There are two windings on the PA output transformer: 1:1 and 1:4. We select one of these based on power level, battery voltage, and in some cases, operating mode.
In the 1:1 setting, the PA drain impedance is 50 ohms, making it more efficient for at power levels, reducing current drain. In the 1:4 setting, the PA drain impedance is 12.5 ohms; the transformer steps it back up to 50 ohms for the low-pass filters. In this case it's more efficient at higher power levels, at the expense of higher current drain. Wayne N6KR > On Jan 26, 2021, at 11:07 AM, Julia Tuttle <[email protected]> wrote: > > The manual states in a couple spots that the KX3 can transmit more > power-efficiently when output power is at or below 3 Watts. > > Why is this? Is there an (additional?) amplifier stage that is bypassed at > these lower power levels? > > Thanks, > > Julie > ______________________________________________________________ > 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 > Message delivered to [email protected] ______________________________________________________________ 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 Message delivered to [email protected]
