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DIY SOL Calibration Kit

By Andy •  2017-11-26 13:28:14 •  108 clicks
Hello,

I added an N-to-SMA adapter on my KC901V, and followed the following instructions to make SOL calibration components from male Amphenol SMA connectors:

http://www.qsl.net/in3otd/electronics/VNA_calkit/SMA_male.html

They seem to work well, but I wonder if the values I input under "Calibration kit data" in the FUNC menu are correct.

The physical length of the SMA connectors, from the white disk from which the male pin emerges to the back of the connector where I solder load resistors, etc. is 10 mm. I am guessing that the velocity factor of the connector is around 0.7. Hence the electrical length should be 10 / 0.7 = 14.3 mm.

Should I input 14.3 mm for short, open, and load length under "Calibration kit data"? Or am I misinterpreting the meaning of those fields? Those fields could also mean round-trip delay (requiring a value of 28.6 mm), or expect a negative offset (-14.3 mm).

I would really appreciate it if BG8NPK could comment on this.
6 Reply | until2017-12-19 00:22Add a reply
    VK3NH  10 days ago#1 -Reply

    Genuine post


    mjohnellis  14 days ago#2 -Reply

    Please disregard my comment about the increasing length for N to SMA adapter. It does not apply and I am unable to edit the comment.


    mjohnellis  14 days ago#3 -Reply

    After looking at the article more closely, I noticed the author used 45.9ps for the offset delay. I think this is the correction factor for your SOL. If you divide 14mm by speed of light you get 46.7ps which is pretty close.


    mjohnellis  14 days ago#4 -Reply

    Shouldn't the correction be a little longer because of the N to SMA adapter? This was a good article. It was interesting in another version, that two resisters for the load were better than one but four were worse than two. This was probably due to capacitance increasing faster than inductance was decreasing.


    VK3NH  18 days ago#5 -Reply

    Andy,

    Nice work on making and using the SMA cal set I also saw information on.

    I like how you worked out the correction figure. That should go in the manual.

    regards Noel


    Andy  23 days ago#6 -Reply

    To answer my own question, a value of around 14 mm appears to be correct for this kit. This is confirmed by measuring S11 phase over frequency with nothing attached to the N-to-SMA adapter. If calibration was performed properly, phase should be 0 across the entire range.


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