During my MURS radio project one of the biggest aggravations was the poor SWR of the stock antenna mount. After messing with it for hours one evening I started trying different things. One of the things I tried was grounding the housing of the antenna mount. This made the SWR go down a lot. I came to the conclusion the stainless antenna tube and metal housing had caused a corrosion between the two and was messing up the antenna grounding. I decided to take it apart and clean it.
After removing the antenna mount from the trunk you get to this point. There are three screws to remove.
Then a set screw.
The plastic cover slips off.
I thought I would try to remove the tube from the housing for a good cleaning, but the tube is pressed all the way to the bottom. It's not coming out.
Removing the retaining pin...
...allows the connector to come out.
One problem I had was the piece on the left was not connected properly. It had came loose. It's supposed to connect the ground shield to the tube.
I soldered it back in place.
I also soldered a 10-gauge wire to the coax. I made it bulky so it too would contact the tube. I connected the other end to the frame ground.
I tried to solder the tube and housing also, but the stainless steel wouldn't take the solder.
I reassembled the antenna mount with the extra ground wire.
I hooked everything up and read the SWR again. It still sucked...but if I touched the tube to ground like I did before the SWR decreased. I threw up my hands in despair and went to bed.
Update: When I was finally able to get out and ride I noticed the CB/FM splitter killed my FM reception. I put the side antennas back to CB and FM and mounted the VHF antenna on my luggage rack.
You could have knocked me over when the ungrounded 1/4 wave antenna gave me a SWR of 1.1:1! The best I was able to do before was around 3:1.
The only difference between this setup and the others I've tried is this antenna mount has 17' of coax. The others had at most four feet. Apparently a longer coax helps?????