On Sat, Nov 12, 2022 at 06:13 AM, Peer DL8YF wrote:
"both values should align at least within some khz"
Hello Peer
I think Wes has already commented on the matter very well, so I am not going to repeat here.
The SWR detection inside amateur radio transceivers is not using an impedance measurement technique. Instead, it uses a relatively simple SWR measurement circuit. Therefore, we cannot expect that "both values should align at least within some khz". Neither can we expect a high SWR measurement accuracy of such in-built devices. Their purpose is related to operational monitoring, especially the detection of antenna faults. We also have to be clear about the nature of the transceiver in-built measurements. Unlike with the FA-VA5, transceiver in-built SWR detection assumes a constant source impedance of 50 Ohms. Surely, common amateur radio transceiver PAs are not able to provide a constant 50 Ohm output impedance. This of course also affects measurements with external VSWR instruments.
A remote diagnosis of possible problems in your FA-VA5 is difficult, if not impossible.
I use the "Master Calibration" (SM50) as described on page 12 of the FA-VA5 manual. The FA-VA5 measurement results then compare well with measurements made with my Agilent 8753 network analyser (boat anchor :).
Unlike the "basic calibration", the "master calibration" is storing SOL calibration values permanently.?
I hope, this helps a little.
73
Dieter, VK3FFB
Dieter VK3FFB