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On Sun, 15 Dec 2019 at 15:19, Jeff Anderson <jca1955@...> wrote:

A few years ago I made an open and a short female SMA standard for
calibrating my HP 8753C VNA (for the load I used a very nice 85052 female
3.5mm load). I never used the open and short above about 30 MHz, so I
didn't worry too much about their accuracy.

Fair enough.

With my purchase of a NanoVNA I thought I could put them to use in lieu of
the male standards the NanoVNA comes with. And so I thought I'd check
their accuracy, using my 8753C and the Rohde & Schwarz T-check method.

I'm a bit sceptical of the T-check method. R&S don't sell the device to do
this any any more, but they used to. They only sell verification kits based
on airlines and attenuators. Ken Wong at Keysight looked at it, and was not
impressed.

There's not the proper error correction in a nanoVNA to perform a T-check
anyway.

Of course, I had not characterized my standards, and so I thought, as a
first attempt at checking them, I would use the "stock" 3.5mm cal-kit
definitions that are stored in the 8753C.

The key parameters of the "stock" 3.5mm definitions (to match HP's 85033C
kit) are:

Open: C0 = 53, C1 = 150, C2 = 0, C3 = 0, and Offset Delay = 14.491 ps
Short: Offset Delay = 16.695 ps
Thru: Offset Delay = 0 ps

Depending on how you construct the standards, you are likely to get delays
longer than those. They are very short.

If you make your own standards, the parameters of the males and female will
almost certainly be different. I would suggest you modify the 85032B N cal
kit, as that has different parameters for the opens and shorts, which you
will have.

2. Why are the Thru Offset Delays in HP's Cal Kits all spec'd to be 0
ps? (Clearly the length of the thru's are not zero, so what is HP
referencing to determine that an Offset Delay is 0?)

Because they are based on a *"flush thru".* In other words, one standard is
male, and the other standard is female, so they connect together with zero
delay. HP can't guess the delay of your thru. For a "typical" female-female
thru the delay will be 41 ps, which should be entered into the calibration
standard #4 as 41 ps.

Thanks for any insight provided!

- Jeff, k6jca

Dave, G8WRB