Ready for tomorrow. Hopefully it sorts the problem out. 
UPDATE:
Tried 10m today.
I managed Canada & Lithuania on a car battery, then switched to my tiny 12v 3ah battery to confirm there are no power problems, and bagged a USA contact. I managed Serbia but canāt remember which battery I used.
I think problem is solved. Just need more drive out of the mic (itās a bit quiet). Nearly nearly thereā¦ 