Here's my take: Most if not all RF power meters will only be accurate at a 1:1 SWR (when there is resonance). The actual power can more accurately determined by reading the voltage and current and then only if the amp efficiency is known.
It's likely that neither the K3 or KPA500 meter is entirely accurate; the K3 would sense the 'bad' SWR and start a power foldback and the amp is a random location on the feedline away with the mismatch causing a sensing error. (Adding another random feed length would likely give a different reading.) >From memory, at 3:1 you have approximately a 25% 'reflection'. I didn't do the math to verify, but in this case happens to be the same as shown as added power in the KPA500. Perhaps someone else can add more. The K3 is producing the power and should be the more accurate reading. However, an improvement of 3:1 should be obtained before either the K3 or the more importantly the KPA500 applies any significant power (in fact the amp will 'complain' and switch to standby at ~2.1:1). That higher SWR in the real world comes back as heat, which is bad and shortens the life expectancy of the final(s). Make sense? Rick WA6NHC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Richard Sent: Wednesday, November 23, 2011 6:40 PM To: [email protected] Subject: [Elecraft] wattage on k3 vs kpa500 Hi Maybe some one can answer this. I set my k3 to 60 watts and measure 60 watts on my kpa500 meter with the amp in standby trnsmitting into a dummy load. When I switch to an antenna with a 3:1 swr the k3 still says 60 watts but the kpa500 now reads 80 watts with the amp still in standby. So which is correct or neither ? Thanks Richard ______________________________________________________________ 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
