Hi David, A data point. The Kahn envelope restoration scheme is best employed for low duty cycle signals, like SSB, and employing tubes that were happy in plate modulated AM service. Their power out to plate dissipation ratio was typically 4-1. RTTY, CW and modern oxide cathode tubes with fragile grids are not valid options. To those who've drifted, my apologies for an "original topic" poating. 73 & Good evening, Marv WC6W http://wc6w.50webs.com/ -- "David G4FTC" wrote: I've been following the thread and have an observation which I haven't seen anyone else mention. Most professional linears (or up-market amateur units) have a rated rf output the same as the anode dissipation of the tube, i.e. a 1500 watt output amplifier will use tube(s) with an anode dissipation of ~1500 watts. Of course more power out can be obtained from a given tube in low duty cycle modes, but for high duty cycle modes such as RTTY, JT65 etc., it doesn't seem an unreasonable yardstick when designing an amp. David G4FTC _______________________________________________ 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 1GB of Email Storage. Visit http://www.juno.com/value to sign up today!