Joining UHF antenna Cable

G'day perf,
I'm just going through this issue at the moment. I'm in a 4x4 club and don't seem to get as good a reception as some of the other club members. They can hear people further away than I can.
My coax has 3 joiners in it......one about 1 foot from the antenna (behind the grille), another one just inside the passenger's footwell (where the cable goes through the firewall) and a 3rd right at the back of the radio (the radio came with about 4" of cable and a male joiner attached).
Don't get me wrong, my radio still works very well, just not quite as well as some other blokes. Also, my antenna is only a 4.5db. It's one of those on a sprung base with about a foot long base and then a screw-on stainless wire with a coil half way up.
I'm not sure whether to get a 6/9db antenna &/or replace the coax and cut out the 1st 2 joins I mentioned above. I guess the 2nd idea would be cheaper to try and may give me better performance; so I'll try that first.
So, to answer your question, you shouldn't have any dramas just putting a joiner in near the grille.

While not ideal one joiner will not introduce much loss if done correctly. If water is allowed to enter the connector capillary action will suck it the full length and it will drip out at the radio end so keep the join under the bonnet out of the rain.

Best not to have any joiners as they rarely make a good connection.
the normal coax plugs are not waterproof and as has been stated once water has got in it is stuffed.
If you must have a join put it under the bonnet and wrap it in fresh self amalgamating tape EVERY time it is removed/reconnected.
the best method is to run a new cable from the radio to the antenna base and when the antenna is removed put the cable in waterproof bag under the bonnet.

Best option would be to buy an antenna that is removable. One that can be unscrewed leaving only the base. If height is a problem then GME has a range of antennas that can be screwed into the one base. Depending on your needs at the time. AE4700 series.

Utemad

do you need to remove the antenna (or the complete antenna,base and lead if so why)?
because the more joins you have then the more loss you have when it comes to UHF.