Hi Dick, Some numbers: using the K3 Schematic, "K3S RF Board" Sheet 2, Section B1. The power meter uses a series Schottky diode detector. The low reasonable resolution is about 0.3 VDC, or 0.3 * .707 = 0.21 Vrms out of the directional coupler.
The Power for 0.21 Vrms is: 0.21^2 / 50 = .88 mW Assuming a 20 dB coupler 1:10 turns ratio, 0.88mW * 100 = 0.88W reflected power. Assuming forward power of 100 watts and 0.88 watt reflected power the return loss is: 10 * log(100 / 0.88) = 20.6 dB Using the calculator: https://www.allaboutcircuits.com/tools/vswr-return-loss-calculator/ 20.6 dB Return Loss computes to VSWR = 1.222 Therefore, the best lowest estimated K3 VSWR, assuming a 20 dB coupler, is about 1.2. Check my numbers. John KN5L On 7/27/18 9:58 AM, Dick Dickinson wrote: > I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my > antennas per K3 SWR Numerical Readout. K3EZ will record 1.0:1 SWR in band > sweeps. > > Can the K3(S) Numerical Display show 1.0:1 SWR? If so, is there a likely > reason why K3EZ will show 1.0:1 while my K3 will only go as far down as > 1.1:1? ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
