Topics

Review of S-A-A-2 #nanovna-v2


hwalker
 

I flipped a coin about three weeks ago and ordered an S-A-A-2 (NanoVNA-V2) analyzer for our ham club. We already had one the other three variations (-H_v3.4, -H4 and -F) and have been very satisfied with their price to performance ratio. Adding the -V2 for testing above 2 GHz was an easy decision. The -V2 arrived today - about the same time as some other members have reported receiving their units.

The NanoVNA-V2 was $65 usd from Tindie, including shipping. Tindie filled the order promptly after receiving my PayPal payment, but then the shipment was stuck in transit at the Shanghai postal depot for over a week - most likely due to COVID-19 delays. Given the circumstances, 3-weeks for delivery was understandable. As of this writing Tindie is out of stock. There are two eBay sellers of the NanoVNA-V2, but they both are asking more than double the Tindie store price (no thanks!).

The NanoVNA-V2 was developed by OwOComm under the design leadership of Gabriel Tena-White. Gabriel is well known and respected in the on-line technical community. OwOComm originally developed a VNA, let's call it the S-A-A-1, prior to the release of the NanoVNA without a display and a top end frequency of 300 MHz. Before it could be manufactured, hugen's NanoVNA burst on the retail scene with display, a top end frequency of 900 MHz, and priced below $100. OwOComm met with its client and they decided not to manufacture the S-A-A-1 and instead started on a new development called the S-A-A-2. OwOComm does not sell or manufacture the NanoVNA-V2. Sales and support are by the HCXQS group. HCXQS does not have a technical support forum or GitHub page that I could locate. Their initial production run of NanoVNA-V2's appears to have been about 150 units (Tindie reported 144 orders before posting their out of stock notice).

Un-wrapping:

The NanoVNA-V2 came in a small cardboard box and was packed in bubble wrap, no accessories included. The packing was sufficient to survive the 3-week land-air-land journey.

The contents of the storage box included:
NanoVNA-V2 (with no battery) Note: developer recommends 1000-2000 mAh Li-On batt, 6 x 40 x 60 mm, connector: JST-XH 2.54mm.
No USB cable (micro USB data cable required for connecting to PC).
No SMA RF cables (RG316, SS405, or RG405 cables recommended by designer).
No SMA calibration kit.
No SMA female to female connector for through calibration.

If you don't already have any of the above accessories you will need to account for their cost in the overall purchase price of the NanoVNA-V2. My unit arrived un-calibrated and would not have been useable if I didn't already have a calibration kit.

Immediate visual impression compared to the original NanoVNA

The original 2.8" NanoVNA did not have a case and its power switch and multi-function thumb-wheel switch felt a bit flimsy. Subsequent -H and -H4 models have an ABS case that provide guards for the side mounted port connectors; additionally, the -H4 has better quality switches.

The appearance of the NanoVNA-V2 harkens back to the original 2.8" NanoVNA. It has two PCB's sandwiched between standoffs with a 2.8" display on top. The multi-function thumb-wheel switch has been replaced by three small push button switches. The push-button switches were placed between the SMA connectors so users designing a protective case will need to be imaginative. The PCB version is marked as SAA V2_2.

The NanoVNA-V2's 2.8" display will be a disappointment to user's hoping for a larger display. My understanding from past posts by Gabriel (the board designer) is that a drop-in 3.2" display is available for user upgrade. The on-screen layout of the display will be immediately familiar to anyone who has used a previous NanoVNA variant. The display firmware seems to be based on edy555's ver 6.0 firmware.

PC Software:

None of the current PC software (NanoVNA-saver, NanoVNA-Sharp, TAPR, WebApp) work with the NanoVNA-V2. Rune has ordered a NanoVNA-V2 and has indicated that he intends to support the device in NanoVNA-saver. Erik has also indicated that TAPR may support the NanoVNA-V2. The NanoVNA-V2 has a native PC program called NanoVNA-QT Software. It is a port from an open source VNA program and some functions are not relevant to the NanoVNA-V2.

I downloaded the USB-Serial port driver and NanoVNA-QT software from, https://github.com/nanovna/NanoVNA-QT/releases . There are installations for Windows (7+) and Linux. The Mac OS is not supported - yet. On Windows you have to load the driver package first. This went smoothly for me on Windows 10. The archive for NanoVNA-QT should be un-zipped to a desired directory and then the executable in the directory can be run without any install required.

