Hello and thanks for ahy help you can provide.

I have a small assisted hearing type transmitter that normally uses the
shield of the mic cable for the antenna. I need to change to a fixed
antenna for a particular application where there is no mic cable to
extend out.

The manufacturer says the antenna wire for this 651.85Mhz unit should be
48" long.

Can anyone tell me what that would equal in a rubber ducky antenna?

Thanks.