This is what I did to mount an antenna bracket on the outside of my trailers... This was for Ham Radio/Scanner antenna but should work just fine for a CB mount.
I am not much of fan to drill thru the roof so I went for the side of the roof and found a spot where i could come into the back of inside cabinet to hide all of the cabling.
This is a mirror mount found at Radio Shack...
These two photos pretty much identify the game plan...
The flat piece was used to cover the RG cable going thru the side wall in the one photo. Then I filled both open ends with RTV to keep moisture out...
Once inside the trailer you can route the RG cable behind things to get to where your radio is installed. I don't have any RG cables visible with my install.
The antennas just clear the roof and have been in service here for more than five years now and work out just great. I actually mounted an identical install on the rear of the trailer roof on both sides...
You can just see the two side mounted antennas in this photo of my off-road POPUP trailer.
You didnt say what your RV was but if it is a CLASS C MH then the MIRROR MOUNT probably is the best solution for you. Then you can run RG cables thru the door weather seal to your CB radio mounted in the truck console area somewhere.
Good luck with your CB setup... In all my years of RV'ing I can say I have heard much CB operations among the RV'ers. I use mine in my truck console to monitor the truckers when on the Interstate. They all seem to know where all the hazards are located. I listen 99.9% of the time. Very seldom yak on it...
Cell phones is best for us to keep tabs on each other.. Also use the FRS family radio channels some around the camp sites.
Food for thought
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS