What are the pro's and con's of lengenthing a mobile antenna? I have a
travel trailer that I would like to operate from with a mobile vertical
antenna off the back bumper. I standard 8' Huslter type mobile antenna
would be poor with most if its length running parallel the back side of my
aluminum framed trailer body. Would it be benefitial to add about 15 or
so feet of mast to the antenna below the coil? Would an additional 15 feet
of mast below the coil prevent me from tuning to resonance with the
adjustable whip on top? If so, any suggestions as to materials to do
so?

PS: I'm only planning on operating 75M and maybe 40M.

Ed K7AAT