Hi Colin, Large transformers are very efficient unless... made specifically for the ham market! Any commercial 120-240 multi-KW unit should exhibit less then 5% loss. Sorry for the tardy reply but, this was buried in my inbox under RS-232 chatter. 73 & Good morning, Marv WC6W -- Colin Lamb wrote: I have a 6.5 KW 120 volt Onan generator. I have been told that because it uses a transformer as part of a regulator system that it is not recommended to reconnect to produce 240 output. Question: What sort of efficiency am I looking at to use a 120 to 240 transformer? Is there a particular type that might be more efficient? Would I be looking at 15% losses? Note: This is an amps question, because I may run my 240 amplifier off the generator. 73, Colin K7FM _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ___________________________________________________________________ Try Juno Platinum for Free! Then, only $9.95/month! Unlimited Internet Access with 250MB of Email Storage. Visit http://www.juno.com/value to sign up today!