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On 10/17/21 6:28 AM, Joe WB9SBD wrote:

When you do a calibration

open/short/50,

Stimulus from 3 to 30 Mhz.

it should then be accurate between 3 and 30 Mhz correct?

OK you calibrated with the 3 to 30 Mhz scan width.

Now if you change the stimulus width to like 14 to 14.5 Mhz.
and not do a new calibration,

is the calibration still good since this narrower window is still inside the original scan width/

Joe

Yes, for the most part.? Let's say you have the original NanoVNA which uses 101 points. Your original cal is 101 points over the 27 MHz between 3 and 30, so about 270 kHz/point.? If you "zoom in" to 14 -14.5, the VNA interpolates between the 3 or 4 points covering that range.? Since it's unlikely that the VNA radically varies over that bandwidth, you'll get good measurements.


A notable exception might be if you're calibrating at the end of a longish feedline.? Then, there could be significant variations over a narrower frequency range (for instance, if you happened to be exactly 1/4 or 1/2 wavelength right in the middle of the band).

When you do a calibration

open/short/50,

Stimulus from 3 to 30 Mhz.

it should then be accurate between 3 and 30 Mhz correct?

OK you calibrated with the 3 to 30 Mhz scan width.

Now if you change the stimulus width to like 14 to 14.5 Mhz.
and not do a new calibration,

is the calibration still good since this narrower window is still inside the original scan width/

Joe

Excellent explanation Gregg - thanks!
I also stepped into the same trap

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

73
Martin 9A2JK

From Jose Miguel Vaca, VK3CPU. In beta testing.
Designed to help make toroids more accessible to designer/builders. Currently supports designing inductors, but will add support for suppressors soon. Optimised to work on mobiles, but should also work on desktop browsers. (Although layouts need work.) Looking forward to constructive feedback or bug reports. It supports the most common ferrite mixes and uses manufacturers data and equations for calculations.

Hello to the group,

I have tried this before but ran into such a brick wall that I had to walk away from it. That said some time has passed and I am trying this again. I have a semi newer H4 Version 0.5.0 and am having a problem getting windows to recognize the VNA.

With that said, I am ready to give it a try again. Based on my current position, what is the next step when you plug it in and get the message below?

Thanks,

I wouldn't normally design a 100 ohm system using 50 ohm transmission lines and innerconnects and then compound it with stubs but I was going off your original comment of works meaning no loss of performance. But yes, now that we are no longer constrained by that, it opens the doors to pretty much anything.

I don't see any reason why you'd need 100 ohm cables. You'd replace the bridge (CH0) and pad (CH1) components to make it 100 ohms, the short cable to the T would make some difference, but at 900 MHz (top of band for stock NanoVNA) that would be a few cm at most and not a huge impedance transformation. The "mismatch" such as it is would would come out in the calibration.

It kind of depends on "how important is it that the VNA present a 50 ohm impedance to the DUT"

and a tradeoff against performance.
You could use a 3dB broadband splitter (but probably lose bandwidth) instead of a 6 dB resistive divider (or a T and two 50 ohm resistors)

The transfer relay isn't a panacea - 80dB is typical isolation. The HP VNA test sets use a pair of SPDTs and switch only the source, which probably has better isolation.

If you're measuring systems where you need 80 dB SNR, I suspect that *any* scheme is going to need some special care.

Most software implementations expect arguments to trig functions in radians while most calculators expect degrees.? If you use GNU Octave, there are now functions for either.? sin(theta) expects that theta will be expressed in radians.? sind(theta) expects theta in degrees and so on for the other trig functions and inverse trig functions.

Maynard Wright, W6PAP

In my original post, I had not considered using different stub lengths. That's a good twist. 100 ohm cable and connectors may pose a problem. It seems like the definition of works has changed to reduced performance. "No reason it won't work - at least to the performance of the NanoVNA."

If the mismatches are no problem, the home made transfer relay gets more interesting. Getting one to work at lower frequencies with minimal leakage shouldn't be too costly.

On 10/16/21 2:01 AM, tuckvk3cca wrote:

You can convert the magnitude and phase of S11 under one port measurements to R + jX which might be more useful for you. I forgot the formulas now.

rho = 10^(mag S11/10)

gamma = rho * cos(phase) + j * rho * sin(phase)

Z = Z0 * (1+gamma)/(1-gamma)

if you are doing it in Excel

rho = 10^(S11/10)

gamma=COMPLEX(rho*COS(phase*PI()/180),rho*SIN(phase*PI()/180))

Z =IMPRODUCT(Z0,IMDIV(IMSUM(1,gamma),IMSUB(1,gamma)))

R = IMREAL(Z)

X = IMAGINARY(Z)

The version of the nanoVNA that I have allows me to display the smith chart values in various different formats, including R + jX.

