On 3/4/2020 2:56 PM, Adrian wrote:
I get the same on my KX3 on 12m , When using an antenna analyser the 12m radiation resistance is lower (much less than 50 ohm), with more reactance component than in the other bands, and when the ATU corrects the reactance component of the load, the current tends to be higher (multi-band antenna use with ATU). than the other bands with more radiation resistance values.
I suspect an understanding gap here. What you're describing implies a severe mismatch AT THE ANTENNA. A mismatched load (the antenna) is transformed by the transmission line to an entirely different impedance at every point along the line. The mismatch establishes standing waves on the line, and SWR is one measurement of that, BUT -- loss in the line causes SWR to gradually get smaller along the line, reaching its lowest value at the transmitter.
Computing programs like SimSmith and AC6LA's Excel spreadsheets can take measured data from analyzers that are capable of producing suitable files, and, if you know the cable's characteristics, can transform a measurement made in the shack to the impedance of the antenna itself.
Radiation resistance has meaning ONLY at the antenna feedpoint, and it's a characteristic of the antenna itself. It represents power that is radiated by the antenna. IF we could connect the analzyer at the feedpoint, we would measure its feedpoint impedance, Rs +jXs, but Rs is NOT necessarily the radiation resistance.
A study of texts like the ARRL Antenna Book (or equivalent in VK-land) are in order. There's a bit of a tutorial in slide show form on my website that might get you started on understanding on the transmission line part of it. http://k9yc.com/PacificonSmithChart.pdf The Smith Chart is a graphical means of understanding (and computing) what happens on a transmission line.
73, Jim K9YC ______________________________________________________________ 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
