The technique is to make a measurement near to the frequency of interest of Rin at resonance of the length of line with open circuit at the far end, and to calculate the matched line loss (MLL) using Calculate transmission line Matched Line Loss from Rin of o/c or s/c resonant section.
Let’s demonstrate the measurement of Rin of an o/c resonant section around the 160m band, which we will then use to calculate MLL.
Above, the AA-600 connected to the cable using a F(F)-N(M) adapter, the cable is 305m in length and the far end is open circuit.
So lets scan around 1800kHz looking for a convenient resonance.
Ok, there is a resonance just a bit above 1800kHz. Let’s move the cursor using the freq+ arrow key, press the range- key a few times to narrow the scan and press ✔ to rescan.
Ok, closer now, but overshot a bit. Let’s move the cursor again and switch to All mode.
Above is All mode, X is just greater than zero, so we will shift freq down using the freq- arrow key watching X for the zero crossing.
Above, this is close enough. We can read Rin as 19.0Ω.
Above, calculating MLL from the input data we have 0.0074dB/m or 0.74dB/100m.
This whole procedure takes less than a minute using the stand alone instrument… in part due to the very effective human interface on the AA-600, you might think the designer knew how the instruments would get used, something you cannot say for a lot of analysers and VNAs (which are now the fashion).
The technique is particularly useful if the far end of the cable is not accessible, eg it is sometimes hidden in the interior of the drum.