Using NanoVNA-QT is different than NanoVNA-Saver and takes some getting used to. It seems to have most of the features you would expect from this type of software and connected to the -V2 without issue - once the correct COM port was selected. From within the program you can perform up to 1024 point sweeps, which eclipses the 201 point maximum sweep on the device. Overall the program gives a good first impression, and for updating the firmware of the NanoVNA-V2 is the only available option.

NanoVNA-V2 does not support terminal commands. I find it nice when using the NanoVNA to load up a terminal program and type in console commands to remotely program the device. The design of the NanoVNA-V2 does not support doing this. Gabriel indicated that a python class might possibly be ready when the V-2 was launched, but I was unable to use the one at https://github.com/nanovna/NanoVNA-V2-firmware, at least not in the way I use the class for the NanoVNA.

While the V-2 is connected to NanoVNA-QT, the display is blanked with a version message. When I closed the NanoVNA-QT program, I couldn't find a way of restoring the display for manual use without cycling power.

In Use:

Turning on the NanoVNA-V2 presented a version screen of NanoVNA V2_2 Jan 18 2020. I checked the NanoVNA-V2 GitHub site for newer firmware releases but none were posted. You'll want to take care of what operations you perform until back-up firmware becomes available. Updating the firmware, as previously noted requires NanoVNA-QT. STM DfuSeDemo utility is a thing of the past.

The specified NanoVNA-V2 frequency range is 50kHz - 3GHz, but as reported previously by Wolfgang, the top measurement frequency can be set to 4.5 GHz- with good performance to 3.5 GHz. The V-2 operates only using fundamentals and does not use harmonics for higher ranges as the other NanoVNA variants do. The waveforms from the two V-2 synthesizers are not sinusoidal so there are still plenty of harmonics in the output spectrum, but unlike the NanoVNA, you don't have base frequencies higher in amplitude than the signal you are generating.

The menu structure for the NanoVNA-V2 mimics that of the NanoVNA. Calibration, Trace, Sweep and Marker settings all work the same. There are a couple of new options for setting the number of display points, and flipping the display orientation.

Under the hood:

The NanoVNA-V2 is powered by a GD32F303CCT6 processor. It has 48KB of SRAM and 256KB of flash memory which is comparable to the NanoVNA-H4.

Published specifications are:
Frequency range: 50kHz - 3GHz
System dynamic range (calibrated): 70dB (up to 1.5GHz), 60dB (up to 3GHz)
S11 noise floor (calibrated): -50dB (up to 1.5GHz), -40dB (up to 3GHz)
Sweep rate: 100 points/s
Display: 2.8'', 320 x 240
USB interface: Micro USB
Power: USB, 300mA
Battery: not included. Includes charging circuitry.
Maximum sweep points (on device): 201
Maximum sweep points (USB): 1024
VNA-QT software supported platforms: Linux, Windows (7+), Mac OS planned

Since the device arrived un-calibrated, the first order of business was to perform an OSLT cal. There were a few differences noted from the normal NanoVNA OSLT calibration. The first was that there is no isolation step. The second is the save step does not change the display notation to the saved channel (i.e. saving to location 0 did not change the notation to C0). The third was that cycling power did not automatically recall save location 0. The display always comes up in the un-corrected state and you have to manually recall 0 from the "RECALL" menu, at that point the C0 notation is displayed.

I purchased a 1 - 2GHz BPF that I have been meaning to test and it seemed like a good candidate for the NanoVNA-2. The attached photo shows the filter measured from 20 MHz to 3 GHz. The filter skirts and band pass are as specified by the manufacturer.

The NanoVNA-V2 is a welcome addition to my club's test instrumentation. Judging by comments from some NanoVNA-H owners, the 2.8" display is going to be a disappointment. If you can get by the display size and judge the NanoVNA-V2 on its performance and cost, you will be hard pressed to find a comparable 3 GHz device.



- Herb


Dallas KD4HNX
 

Herb,
First I want to thank you for such a detailed report/review of the S-A-A-2.
I'm looking to purchase my first NanoVNA and I'm overwhelmed by which one to get.
By chance have you done reviews of the other VNAs your club has purchased?  If so I'd love to read them...


73 Dallas, KD4HNX
Whatever you do, don’t fall victim to “paralysis by
analysis.” Go ahead and buy/build one and start 
tinkering with it. This is a learn by doing hobby.

