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Syd,

I suggest you read this document which will get you more familiar with the NanoVNA. It is in the files section of this group

/g/nanovna-users/files/Absolute%20Beginner%20Guide%20to%20The%20NanoVNA/Absolute_Beginner_Guide_NanoVNA_v1_6.pdf

Also read the Wiki for this group which is full of great information. You can also search the group for info on topics of interest. There are some very knowledgeable people in this group who have contributed to posts in the past.

Roger

Yep. One day long ago I was in my shack in the evening and I heard "snap, snap, snap, snap..." and wondered what the heck? I quickly found the source. I had a feedline's PL259 disconnected and dangling free. Every half a second there was a bright 2" arc from the feedline to a nearby grounded surface. It had started to snow.

I developed the habit long ago of shorting out any signal connectors before mating them when working at the bench or when connecting antennas. As others have mentioned, I usually just just use my finger between the center and shield while touching the ground of the device I'll be connecting it to. All my antennas in the shack go through switches which keep the antenna connected to ground until I switch it to a radio or analyzer. I also usually have Polyphasor or similar in line.

Syd,

You have to calibrate using the RF demo board Short, Open and Load in order to establish the measurement "Reference Plane" right at the U.FL connector. If you calibrate on the NanoVNA and then connect the cable you will get an impedance transformation due to the cable being used and incorrect measurement results. Save the calibration results to a slot on the NanoVNA so you don't have to repeat the cal procedure every time your turn on the device.

The type of NanoVNA you own will determine how many data points you get for the frequency range you selected. For example the older 2.8" have 101 and the NanoVNA-H4 with DiSlord firmware has 401. With 401 data points and 900 MHz. you have 2.5 MHz. between points. Some NanoVNA devices/firmware support "interpolation" so as you can zoom in the frequency range without re-calibrating but you have to use this feature carefully. For best accuracy it is better to do a calibration over a narrower frequency range and save that to a different slot for later recall if needed.

Roger

Syd,
Are you remembering to press the RESET menu button in the Cal menu immediately prior to pressing the Calibrate button?
You need to do that to clear old data from device RAM.

Syd - please review the NanoVNA forum's WIKI - link at the bottom of every email.
You will find alot of good info there.

Also please use the search function of the messages section (search help doc is the 1st link in the WIKI) as all your questions have been asked a few times over the past 2 years.
Cheers,Larry

Calibration only occurs at the points in the scan, 101, 201, or 401 points depending on the type of nanoVNA and the frequency.? If you do a cal from 1 to 900 MHz with 101 points, you only get a calibration point about every 9 MHz.? The nanoVNA will interpolate between these, but if the actual baseline isn't smooth between these points, the cal be pretty far off for measurements made there. It's best to do a cal over the frequency range with number of points that you intend to use for the measurement.

Yes.? You should do a cal at the end of the pigtails supplied with the board.? It's easiest to do this using the SOLT supplied on the board.

No, I used the items that came with the Nano. But the board tested OK when connected to the demo bd for the open, short, 50, 33 & 75 ohm test points on the bd!
Everything seems to work except the resolution sucks on the smith chart. Since I think there are only 11 calibration points stored during calibration, I think I have to set up a smaller scan when using the smith chart to get a smoother curve. But the tutorials all seem to mention using the wider scan: 500KhZ - 900MHz. Perplexed.
syd/wt1v

I just found the TAPR VNA files in the Files section and now I am curious about this application that has documentation and zip files, and looks like it is made to work with Windows. Is this application project meant to be used as a user interface from the computer to run the NanoVNA? I know someone made a LabVIEW version of this application to do this very same thing, so is this just another version of the same user interface?
syd/wt1v

Syd,

Did you calibrate using the short, open and load on the RF Demo board?

Roger

On 8/13/21 9:17 AM, Syd via groups.io wrote:

I just found, in the Files section of this forum, this document

"NanoVNA RF CalibrationConsiderations and Procedure-v1.1" (you can tell I'm rather new to this forum and am still learning about all of it's possibilities)

and after an initial perusal of this document, it looks like all my questions are answered here! I did notice that the calibration procedure looks like it is being done at the ends of the test cables as we discussed. Also I see that it mentions using 2 50 ohm dummy loads in this document for the isolation CAL! Luckily, I just bought a spare dummy load to go with the Nano.
73
wt1v

Indeed.. I find that I wind up with a selection of barrels and other similar gender changing.? If you're doing precision work, where mm count, then you probably want loads in both configurations to match the UUT. But for run of the mill, the difference in cal between a load with a jack and a load with a plug, and a jack/jack adapter is small.

On 8/13/21 8:42 AM, Syd via groups.io wrote:

When calibrating the NanoVNA, one plugs in the open, short, & dummy load (O, S, L) directly into the NanoVNA; hence, the calibration plane is at the unit itself. Since I'm using connector cables to test DUTs, wouldn't it make more sense to plug in these (O, S, L) to the end of the test cable and make that the calibration plane more accurate?

Yes.

The isolation and through calibration steps need to be done only when measuring DUTs throughput response such as filters and such. So the through cal step should be done using both measuring cables connected together in series I assume.

