I also recommend running a dedicated 220V circuit to the shack for your amp(s) I was plagued with the lights dimming, etc and after having to reset circuit breakers a few times decided I had to do something ! Yes, some work involved running the romex cable thru the attic, etc but well worth it.
Bob K6UJ Bob K6UJ On Feb 16, 2011, at 8:35 AM, Scott Ellington wrote: > Actually, the percentage voltage drop at 120 V is FOUR times that at 240 V. > (For the same power, wire gauge and length.) Since the KPA500, like most > tube-type amplifiers, uses an unregulated power supply, the extra drop can > significantly reduce output. For example, suppose the amplifier can put out > 500 W with a perfectly regulated input of 120 or 240 V. Say the line > voltage, at 240 V, drops 6 volts at full output. That's a 2.5 percent drop, > which reduces RF output by about 5 percent, to about 475 W. At 120 V, the > drop is 12 volts, 10 percent, which reduces the output by about 20 percent, > to about 400 W. You just lost 75 more Watts, each of which cost you $4. > > Keep in mind that 500 W output requires about 1 kW input, that the power > factor of the power supply is considerably less than 1, and that the high > peak currents make the effects of line voltage drop even worse. When > calculating effective line drop for the KPA500, I would use something like 2 > kVA, about 17 A at 120 V. The above example corresponds to a run of 220 feet > of AWG 12 (440 feet total), admittedly a very long run. > > Bottom line: If you are adding wiring, use 240 V. Run the amplifier on 120 > V only if you have no choice, or if the run from the distribution panel is > under about 50 feet. > > > Scott K9MA > > > On Feb 15, 2011, at 6:25 PM, K4SC wrote: > >> If I were going to the trouble to pull the wire, I'd run 220V. You give >> yourself the option of using a heavier amplifier in the future, and less >> voltage drop (twice as much on 120V). > > Scott Ellington > Madison, Wisconsin > USA > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