No politician or scholar assured your freedoms.
A Soldier, Sailor, Marine, or Airman did!

On Friday, March 27, 2020, 10:10:29 PM EDT, hwalker <herbwalker2476@...> wrote:

    I flipped a coin about three weeks ago and ordered an S-A-A-2 (NanoVNA-V2) analyzer for our ham club.  We already had one the other three variations (-H_v3.4, -H4 and -F) and have been very satisfied with their price to performance ratio. Adding the -V2 for testing above 2 GHz was an easy decision. The -V2 arrived today - about the same time as some other members have reported receiving their units.

    The NanoVNA-V2 was $65 usd from Tindie, including shipping.  Tindie filled the order promptly after receiving my PayPal payment, but then the shipment was stuck in transit at the Shanghai postal depot for over a week - most likely due to COVID-19 delays. Given the circumstances, 3-weeks for delivery was understandable. As of this writing Tindie is out of stock. There are two eBay sellers of the NanoVNA-V2, but they both are asking more than double the Tindie store price (no thanks!).


hwalker
 

On Sat, Mar 28, 2020 at 04:10 AM, Dallas KD4HNX wrote:

I'm looking to purchase my first NanoVNA and I'm overwhelmed by which one to get. By chance have you done reviews of the other VNAs your club has purchased? 
==============================================================
Dallas,
You might want to check the review I did of the NanoVNA-H4 at https://groups.io/g/nanovna-users/message/10012 .

As a first time buyer I would limit my choices to the NanoVNA-H ver3.4, NanoVNA-H4, NanoVNA-F or S-A-A-2. The NanoVNA-H ver3.4 has the latest board modifications by hugen and limited measurement capability approaching 2 GHz. It is also the most supported version by firmware developers. Its drawbacks are a 2.8" display, slower processor, and limited flash memory. Almost all current software supports it.

The NanoVNA-H4 also has hugen's latest board modifications and limited measurement capability approaching 2 GHz. The 4" display is an improvement over the NanoVNA-H and it has more flash memory space and a faster processor. It should be more future proof than the NanoVNA-H. It is not as well supported by firmware developers as the NanoVNA-H. Currently hugen is the only developer with official firmware releases for the NanoVNA-H4. Almost all current software supports it. It is a fairly new product and problems with the case fitting has been reported by some users.

The NanoVNA-F has the best display of the NanoVNA variants. It is a 4.3" display with about twice the resolution of the NanoVNA-H4. It has more flash memory space and a faster processor than the NanoVNA-H which should make it more future proof. It has a metal housing versus the ABS housing of the NanoVNA-H v3.4 and NanoVNA-H4. It is not as well supported by firmware developers as the NanoVNA-H. Currently BH5HNU is the only developer with official firmware releases for the NanoVNA-F. Almost all current software supports it. The most current versions are 2.3 (Thumb wheel switch) and 3.1 (Push button switches). Older 2.2 versions are available at a discounted price, but have more limited capability than the newer versions.

The S-A-A-2 (NanoVNA-V2) is the only game in town if you want to make measurements up to 3 GHz (fairly good to 3.5 GHz). Its 2.8" display, lack of accessories, no protective housing, no battery and limited software/firmware support are its primary negatives. It currently has limited availability as its first production run was sold out within a month. Subsequent production runs may address some of the negatives I mentioned.

- Hope that helps.

- Herb


Larry Rothman
 

Great write-up Herb!
Does the V2 have the port available for using an ST-link for flashing?



On Fri, 27 Mar 2020 at 10:10 PM, hwalker<herbwalker2476@...> wrote:     I flipped a coin about three weeks ago and ordered an S-A-A-2 (NanoVNA-V2) analyzer for our ham club.  We already had one the other three variations (-H_v3.4, -H4 and -F) and have been very satisfied with their price to performance ratio. Adding the -V2 for testing above 2 GHz was an easy decision. The -V2 arrived today - about the same time as some other members have reported receiving their units.

    The NanoVNA-V2 was $65 usd from Tindie, including shipping.  Tindie filled the order promptly after receiving my PayPal payment, but then the shipment was stuck in transit at the Shanghai postal depot for over a week - most likely due to COVID-19 delays. Given the circumstances, 3-weeks for delivery was understandable. As of this writing Tindie is out of stock. There are two eBay sellers of the NanoVNA-V2, but they both are asking more than double the Tindie store price (no thanks!).

