The AM2060 needs 24V for it's internal electronics and to drive the antenna tuner. It then supplies the 12V needed by the PRC77 set.
The AM2060 has a plug on the back that mates with the mounting tray. The mounting tray has three connectors on it and one of these will be the lead you describe. It probably has four wires with two being joined for the positive connection and two being joined for the negative connection.
You need to connect it to 24V. If you are going to install it in your landrover and don't have a source of 24V you will need to buy a 12 to 24 converter with sufficient output.
Howard
Thanks Howard, yes it's as you describe, 2 pairs of wires connected together.
As regards the 24v source, when you mention 'sufficient power' how much are you talking about?
Despite my penchant for originality, for practical reasons I was thinking of not refitting the 28v generator (a) because of its weight and I now have parabolic springs fitted and (b) I don't have one or the cabling.
Thanks for your reply, Daryl