¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. Nanovna-Users
  2. Messages
Expanded Topics Messages
Date
Re: characteristic impedance

 

On Sun, Jan 26, 2020 at 04:51 AM, Andy UA3RAW wrote:

Herb, it seems to me that a half-way around the smith chart is 1/4 wave length. Isn't it? )))

=========================================================================

Andy,
You may be able to put it in better terms than I did, as I was only parroting back what I understood from the original poster. I have only used smith charts sparingly in my career. The key thing that stuck in my mind was the original poster saying the 1/8 method started from the same position as a short on the first revolution around the smith chart.

Since the actual method has always worked for me I didn't give it any deeper thought. If the terminology I used needs correcting please add to the discussion so I can correct my notes and not perpetuate incorrect information (i.e. if that point is 1/4 wave length why is it called the 1/8th method).

- Herb
Re: nanovna-users]NanoVNA-H4 2Port calibrationof

 

Oristo,

Thanks for your information abt. the serial port, actually I am using a version 3.1 comport and sofar I saw no problems in comunicating with theNano VNA-H4 , with the firmware as supplied by Alibaba.

This problem was sollved by executing a new device stand alone calibration and saving it to CH0 of the device.

Best Regards

Jos

Op 26-1-2020 om 14:03 schreef Oristo:

it appears that at start NanoVNA-Saver is using the C0? calibration of
Yes
NanoVNA, untill now I thought these calibrations were independant.
No, USB serial communication from nanoVNA to Python is not reliable for
all firmware, USB cables and versions of Python.
Using a USB 2.0 (rather than 3.0) port e.g. by hub sometimes helps.
Adding ferrite beads to USB cable may help.
Some firmware and Python serial implementations are simply flakey.
Rune's workaround is to depend on nanoVNA C0 calibration returning data values nearly correct.
Re: nanovna-users]NanoVNA-H4 2Port calibrationof

 

On Sun, Jan 26, 2020 at 04:38 AM, Jos Stevens wrote:

"This is an eye opener for me, it appears that at start NanoVNA-Saver is using the C0 calibration of NanoVNA, untill now I thought these calibrations were independant."

- It always helps to get a different perspective from someone else. Especially true when you are doing everything "right" and you still get unexplainable results.

"I just made a new 100 Segs calibration. Please see the attached results."

- Your after calibration thru results are definitely on the money.

" NanoVNA-H4 is a great device, just the CH1 impedance could be a bit better and the enclosed 50 Ohms standard I measure (4 point measurement @ 10kHz) 50.940 Ohms, also could be a bit better, I use one that I previously received wich I measure 49.850 OHms and correct it in NanoVna-Saver's "Calibration" window. Yes I can do that for the portsavers also."

- For $60 usd delivered via parcel post, you can't expect too much better quality than what is already in the package. The terminator actually measures better than some name brand units I have, and the return loss is very well behaved. I always keep in mind that hugen developed the NanoVNA to "to attract more young people to pay attention to radio frequency and wireless" and that tempers my expectations regarding any meteorologist level performance. The volume of sales world wide over the past few months indicates he not only has attracted some youngsters to RF measurement techniques, but given some of us older people access to measurement capability that we previously lacked.

Regards,

- Herb
Re: Clear config NanoVNA

 

Thx for the info !

Hans
Re: nanovna-users]NanoVNA-H4 2Port calibrationof

 

it appears that at start NanoVNA-Saver is using the C0? calibration of
Yes
NanoVNA, untill now I thought these calibrations were independant.
No, USB serial communication from nanoVNA to Python is not reliable for
all firmware, USB cables and versions of Python.
Using a USB 2.0 (rather than 3.0) port e.g. by hub sometimes helps.
Adding ferrite beads to USB cable may help.
Some firmware and Python serial implementations are simply flakey.
Rune's workaround is to depend on nanoVNA C0 calibration returning data values nearly correct.
Re: First PCB pictures of the V2

 

MAX2870. Maxim has an oscillator chip MAX2870, which gives from 23MHz to 6GHz. Digikey says it costs 10?€$ whatever. I know this is too late for this version but maybe in the future, and then there are probably new chips available.
Re: characteristic impedance

 

On Sun, Jan 26, 2020 at 11:46 AM, hwalker wrote:
2. I set <marker 1> to half-way around the smith chart (1/8 wave length) and
- Herb
Herb, it seems to me that a half-way around the smith chart is 1/4 wave length. Isn't it? )))
Re: nanovna-users]NanoVNA-H4 2Port calibrationof

 

Herb,

This is an eye opener for me, it appears that at start NanoVNA-Saver is using the C0? calibration of NanoVNA, untill now I thought these calibrations were independant.

I just made a new 100 Segs calibration. Please see the attached results.

NanoVNA-H4 is a great device, just the CH1 impedance could be a bit better and the enclosed 50 Ohms standard I measure (4? point measurement @ 10kHz) 50.940 Ohms, also could be a bit? better, I use one that I previously received wich I measure 49.850 OHms and correct it in NanoVna-Saver's? "Calibration"? window. Yes I can do that for the portsavers also.

Best regards,

Jos

Op 26-1-2020 om 01:24 schreef hwalker:

On Sat, Jan 25, 2020 at 03:58 PM, Jos Stevens wrote:

I did what you suggested , removed the portsavers re-calibrated the standalone VNA,the result was better then before 0.00 db, +0.12 and -0.25 at 50k, 750M and 1500M. Then I calibrated in Nanovna-Saver using 4 segs like you, Before was better, and After was an ideal straight line at 0 dB!

==============================================================================

Good job Jos. I initially had problems with Rune's calibration module but after he posted that you needed to start the module from a good calibration on the NanoVNA saved to "SAVE 0" it has always worked well for me. I still use the ideal models because I hate entering numbers that I don't fully understand.

Rune's NanoVNA-saver application has been working great with the NanoVNA-H4 thus far. The screen saver doesn't work because different code is required for the 4" display, and NanoVNA-saver reports the unit as a NanoVNA-H which may mean the hugen will need to change the -H4 identifier in firmware to help developers differentiate it.

- Herb

-=-=-=-=-=-=-=-=-=-=-=-

Smith before calibration 100 segs.png
Smit after 100 Segs calibration with portsavers.png
S21 With portsavers. before caluibration 100 Segs.png
S21 With portsavers after calibration .png

Re: nanovna-users]NanoVNA-H4 2Port calibrationof

Eric Furness
 

On 1/25/2020 3:37 PM, Jos Stevens wrote:
Hi Oristo and Herb,

Thinks for the pictures Oristo, i think they are from the 2.8" NanoVNA-H, my 2.8 -H version works well, this problem is? with my VNA new version H4.

Herb,? yes I did use the calibration wizard and I have done it so often that I can do it blindfolded..

The only thing different is that For the H4 I used portsavers and used one of the cables that were in the box of the -H4, the firmware is still from the first of Januari 2020, I did not upgrade yet because I learned that there are problems with the new firmware.

Anyhow you say that you have no problems,? I'm using NanoVNA-Saver 0.2.2.1, the latest version as far as I know. I hardly can believe that the problem is in the hardware, because the hardware stand alone shows "Ch1 Logmag 10 dB/-1.42 dB @ 50 kHz" , -0.07 dB @ 810Mhz and -1.55 dB @ 1500 MHz after a 101 point calibration. A minute ago I ran the calibration again on NanoVNA-Saver and attached the pictures before and after pressing "Apply".

What can I do more ?

Jos
The RG174 jumpers that came with my Nano were very noisy.? I bought a kit of 5 teflon cables, now cal works good and no more noise.
Eric WA3UYI
Re: problems with SWR reading in nanovna-h v3.4 #measurement #calibration #nanovna-h_v3dot4

 

Oristo, thanks a lot! I will try and let you know, best,
°ä¨¦²õ²¹°ù.
Re: Wireless control of NanoVNA

 

If the NanoVNA had a WiFi transceiver on board in addition to the USB port, so
it could be controlled remotely by NanoVNA Sharp, NanoVNA Saver, or similar
applications.
If nanoVNAs had BlueTooth, then they could also be controlled by iOS apps.
There are fairly cheap BlueTooth modules with programmable microcontrollers
and also fairly cheap USB host shields.
Firmware integrating those for a dongle could work for all nanoVNAs, not just H4s..
Re: characteristic impedance

 

the 1/8 wave method
added to /g/nanovna-users/wiki/Application-Notes#Collected-wisdom
Re: Clear config NanoVNA

 

Hi Hans -

and advise is clear "config"
see /g/nanovna-users/message/10215

Is calibration also required ?
It will be, after clearconfig
Re: problems with SWR reading in nanovna-h v3.4 #measurement #calibration #nanovna-h_v3dot4

 

Before all that, check for SMA connector integrity.
Re: problems with SWR reading in nanovna-h v3.4 #measurement #calibration #nanovna-h_v3dot4

 

Hi Cesar -

I suppose that your issues are related,
and I suggest that the problem is/was corrupted calibration data area
which has been my experience with first calibrations with some new firmwares.