    The NanoVNA-V2 was developed by OwOComm under the design leadership of Gabriel Tena-White. Gabriel is well known and respected in the on-line technical community. OwOComm originally developed a VNA, let's call it the S-A-A-1, prior to the release of the NanoVNA without a display and a top end frequency of 300 MHz.  Before it could be manufactured, hugen's NanoVNA burst on the retail scene with display, a top end frequency of 900 MHz, and priced below $100. OwOComm met with its client and they decided not to manufacture the S-A-A-1 and instead started on a new development called the S-A-A-2.  OwOComm does not sell or manufacture the NanoVNA-V2. Sales and support are by the HCXQS group. HCXQS does not have a technical support forum or GitHub page that I could locate.  Their initial production run of NanoVNA-V2's appears to have been about 150 units (Tindie reported 144 orders before posting their out of stock notice).

  Un-wrapping:

    The NanoVNA-V2 came in a small cardboard box and was packed in bubble wrap, no accessories included.  The packing was sufficient to survive the 3-week land-air-land journey.

    The contents of the storage box included:
      NanoVNA-V2 (with no battery) Note: developer recommends 1000-2000 mAh Li-On batt, 6 x 40 x 60 mm, connector: JST-XH 2.54mm.
      No USB cable (micro USB data cable required for connecting to PC).
      No SMA RF cables (RG316, SS405, or RG405 cables recommended by designer).
      No SMA calibration kit.
      No SMA female to female connector for through calibration.

      If you don't already have any of the above accessories you will need to account for their cost in the overall purchase price of the NanoVNA-V2. My unit arrived un-calibrated and would not have been useable if I didn't already have a calibration kit.

  Immediate visual impression compared to the original NanoVNA

    The original 2.8" NanoVNA did not have a case and its power switch and multi-function thumb-wheel switch felt a bit flimsy. Subsequent -H and -H4 models have an ABS case that provide guards for the side mounted port connectors; additionally, the -H4 has better quality switches.
     
    The appearance of the NanoVNA-V2 harkens back to the original 2.8" NanoVNA. It has two PCB's sandwiched between standoffs with a 2.8" display on top. The multi-function thumb-wheel switch has been replaced by three small push button switches.  The push-button switches were placed between the SMA connectors so users designing a protective case will need to be imaginative.  The PCB version is marked as SAA V2_2.

    The NanoVNA-V2's 2.8" display will be a disappointment to user's hoping for a larger display.  My understanding from past posts by Gabriel (the board designer) is that a drop-in 3.2" display is available for user upgrade. The on-screen layout of the display will be immediately familiar to anyone who has used a previous NanoVNA variant. The display firmware seems to be based on edy555's ver 6.0 firmware.

    PC Software:

    None of the current PC software (NanoVNA-saver, NanoVNA-Sharp, TAPR, WebApp) work with the NanoVNA-V2.  Rune has ordered a NanoVNA-V2 and has indicated that he intends to support the device in NanoVNA-saver. Erik has also indicated that TAPR may support the NanoVNA-V2.  The NanoVNA-V2 has a native PC program called NanoVNA-QT Software. It is a port from an open source VNA program and some functions are not relevant to the NanoVNA-V2.

  I downloaded the USB-Serial port driver and NanoVNA-QT software from, https://github.com/nanovna/NanoVNA-QT/releases .  There are installations for Windows (7+)  and Linux.  The Mac OS is not supported - yet. On Windows you have to load the driver package first. This went smoothly for me on Windows 10. The archive for NanoVNA-QT should be un-zipped to a desired directory and then the executable in the directory can be run without any install required.

  Using NanoVNA-QT is different than NanoVNA-Saver and takes some getting used to. It seems to have most of the features you would expect from this type of software and connected to the -V2 without issue - once the correct COM port was selected. From within the program you can perform up to 1024 point sweeps, which eclipses the 201 point maximum sweep on the device. Overall the program gives a good first impression, and for updating the firmware of the NanoVNA-V2 is the only available option.
 
  NanoVNA-V2 does not support terminal commands. I find it nice when using the NanoVNA to load up a terminal program and type in console commands to remotely program the device.  The design of the NanoVNA-V2 does not support doing this.  Gabriel indicated that a python class might possibly be ready when the V-2 was launched, but I was unable to use the one at https://github.com/nanovna/NanoVNA-V2-firmware, at least not in the way I use the class for the NanoVNA.
 
