Fred’s assessment is correct - the output power resolution below 25 watts is pretty low. But it is still putting out power, at least to a point. There _is_ a lower limit to input power - it involves the ability of the frequency counter to do its job. If the counter cannot get an accurate count, it won’t be able to corroborate the frequency for the correct band selection. This level is in the neighborhood of 1 watt, giving you some range to play with.
Enjoy playing with your KPA500! Jack, W6FB > On Jun 15, 2016, at 7:15 PM, Fred Jensen <[email protected]> wrote: > > Hmmm ... I guess first question is, what's the problem? 25 W to 20W is > slightly less than 1 dB, 0.16 S-unit. Just run barefoot? > > The LED Power display on the KPA500 is digital. It "measures the power," and > puts it into one of a number of bins. If something is in the bin, it lights > the LED. If the measured power isn't high enough for the lowest bin, all the > bins are empty, no LED's light up, although there is still RF being made. > > Measuring power with simple instruments is hard ... well, sort of impossible. > You can measure the voltage, but then you need to know the impedance, a > complex number, not easily measured with a DVM. You can measure the current > -- same problem. KPA500 is designed to emit 500W with 25-30W input. I think > you're pushing the envelope here and nothing is wrong. > > 73, > > Fred K6DGW > - Northern California Contest Club > - CU in the Cal QSO Party 1-2 Oct 2016 > - www.cqp.org > > On 6/15/2016 4:54 PM, James Bennett wrote: >> I share my KPA500 with a K3 and a KX3. When I want to operate JT65 or >> JT9 I normally run about 25 watts out, using the KX3 to drive the >> amp. With the KX3 set to 1.8 watts out, the amp gives me 25; with 2.2 >> watts from the KX3, I get 30 watts out from the amp. >> >> But, what if I want to run 20 watts? Or 15? When I back the KX3 power >> level below 1.8, the KPA500 shows zero on the LED power display. Does >> this mean it is no longer amplifying, or is it actually amplifying >> but not enough for the circuitry to determine how much? >> >> Jim Bennett / W6JHB Folsom, CA > ______________________________________________________________ > 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]