The workaround:
----------------------
Using a serial terminal program to communicated with nanoVNA's USB virtual COM port
(e.g. PuTTY )
invoke the console shell command `clearconfig 1234`
/g/nanovna-users/files/NanoVNA_Console_Commands_Dec%209-19.pdf
then power off and back on
then recalibrate the touch panel using touchcal and touchtest
/g/nanovna-users/message/7759
perhaps check vbat and tweak by vbat_offset
/g/nanovna-users/message/6549
/g/nanovna-users/message/9868
then saveconfig

then, by touchscreen menu CAL->RESET

then CAL->CALIBRATION
/g/nanovna-users/message/7759
/g/nanovna-users/message/7810
Re: Cheap calibration loads #parts

 

Thanks Herb for confirming my suspicion.

I've looked at the specs once again: VSWR: 1.05 + 0.008 f (GHz) max @ DC - 18.0 GHz, 1.30 max @ 18 - 26.5 GHz
so I would expect 1.30 at frequencies above 18GHz, which is not my case.

PS: I did compare with Radiall SMA terminators rated up to 4GHz and I don't see such behaviour at low frequencies.
Re: Full reflection runs over the perimeter of the smith chart

 

Hello Rudi,
hello Oristo,
thank you very much for your reply!
If I use i.e. RG58 with a length of abt. 1m I don't see the problem as well due to the high loss of this cable (RG58 1m.jpg). But if you take a low loss coax cable like RG402 ( RG402 semi rigid.jpg) you will see the quality of your calibration standard settings. The expert Kurt Poulsen, is working the issue, and I am confident that he will solve it.

Best regards
Norbert, DG1KPN

RG58 1m.jpg
RG402 semi rigid.jpg

problems with SWR reading in nanovna-h v3.4 #measurement #calibration #nanovna-h_v3dot4

 

Hi all,

I just got my NanoVNA-H 3.4 (official version via alibaba/Maggie). Generally it works quite well, but I find two issues:
1) SWR reading shows always 1 across the entire sweep range, from 50kHz up to 900MHz, regardless of what DUT is at the port, even for open, short, always I get a flat SWR=1. Any idea how to solve this? shall I try firmware update? and if so which version do you recommend?
2) another less important issue is with the calibration. It seems quite difficult with my unit to calibrate the open port. After the full SOL calibration, I always check again each S, O and L, typically Short and Load are OK, but Open is quite off, generally in the capacitive region.
Apologize if these topics have been discussed already in any other thread, if so I was unable to find them in this group.
Any hint will be wellcome! thanks,

C¨¦sar, EA5IOQ
Clear config NanoVNA

 

Hello all,
Just flashed firmware 0.60 by Edy555 in my NanoVNA ( ) and advise is clear "config" NanoVNA.
I searched in the menu and manual of the NanoVNA but i can't find it.

Is calibration also required ?

Thanks in advance !

Hans
Re: characteristic impedance

 

On Sat, Jan 25, 2020 at 10:01 PM, Bob Albert wrote:

"... When I measure 50 Ohm coaxial impedance with the 1/8 wave method, I always get 50 Ohms. I tried some 75 Ohm cable and still get 50 Ohms!.."
=====================================================================
Bob,
I haven't tried the 1/8 wave method with my NanoVNA-H4 yet so your question gave me a reason to do so. See the attachment for details.

1. I connected a 2 mtr length of RG-59 (75 ohm) cable to CH0. My calibrated range was 50k-1G and I reduced the stop frequency until I had one full revolution of the smith chart.

2. I set <marker 1> to half-way around the smith chart (1/8 wave length) and read the frequency (24 MHz)

3. I set <marker 2> to half that frequency (~12 MHz) and read the impedance (~75 ohms).

I could not set my second marker to exactly 12 MHz because my original calibration points landed me on either side of that frequency. One side was 76.4 ohms and the other side was 73.2 ohms. If I had done a 101 point cal from 50k-50M I could have landed on 12 MHz (~75 ohms).

I've used this method since it was introduced to the group and its always worked for me.

- Herb

2mtr_RG-59_Z.png

29641 - 29660 of 39713