Comments (7)
Hi Joel,
I don't want to teach something that you probably know better than me, but that offset is far too high to justify a bad clock compliance. The nanoVNA uses a good low ppm reference, while the value you reported is on the order of 277.5ppm (!!!), which is worse than any even cheapest xtal on the market.
Are you doing the pragmatic measurements for a xtal by means of a VNA?
In case you don't, take a look at this nice VE6WGM's video :
https://www.youtube.com/watch?v=rVIHVi-7brs
Have a great day
Massimo - IK1IZA
from nanovna-h.
Hi Massimo,
Thank you for the reply =)
Yes, I have done quite a bit reading on using the nanoVNA to profile xtals. In general, I found this method comparison a better video, as it illustrates ways to verify results.
https://www.youtube.com/watch?v=G9zZRNzhsEE
Like yourself, I was rather surprised at the ppm error I ran into. Initially, I thought the manual method I used was in error, grabbed the wrong hc49, or maybe my test jig was wrong. I also tried debugging a little script the community is working on to help improve the laborious matching process, and a similar error occurs with several vendor xtal samples (all report low and within 200ppm).
It should be noted that the crystals will always read low as most manufactures will stamp the devices with slope transition between the series and parallel resonance markers of the xtal, My readings are only off by around 600Hz or so lower than expected. ;-)
What signal should we expect if the stimulus output is set to sweep 10.0MHz to 10.0MHz?
(i.e. if your unit reports higher than mine, than I may have to probe my PCB oscillator is near 26MHz. if that checks out, than I can roll back to an earlier stable firmware to exclude a possible bug. A version recommendation would be appreciated.)
Cheers,
Joel
VE7NTP
from nanovna-h.
Hi Joel,
I'm not sure, what do you mean with: "What signal should we expect if the stimulus output is set to sweep 10.0MHz to 10.0MHz?"
Is that a zero span scan?
Anyways, the resonating frequency of a xtal depends upon the capacitive loads applied to its terminals, referring to the following link second drawing, the xtal load capacitance "pulls" the resonating frequency between Fs and Fa (a little less indeed, otherwise the oscillator could stop or never start oscillating, of course)
https://www.microsemi.com/blog/2016/12/15/crystal-pullability-series-vs-parallel-resonant-crystals/
For that reason it is possible, if not probable that the nominal frequency of the xtal you are measuring is obtained with a specific load capacitance applied at its terminals and the ground.
Usually xtals for logic oscillators need those capacitances in the range of 10 to 40pF to get the nominal frequency marked on them.
Could it be that your issue?
Have a great day.
Massimo - IK1IZA
P.S.
I hope I've been clear above, I apologize for my English.
from nanovna-h.
By the way,
take a look at this this Keysight application note:
http://literature.cdn.keysight.com/litweb/pdf/5965-4972E.pdf
In last paragraph figure 13, you can see a specific xtal test fixture to get accurate measurements by null all the parasitic behaviors of the cables, since very low capacitance can offset the xtal resonance.
from nanovna-h.
"I'm not sure, what do you mean with: "What signal should we expect if the stimulus output is set to sweep 10.0MHz to 10.0MHz?"
Is that a zero span scan?"
Yes, I can measure the single frequency output against a very precise reference. However, VCO/PLL frequency synthesis are never perfect, and knowing what it should be helps. i.e. if it is my 50ohm strip-line measurement setup, than the approx 10MHz read with your scope or counter will still match my nanoVNA output. Removes a lot of variables.
Thanks again for the links, I will read them when I get home.
Your English is still much better than my Italian... ;-)
73
VE7NTP
from nanovna-h.
Hi Joel,
now I'm at my home workshop and I made what you said, that is I connected a SMA T to the S11 port and to my Rohde & Schwarz SME generator driven by my DGPSO system on the symmetric port of the T, then I connected the nanoVNA S21 port to the third T connection via a short cable. I set the nanoVNA to 10MHz CW and the generator to 10.000100MHz and I adjusted the generator level to get the maximum beat on the nanoVNA S21 trace. Then I tuned the generator for the lowest beat frequency (that is for the slowest up and down trace movement).
My nanoVNA reported the minimum frequency beat at -0.2ppm (9.999998MHz)
My nanoVNA H4 reported the minimum frequency beat at +0.7ppm (10.000007MHz)
Hope this could help you.
Have a nice day.
Massimo - IK1IZA
from nanovna-h.
You can calibrate nanoVNA XTAL, if nano know real internal XTAL frequency - it allow correct output.
Now go to
CONFIG->EXPERT SETTINGS->TCXO and set default 26MHz
Set CW freq to 26MHz, wait while device warm up (near 5-10min) measure output frequency.
CONFIG->EXPERT SETTINGS-> TCXO and iput this freq.
After need save config (CONFIG->SAVE)
After this correction NanoVNA CW output must be equal as enter (exist only ~1-2Hz drift, and while device warmup near 10-20Hz)
from nanovna-h.
Related Issues (20)
- Connect NanoVNA-H to Windows 7 Machine and Assign COM Port HOT 1
- could not open the screenshot bmp file. HOT 2
- 1.1.01 : Toggling to mode SI5351 does not stay set between reboots. HOT 2
- Marker Search Values are incorrectly saved to calibration when Tracking is ON
- Can't compile for target F072 (cannot move location counter backwards) HOT 14
- Enhancement Calibrate, Power in dBm
- Avoid releasing non-x.x.x versions
- How to calculate the values of resistive return loss bridge?
- Add a mode to measure Common Mode Current Chokes
- Black screen on boot and failure to save anything to SD with 1.2.14 code HOT 2
- which file HOT 1
- Not proceed.
- NanoVNA-H4 Hanging on scan
- Can someone confirm 1.2.14 COM port comms is working? HOT 1
- NanoVNA-H v 1.2.14 - SWR scan freezes for a second or two every so often. HOT 4
- NanoVNA H4 does not starts HOT 1
- New version no longer has AA like in 2020 HOT 1
- Menu on right does not work HOT 1
- How to read an write flash/firmware with Linux ?
- VNAViewer Version for Linux that is Compatible with this Firmware ?
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from nanovna-h.