Yes

The isolation cal step is a little confusing. I assume no cables need to be attached to the NanoVNA. Then there should be either a dummy load or an attenuator connected to the S11 port. And then the isolation cal should be done.

at the end of the cable, if you're using them.

I just found, in the Files section of this forum, this document

"NanoVNA RF CalibrationConsiderations and Procedure-v1.1" (you can tell I'm rather new to this forum and am still learning about all of it's possibilities)

and after an initial perusal of this document, it looks like all my questions are answered here! I did notice that the calibration procedure looks like it is being done at the ends of the test cables as we discussed. Also I see that it mentions using 2 50 ohm dummy loads in this document for the isolation CAL! Luckily, I just bought a spare dummy load to go with the Nano.
73
wt1v

You can connect the nanoVNA to the mac using the latest version of SimSmith.

See



for an overview

Intro toSimSmith is here:

youtube.com/ae6ty

You can download SimSmith here:

ae6ty.com/Smith_Charts.html

ward

Syd,
Yes you should calibrate at the end of the cable, not the VNA connectors. solation iswhen a load is attached to both inputs at the same time o r if you have only one load, just to ch1. Only the through measurement connects the two inputs together.
Gary
W9TD

When calibrating the NanoVNA, one plugs in the open, short, & dummy load (O, S, L) directly into the NanoVNA; hence, the calibration plane is at the unit itself. Since I'm using connector cables to test DUTs, wouldn't it make more sense to plug in these (O, S, L) to the end of the test cable and make that the calibration plane more accurate? The isolation and through calibration steps need to be done only when measuring DUTs throughput response such as filters and such. So the through cal step should be done using both measuring cables connected together in series I assume. The isolation cal step is a little confusing. I assume no cables need to be attached to the NanoVNA. Then there should be either a dummy load or an attenuator connected to the S11 port. And then the isolation cal should be done.
syd/wt1v

On 8/13/21 8:12 AM, David Eckhardt wrote:

When connecting any length of coax to any sensitive measurement instrument,
I ALWAYS first grab the end of the coax and effectively short the end with
a finger or hand. If there has been a recent lightning storm, you might be
surprised and the discharge might surprise you in an undesirable manner.
The cylindrical capacitor that makes up the coaxial cable can hold a charge
for a very long time.

Blowing dust, snow, or rain, are even more of a charging hazard than the field from a passing thunderstorm.? Continuous charging. It charges until something breaks down, so you get a buzz or continuous clicking. A sort of relaxation oscillator.

Fooling around with this kit the other day I noticed 2 things. The smith chart, when calibrated from 1M - 900M, gave a not so smooth graph for the various smith charts. How do I fix this resolution problem? Maybe a smaller calibration range? Also, when measuring, using the logmax traces for the various filters, all looked OK except for the BSF and BPF filters. Their frequencies were off from what was shown on the demo board. So I'm guessing that this cheap board has it's limitations and I should just except the results and ignore the posted resonant points.
syd/wt1v

On 8/13/21 8:06 AM, Syd via groups.io wrote:

I saw a video about the dangers of using the nanoVNA by connecting to the antenna coax: static buildup on the coax. So I guess one way around this is to measure right at the antenna. The nano is portable. But that still leaves the coax so I suppose that I should short out the coax before measuring it. Any other measures/precautions about measuring out doors antennas?
syd/wt1v

Static will build up on the antenna, not just the coax. Or even the stuff sitting on the bench.? The ESD sensitivity varies substantially among the various small VNAs. Some have resistor bridges/pads right on the inputs.? Others have MMIC switches. The latter are more sensitive.

The other thing to worry about is nearby transmitters inducing sufficient power into your antenna to cause problems.


I suppose, one could check for any of these by measuring the AC voltage across a 50 ohm load hooked up to the UUT, with a simple (cheap, sacrificeable) diode probe. A 1N4001 and 0.01 uF would probably work, since you're looking for "volts" not "microvolts". A $10 DMM, diode, etc.

When connecting any length of coax to any sensitive measurement instrument,
I ALWAYS first grab the end of the coax and effectively short the end with
a finger or hand. If there has been a recent lightning storm, you might be
surprised and the discharge might surprise you in an undesirable manner.
The cylindrical capacitor that makes up the coaxial cable can hold a charge
for a very long time.

Dave - W?LEV

On Fri, Aug 13, 2021 at 3:06 PM Syd via groups.io <nhuq1@...>
wrote:

I saw a video about the dangers of using the nanoVNA by connecting to the
antenna coax: static buildup on the coax. So I guess one way around this
is to measure right at the antenna. The nano is portable. But that still
leaves the coax so I suppose that I should short out the coax before
measuring it. Any other measures/precautions about measuring out doors
antennas?
syd/wt1v

--
*Dave - W?LEV*
*Just Let Darwin Work*

I saw a video about the dangers of using the nanoVNA by connecting to the antenna coax: static buildup on the coax. So I guess one way around this is to measure right at the antenna. The nano is portable. But that still leaves the coax so I suppose that I should short out the coax before measuring it. Any other measures/precautions about measuring out doors antennas?
syd/wt1v