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Port extensions on waveguide (not-coax) device.

Question asked by drkirkby on Apr 11, 2013
Latest reply on Apr 12, 2013 by Dr_joel
I want to measure |S11| of some horn antennas for amateur radio use at 10.368 GHz on an HP 8720D, as well as |S21| to compute the gain of two identical antennas. The VNA has option 1D5 and 010, so has only 3 receivers and so can't do true TRL calibration. 

Given this is just for amateur purposes, buying a waveguide calibration kit is not an option, so I intend making my own. From what I have read (Agilent application notes and Joel's book), this does not look to be rocket science in waveguide . 

My home-made cal kit is going to consist of a couple of precision WR90 loads, a 9.7 mm thick quarter wave shim and a short. I might add the "standard section" as included in Agilent cal kits. The short and shim are on order, so I don't have them and cant do a wavguide calibration. 

My issue comes with checking the cal kit - how do I know if it works or not? 

If I do a one-port calibration than with a waveguide short, I assume I will see a short at all frequencies. But what if I add a spacer of say 5 mm, and apply a port extension of 5 mm? Would the VNA take into account the dispersion in the waveguide or not? Would it show a short at all frequencies? 

My gut feeling is the port extensions might be useless for waveguide devices, but am I wrong? 

Dave, G8WRB