Is it a viable method to do calibration of the VNA with a transmission line attached, so that when the DUT is attached to end of that line the measurements are true measurements of just the DUT?

Yes. Instead of doing the OSL calibration at the unit, do the same at the
end of the coaxial feedline. Outside of a bit of loss due to the coax,
then your measurement plane will be at the end of the feedline.

Dave - WØLEV

On Wed, Nov 13, 2024 at 6:13 PM Akai Moto via groups.io <akai.moto=
protonmail.com@groups.io> wrote:

Is it a viable method to do calibration of the VNA with a transmission
line attached, so that when the DUT is attached to end of that line the
measurements are true measurements of just the DUT?

--

*Dave - WØLEV*


--
Dave - WØLEV

Yes; in fact I had to do this to calibrate measurements made on a 1296 MHz
bias tee using microstrip transmission lines.

Zack W9SZ

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On Wed, Nov 13, 2024 at 12:13 PM Akai Moto via groups.io <akai.moto=
protonmail.com@groups.io> wrote:

Is it a viable method to do calibration of the VNA with a transmission
line attached, so that when the DUT is attached to end of that line the
measurements are true measurements of just the DUT?

That's actually the main purpose of calibrating a VNA, to remove everything
from the measurement except the DUT.

73,
-de James/AC0CW

On Wed, Nov 13, 2024, 13:13 Akai Moto via groups.io <akai.moto=
protonmail.com@groups.io> wrote:

Is it a viable method to do calibration of the VNA with a transmission
line attached, so that when the DUT is attached to end of that line the
measurements are true measurements of just the DUT?

My question is type of "just checking" question. All the directions for the various vna's say to do the OSL at the vna port. I guess they assume anything connected after that is the DUT.

I also asked for a 2nd reason. If all the stuff pre DUT makes things very wonky, will the vna fail an OSL calibration? In other words, how much calibration room is there in the tests?

As a new question - has anyone seen big diff in results in doing OSL at the port vs OSL at the end of a line where DUT connects?

You always want to calibrate at the end of your test cables, or somewhere in your test setup as close to the DUT as possible. The nanovna's have a large calibration range.

QUOTE: My question is type of "just checking" question. All the directions
for the various vna's say to do the OSL at the vna port. I guess they
assume anything connected after that is the DUT.

When the DUT is connected directly to the VNA, yes, calibrate right at the
VNA SMA connector.

BTW: The OSL cal is good only for a single port measurement and cal. If
you need a through measurement, you must also do a through cal, or OSLT.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I also asked for a 2nd reason. If all the stuff pre DUT makes things very
wonky, will the vna fail an OSL calibration? In other words, how much
calibration room is there in the tests?

Always do a "RESET" and "CAL" before attaching the DUT of anything to the
S11 port (or through for the S22 port as well). Whatever attachment of the
DUT has with the cal is ..... nothing. Attachment of any DUT to the ports
will not disturb the cal as long as power to the VNA is not recycled. The
cal is there to establish your measurement, be it right at the VNA or
extended with appropriate cabling.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

As a new question - has anyone seen big diff in results in doing OSL at the
port vs OSL at the end of a line where DUT connects?

Absolutely yes! You should cal at the point of DUT attachment. If you
connect the DUT through say 30-feet of 50-ohm coax, the cal should be done
at the end of the 30-foot length of coax. Doing so eliminates the coax
from measurement of only the DUT.

Dave - WØLEV

On Wed, Nov 20, 2024 at 2:37 PM Akai Moto via groups.io <akai.moto=
protonmail.com@groups.io> wrote:

My question is type of "just checking" question. All the directions for
the various vna's say to do the OSL at the vna port. I guess they assume
anything connected after that is the DUT.

I also asked for a 2nd reason. If all the stuff pre DUT makes things very
wonky, will the vna fail an OSL calibration? In other words, how much
calibration room is there in the tests?

As a new question - has anyone seen big diff in results in doing OSL at
the port vs OSL at the end of a line where DUT connects?

--

*Dave - WØLEV*


--
Dave - WØLEV

Hi , some figures describing the most common calibration possibilities of a VNA.

You calibrate for the point you want to understand

If you want to know what a transmitter will see as the coax is plugged into it - calibrate at the VNA and plug the cable in

If you want to know how a poorly matched antenna really looks (before the coax distorted that some more ) calibrate at the antenna end of the coax then plug it into the antenna

etc

1) Never try to run all of the calibration points. Sure the firmware will encourage it, but if you close save and return then you will notice that calibration points were lost. This is at least true on the F, Fv2, and H4. Though it's hard to say what happens in the Fv2 wince it wont actually show what calibration points were saved. Fv2 also lacks a function for Isolation where F and H4 both have it. With this in mind it is prudent to ONLY calibrate for what you need so you don't waste time on calibrations that will be dumped. ie Load, Short and Open save fine. But also do Thru and you will loose data.

2) If you are unlucky enough to have an F, it's good hardware but there is a bug in Calibration. Use back not DONE after calibration, a bug will cause all calibration data just recorded to be lost.

3) Always make sure anything you don't want measured is attached when you calibrate. If you have a very long cable and you cannot move it and you are sure its good. Then make sure your dummy, open and short are attached to the end of that wire when calibrating.

4) If you want to include a wire or some other device in your calibration process, start with a cleaner calibration that only includes the hardware needed to connect the VNA to the wire. Now test that wire or device. If it is good, then you can now include it in any calibration. Thus it will be treated as part of the VNA not the antenna.

5) Always make sure your stimulus is set before calibration. Although the VNA will allow testing outside the calibrated range. It will no longer be accurate.

All:
RE: Ray's post, comment 5:

Newbies may not yet realize what iseant by STIMULUS ".

That's the frequency range you want to scan. When you click Stimulus you
are greeted by two important frequency choices:
"START" is the lowest frequency for starting the scan.
"STOP" is the highest frequency where the scan will stop.

As others have pointed out, you want to do the calibration when you have
chosen a broad frequency range that covers the our need.

For example, of you want to adjust the resonant frequency of a 14 MHz yagi,
you will want to pick the START and STOP frequencies to span that range.
You might choose a range like 12 MHz START and 16MHz STOP.

Calibrate the device over that range, or close to it-_- not the default
50KHz to 900 MHz!

73
Bill K2TNO

On Thu, Nov 21, 2024, 7:09 PM Ray Lulling via groups.io <ray=
innovativetimingsystems.com@groups.io> wrote:

1) Never try to run all of the calibration points. Sure the firmware will
encourage it, but if you close save and return then you will notice that
calibration points were lost. This is at least true on the F, Fv2, and H4.
Though it's hard to say what happens in the Fv2 wince it wont actually show
what calibration points were saved. Fv2 also lacks a function for Isolation
where F and H4 both have it. With this in mind it is prudent to ONLY
calibrate for what you need so you don't waste time on calibrations that
will be dumped. ie Load, Short and Open save fine. But also do Thru and you
will loose data.

2) If you are unlucky enough to have an F, it's good hardware but there is
a bug in Calibration. Use back not DONE after calibration, a bug will cause
all calibration data just recorded to be lost.

3) Always make sure anything you don't want measured is attached when you
calibrate. If you have a very long cable and you cannot move it and you are
sure its good. Then make sure your dummy, open and short are attached to
the end of that wire when calibrating.

4) If you want to include a wire or some other device in your calibration
process, start with a cleaner calibration that only includes the hardware
needed to connect the VNA to the wire. Now test that wire or device. If it
is good, then you can now include it in any calibration. Thus it will be
treated as part of the VNA not the antenna.

5) Always make sure your stimulus is set before calibration. Although the
VNA will allow testing outside the calibrated range. It will no longer be
accurate.

On Thu, Nov 21, 2024 at 04:08 PM, Ray Lulling wrote:

Never try to run all of the calibration points. Sure the firmware will
encourage it, but if you close save and return then you will notice that
calibration points were lost. This is at least true on the F, Fv2, and H4.

Not so. If you save into one of the memory slots, the full calibration is saved, along with all your trace and stimulus setup. All you need to do is use the 'recall' memory to get it back whenever you want it for that same test setup. I always do a full calibration. On the left side of the screen, there is a C followed by a number - that number is the memory slot that your calibration was read from. If there is a C with a number, the device is calibrated from whatever was in that memory slot. Slot 0 is read at power-on. The only time calibration points are lost is if you select 'done' in the calibration menu without saving first - then when you power off, that calibration data is lost. Recent versions of firmware label that button 'done in ram'.

Two common mistakes:

1/ Making measurements with a calibration, certainly done in the right place, but not on the same frequency range. Nothing indicates the range used when you reload a calibration range.

2/ Forgetting to do a RESET on the nanoVNA box. If you forget, in the best case, it will produce a Smith that goes out of the circle but not always. RESET of the measurement bridge is essential before a calibration.
--
F1AMM
François

On Thu, Nov 21, 2024 at 09:10 PM, François wrote:

Nothing indicates the range used when you reload a calibration range.

Not so - all recent DiSlord firmware for nanovna names the save slot with the frequency range used to calibrate. Also, when you restore a calibration, it also restores the frequency range, so you can easily see which range was calibrated.
IF you only calibrate using nanovna-saver software or nanovna-app, you would need to manually name your calibration files with the frequency range used.
Stan KC7XE

IF you only calibrate using nanovna-saver software or nanovna-app, you would need to manually
name your calibration files with the frequency range used.

** Yes, I use nanovna-saver. I name my files as
Cable BNC 1 m 0.1-30 MHz (lin) 20seg.cal
--
F1AMM
François

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