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OK, I've done another test, similar to your original test Jeff, and the
plot thickens somewhat.

Procedure was:
I did a calibration on the 8753, and on the Nano, using the same OSL
standards from the Nano.
The 8753 cal data was setup to assume perfect calibration standards.
Then I measured my Kirkby 'reference' attenuator on both devices, and
extracted the s1p data.

This data has been added to the github page and charted.


Interestingly it shows an approx 0.3 dB difference between the 8753 trace
and the Nano trace. I don't know where this is coming from yet, but it
appears that the Nano result has changed from the earlier PC based test.
Whereas the 8753 data looks about the same as what I got from the PC based
calibration test.

There is also a reference trace on the chart. This is the data Dr Kirkby
supplied with the attenuator. His data is the gold standard in this chart.
The 8753 line doesn't match the Kirkby reference, because I have set up the
8753 cal kit to assume perfect calibration standards for the purpose of the
comparison.
I believe that the difference between the 8753 line and the green reference
is due to the uncharacterised OSL standards.

So the chart is showing two things:
1. There is an offset occurring somewhere in the Nano calibration code. We
can attribute this to the nano as the 8753 data matches the first
experiment - which used a PC based calibration.
2. Both of these cals assume the calibration standards are perfect, and I
believe that is the reason for the difference between the 8753 line and the
green Kirkby reference trace.

Jeff, I wonder if is it possible that this small offset (1) is similar to
what you saw in your original results?

Roger