New mount changes SWR

It's hard to tell from this camera view, but the coax appears to take off at a pretty sharp angle from the end of the strain relief at the plug towards the mirror mount. It may not be a problem, but if I had that much strain relief length, I'd probably have used a 90 degree elbow connector.

Also, FWIW, a teensy bit of silicone grease (not caulk) on the outside of the threads of the SO-239 on the connector will help prevent the ingress of water. So would a liberal application of either Fibreglas Raincoat Tape, or a goober of Coax-Seal around the whole connector.

But the mount itself looks nice. Before you put it on the mount tube, didja "brighten" up the mating surfaces of the mount and the rail with steel wool or sumpin'? If not, it's not too late to unmount the mount, clean up the surface, then remount the mount. It's possible that your old strap mount actually bonded better to the rail.
Also, cuz I can't tell for sure, is the insulated lead running towards the cab from the right lower mount bolt (in the pic) a DC ground?

73

 

Looks just like the DC ground i have on mine.
I was using copper braid but it turned green the first time running in the salt.

Handlebar has great advice,pull it all apart and clean everything up with steel wool or light sandpaper.

 

My ground straps ( shield stripped out of an old coax with lug ends attached) turned green also. Didn't bother me at all.

 

Probably did not hurt anything but i get picky......lol!

 

Further is good...

+1 on Handlebar's suggestion of waterproofing the connection. My recommendation is silicone Rescue Tape. Stretch it pretty good when wrapping it around the connector (down to cover an inch of the coax), and it will form fit and fuse to itself. You'll need to cut it away to remove it (which is actually pretty easy), but the connector will look the same as it did the day you put the tape on. No residue to remove, either.

If you can't find it locally, Amazon has it.
http://www.amazon.com/RESCUE-Self-Fusing-Silicone-Tape-BLACK/dp/B000ZTK6CI/