From some of the posts I think I'm beginning to understand the terminology. We have a Perl with a Progen II, fuzz had me completely baffled until my wife printed off post 1218956. The other terms are compatable with the Progen II I think. I looked up the info on the F165 & F170 I don't think there is enough diffrence to justify the extra cost for the F170. The cost of the F165 is comparable to 2 used Progen II's The big advantage is being able to runseveral frequencies at the same time and reduce the time on the machine I guess. Are you able to power the F165 off the Perl or do you use the adapter? Thanks for all your helpful info.