I made a video on this last night and uploaded to YouTube.



As always, if I have made an error or perhaps have demonstrated that I don’t quite understand something, please let me know so I can correct it :-)

--
VE6WGM

On Sat, Oct 16, 2021 at 02:01 AM, tuckvk3cca wrote:

You can convert the magnitude and phase of S11 under one port measurements to
R + jX which might be more useful for you. I forgot the formulas now.

NanoVNA can show R + jX on Smith chart (use MARKER->SMITH VALUE option for select Smith display data format)
Or use Display->Format->Resistance Display->Format->Reactance

You can convert the magnitude and phase of S11 under one port measurements to R + jX which might be more useful for you. I forgot the formulas now.

On 10/15/21 7:20 PM, Roger Need via groups.io wrote:

On Fri, Oct 15, 2021 at 05:50 PM, Jim Lux wrote:

On 10/15/21 5:13 PM, N2MS wrote:

Roger,

My NanoVNA-H4 presently has the following calibrated and saved

configurations.

Recall 0 50kHz-900MHz
Recall 1 1MHz-31MHz
Recall 2 1MHz-61MHz
Recall 3 100MHz-200MHz

If I want to use NanoVNA Saver in the range is it sufficient to

load Recall 0 or do I have to load Recall 2 before running NanoVNA Saver? Do
the calibrated ranges have to match?

Nope.. You can probably just turn it on (which recalls 0) and go from that.

Jim ,

If he is calibrated on 50 KHz. to 900 MHz. and then sets the NanoVNA Saver to 1 1MHz-61MHz. there will be a lot of interpolation going on. Why not recall 2 and avoid
this?

I would assume you'd do a cal in NanoVNA-Saver - the idea behind the "rough wideband cal" is to make sure you're not sending data to NanoVNA-Saver that it doesn't like.

On Fri, Oct 15, 2021 at 05:50 PM, Jim Lux wrote:

On 10/15/21 5:13 PM, N2MS wrote:

Roger,

My NanoVNA-H4 presently has the following calibrated and saved

configurations.

Recall 0 50kHz-900MHz
Recall 1 1MHz-31MHz
Recall 2 1MHz-61MHz
Recall 3 100MHz-200MHz

If I want to use NanoVNA Saver in the range is it sufficient to

load Recall 0 or do I have to load Recall 2 before running NanoVNA Saver? Do
the calibrated ranges have to match?

Nope.. You can probably just turn it on (which recalls 0) and go from that.

Jim ,

If he is calibrated on 50 KHz. to 900 MHz. and then sets the NanoVNA Saver to 1 1MHz-61MHz. there will be a lot of interpolation going on. Why not recall 2 and avoid this?

Mike - N2MS - Try both ways and see how they compare when measuring something like an antenna.

Roger

On 10/15/21 5:13 PM, N2MS wrote:

Roger,

My NanoVNA-H4 presently has the following calibrated and saved configurations.

Recall 0 50kHz-900MHz
Recall 1 1MHz-31MHz
Recall 2 1MHz-61MHz
Recall 3 100MHz-200MHz

If I want to use NanoVNA Saver in the 1Mhz-61MHz range is it sufficient to load Recall 0 or do I have to load Recall 2 before running NanoVNA Saver? Do the calibrated ranges have to match?

Nope.. You can probably just turn it on (which recalls 0) and go from that.

6 to 8 MHz and the center is 7.1 MHz.

Roger,

My NanoVNA-H4 presently has the following calibrated and saved configurations.

Recall 0 50kHz-900MHz
Recall 1 1MHz-31MHz
Recall 2 1MHz-61MHz
Recall 3 100MHz-200MHz

If I want to use NanoVNA Saver in the 1Mhz-61MHz range is it sufficient to load Recall 0 or do I have to load Recall 2 before running NanoVNA Saver? Do the calibrated ranges have to match?

Mike N2MS

On Fri, Oct 15, 2021 at 02:12 PM, Jim Allyn - N7JA wrote:

It is my understanding that you need to do both. The best suggestion I have
seen is to do a broadband calibration and store it in memory 0. You
definitely have to calibrate in NanoVNA Saver.

Jim,

You don't have to calibrate In NanoVNA saver if the NanoVNA is calibrated and you are using the same frequency range in Saver.

Roger