On Tue, 2009-01-27 at 21:15, [email protected] wrote: ... > Interesting thing is the current draw at each power level was > not what I expected. I expected the higher voltage to lower > the current at each power level. It did but a miniscule amount. > At 10 watts the difference was 0.03 amps. At 100 watts the > difference was 0.02 amps. I expected a lot more. > > The endpoint voltage for the long cable was 12.7 V. > For the short cable is was 13.9 volts. I kind of expected > the 100 watt amperage to decrease as the ratio of these two > voltages. Doing the math, the expected current draw would > have been 1.6 amps versu the 20 milliamps. > > Can someone explain this anomoly? > Brian/K3KO
Interesting. I believe the power supply voltage affects the maximum possible power but has very little effect on the current at any given power level. It makes sense if you think about it. Because there is a fixed impedance transformation ratio between the PA transistors and the antenna, the current in the transistors tends to be directly proportional to the current in the antenna. In a tube-type amplifier with a PI matching network, you can re-adjust the impedance matching for maximum efficiency. So for the same power level, higher PS voltage results in lower current. Al N1AL _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
