Hi Connie..

...

I see no reason why a mast top mounted antenna and it's coax cable couldn't be plugged into the same radio antenna connection.<<

The connector that I bought for my HH C/Band fits my HH Uniden as well (after removing the duck whip) My only thought would be a proper impedance match twixt HH and masthead antenna. If the impedance doesn't match, there may be enough power loss to negate the benefit of the external antenna. So, yes...it's a good idea to talk to the service/techsupport dept<GG> Harvey/Ga M-17 Stargazer #294