Alan, Your analysis is correct - BUT --
Efficiency is one thing. but it has been previously discussed that higher DC voltages result in improved IMD. So the "best" voltage to be used is a compromise (efficiency alone is not the only consideration). My preference is to stay with the 13.8 volt output of my power supply and keep the voltage drop under full load to a minimum by using #12 or larger conductors and low drop (APP) connectors. My vote is to stay with a "systems" approach rather than concentrating on only one parameter. YMMV. 73, Don W3FPR Alan Bloom wrote: > The graphs show: the lower the power supply voltage, the higher the > efficiency. > > The reason: When you set the K3 to, say, 100W it has to put 1.4A into > the 50-ohm dummy load (P = I^2R = 1.4^2 x 50 = 100). > > The DC current through the PA transistors is pretty much directly > proportional of the RF current through the transistors. Whatever DC > current the PA transistors require to achieve 1.4A of RF into the load > doesn't depend on the power supply voltage. > > Since the transistor current is the same no matter the power supply > voltage, you get best efficiency (lowest power dissipation) at the > lowest voltage that is capable of sustaining the desired power level. > > Al N1AL > > > On Wed, 2009-06-03 at 19:04 -0400, Jack Smith wrote: > >> I've made some measurements of my K3's efficiency versus DC supply >> voltage, output and frequency at >> http://www.cliftonlaboratories.com/elecraft_k3_efficiency.htm >> >> Jack K8ZOA >> www.cliftonlaboratories.com >> > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
