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David

I have two NanoVNAs and two 1-3000 MHz RF bridges. I get identical results with all four. The VNAs are calibrated with one set of supplied OSL terminations. When I use the bridge with the NanoVNA I connect Port 1 to the Input of the bridge, Port 2 to the output, and terminate the REF port with the NanoVNA 50 ohm load. I then calibrate the VNA for "Through" only with the DUT terminal open. This sets the CH1 Logmag return loss to zero. From this point forward calibrated NanoVNAs give identical readings to the RF Bridge down to reasonable levels. Once Return Loss hits 30 dB and beyond I pay no attention to discrepancies because they are meaningless for the most part.

I use a similar setup when using the RF Bridge with my Rigol Spectrum Analyzer. Tracking generator output to RF Bridge Input, RF bridge output to spectrum analyzer input, NanoVNA reference load on the REF port and the DUT port open. I then normalize the spectrum analyzer to zero, connect the DUT, and read the return loss directly from the screen.

Up to 30 dB or so of return loss all four devices produce reasonably identical readings through 750 MHz plus or minus one dB.

WA8TOD