Thanks to all that replied. What I am wanting to build is an antenna
that will replace the "rubber duckie" one that came with the radio. It
is a 2m/70 cm hand held and I found when I replaced the original
antenna with a telescoping one on 2m my transmitting distance on 2m
improved dramatically. So I am trying to do the same thing on 70cm. I
would like to make an antenna that will connect directly to the BNC
socket on the radio. Not one that is connected to coax and the antenna
erected higher or whatever. I will probably just try a 1/4 wave length
connected to the centre of a BNC plug and see how it goes.
Cheers
Max