lost. Thanks!!

[ Post made via iPhone ] [ external image ]

[MDYoungblood]

A SWR of 3 across the band sounds more like a short either in the installation of the mount or the coax, I'd check that first. Now bonding is a big issue, first things to do would be the hood and trunk lid or hatchback, you should see a SWR improvement in doing those. It never hurts to do the doors as well. I also like to ground the radio's case, the negative lead ready isn't a sufficient ground, a wire from a case screw to a good ground point, seat bolt, metal under dash, steering column, etc. If the mount is installed properly it should be grounded on the mounting bolts.
Next thing is most antennas are made long, reason is the manufacturer doesn't know what your install is so it's easier to shorten one then buying another longer whip. So you may have to do some trimming.

3's

Greg

[PA629]

Simplest way to explain bonding is to run a wide flat braid across any hinge on the vehicle, i.e. doors, hood, trunk lid. Then run a similar flat braid from the tailpipe to the frame. This should cover 90% of the bonding needed.

[Scipio Kid]

I'm no expert but I'll readily agree with Greg on this one. If you're getting SWR that high, there may be another problem. I've done dozens of mobile installs over the years and every time we had a bad SWR match it was an un-grounded radio or bad or broken coax or maybe a bad (or too long) antenna. I have 3 or 4 mag mounts, (that don't ground directly to the car) and I always get a pretty good SWR with them and I just plunk em on top and head off. I had a 30 year old center load antenna and the mount looked like it'd bolt right on the passenger mirror bracket on my 250 so I bolted it on, ran the coax behind the glove box and was off, it was only a temporary setup for a short trip to Idaho. But the on-board SWR was perfect. No needle movement at all on channel 1 and barely there on 40 and the thing got out like crazy. When I got back I hooked up an external meter to check it, and when I adjusted the antenna down, (set screw on the coil, took 15 seconds) I had a perfect match on channel 1 too! Haven't touched it in a year and haven't worried about bonding anything to anything.

I've used mag mounts on both my daughters' Honda Civics and never had a bad match. I'd really make sure it isn't another issue before bonding everything. I once put a base mount on a Corvette for a friend. It had a luggage rack on the rear deck lid so we used it for a ground plane. The SWR was about 1:2.5 so we ran a ground wire, just a #10 copper wire, down to a bolt on the frame and that got us down to about a a 1:1.8. We figured for a car made mostly of fiberglass, it was good enough, and it was. Worked great. All the antennas I mentioned had already, at one time or another been tuned or trimmed. As Greg said, many antennas come long so they can be trimmed down. Trimming up is like cutting hair longer, it's hard to do (and it looks stupid).

Anyway, hope you find an easy fix. Good luck. Let us know what you find.