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Measure coax length with Transform, where does the length start?

 

Hello,
Measuring coax length has been discussed in several topics. However I have a query. I have calibrated at the end of the short coaxes delivered with the Nano (in my case NanoVNA H4) about 18 cm long and I am using Dislords FW 1.0.64. Nevertheless it seems to me that measuring coax length with the Transform method will include the length of the short coax, so the "measurement plane" seems actually to be at the connection point to the Nano itself. I know about the Marker/Measure in later FW, but I don't know if that FW makes the measurement start at the calibration plane (my guess) or at the Nano, so the same query for that. The question arose when I tested the iteration method to find the VF that I mentioned in another topic, my iteration method gave VF 59 % for a RG58 coax about 2 meters long, if I include the length of the short coax the VF would be 66 % which is more plausible for a RG58.
73/Torbj?rn
 

When you do your calibration, the device includes the cable length as part of the device. It doesn¡¯t matter if you do the calibrations at the vna or at the end of a 20 foot cable, that distance is calibrated out of the equations.

Sent by me

On Aug 14, 2021, at 17:12, Torbj?rn Toreson <torbjorn.toreson@...> wrote:

?Hello,
Measuring coax length has been discussed in several topics. However I have a query. I have calibrated at the end of the short coaxes delivered with the Nano (in my case NanoVNA H4) about 18 cm long and I am using Dislords FW 1.0.64. Nevertheless it seems to me that measuring coax length with the Transform method will include the length of the short coax, so the "measurement plane" seems actually to be at the connection point to the Nano itself. I know about the Marker/Measure in later FW, but I don't know if that FW makes the measurement start at the calibration plane (my guess) or at the Nano, so the same query for that. The question arose when I tested the iteration method to find the VF that I mentioned in another topic, my iteration method gave VF 59 % for a RG58 coax about 2 meters long, if I include the length of the short coax the VF would be 66 % which is more plausible for a RG58.
73/Torbj?rn

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