Sanjaya wrote:

I have a 50 ft. random wire with coax lead and PL-259 connector for use with my R75

Is there an adaptor that can be used to connect that antenna to a portable radio's antenna jack?

Most likely... it would depend upon what type of jack the portable has.

dxAce
Michigan
USA

http://www.iserv.net/~n8kdv/dxpage.htm