While the V-2 is connected to NanoVNA-QT, the display is blanked with a version message. When I closed the NanoVNA-QT program, I couldn't find a way of restoring the display for manual use without cycling power.

    In Use:

    Turning on the NanoVNA-V2 presented a version screen of NanoVNA V2_2  Jan 18 2020.  I checked the NanoVNA-V2 GitHub site for newer firmware releases but none were posted. You'll want to take care of what operations you perform until back-up firmware becomes available.  Updating the firmware, as previously noted requires NanoVNA-QT.  STM DfuSeDemo utility is a thing of the past.

    The specified NanoVNA-V2 frequency range is 50kHz - 3GHz, but as reported previously by Wolfgang, the top measurement frequency can be set to 4.5 GHz- with good performance to 3.5 GHz. The V-2 operates only using fundamentals and does not use harmonics for higher ranges as the other NanoVNA variants do. The waveforms from the two V-2 synthesizers are not sinusoidal so there are still plenty of harmonics in the output spectrum, but unlike the NanoVNA, you don't have base frequencies higher in amplitude than the signal you are generating.

    The menu structure for the NanoVNA-V2 mimics that of the NanoVNA. Calibration, Trace, Sweep and Marker settings all work the same. There are a couple of new options for setting the number of display points, and flipping the display orientation.

  Under the hood:

  The NanoVNA-V2 is powered by a GD32F303CCT6 processor. It has 48KB of SRAM and 256KB of flash memory which is comparable to the NanoVNA-H4.

  Published specifications are:
  Frequency range: 50kHz - 3GHz
  System dynamic range (calibrated): 70dB (up to 1.5GHz), 60dB (up to 3GHz)
  S11 noise floor (calibrated): -50dB (up to 1.5GHz), -40dB (up to 3GHz)
  Sweep rate: 100 points/s
  Display: 2.8'', 320 x 240
  USB interface: Micro USB
  Power: USB, 300mA
  Battery: not included. Includes charging circuitry.
  Maximum sweep points (on device): 201
  Maximum sweep points (USB): 1024
  VNA-QT software supported platforms: Linux, Windows (7+), Mac OS planned
 
  Since the device arrived un-calibrated, the first order of business was to perform an OSLT cal. There were a few differences noted from the normal  NanoVNA OSLT calibration. The first was that there is no isolation step. The second is the save step does not change the display notation to the saved channel (i.e. saving to location 0 did not change the notation to C0). The third was that cycling power did not automatically recall save location 0.  The display always comes up in the un-corrected state and you have to manually recall 0 from the "RECALL" menu, at that point the C0 notation is displayed.
 
  I purchased a 1 - 2GHz BPF that I have been meaning to test and it seemed like a good candidate for the NanoVNA-2. The attached photo shows the filter measured from 20 MHz to 3 GHz. The filter skirts and band pass are as specified by the manufacturer.

  The NanoVNA-V2 is a welcome addition to my club's test instrumentation.  Judging by comments from some NanoVNA-H owners, the 2.8" display is going to be a disappointment.  If you can get by the display size and judge the NanoVNA-V2 on its performance and cost, you will be hard pressed to find a comparable 3 GHz device.



- Herb


DougVL
 

Many, many thanks for the really wonderful comparison of the models.
I have a fairly early model, received in Mid-October, 2019 and hope to move up to a 4 inch model. Your comparison really helps!

Doug, K8RFT


hwalker
 

On Sat, Mar 28, 2020 at 06:45 AM, Larry Rothman wrote:

Does the V2 have the port available for using an ST-link for flashing?
=======================================================
Larry,
That's probably a question for Gabriel. Here's what I see on the accessible connectors ..

CONN303
- SWDIO
- SWIO
- GND
- NRST
- NC

J4
- SD_CLK
- SD_MOSI
- SD_MISO
- SD_CS

S301
- SWDIO
- SWCLK


J4 looks like a connector for future SD card addition. CONN303 and S301 have pins with ST-link like control names.

- Herb


Erik Kaashoek
 

On Sat, Mar 28, 2020 at 06:45 AM, Larry Rothman wrote:


Does the V2 have the port available for using an ST-link for flashing?
Yes, I used CON303 pins connected to ST-Link for updating the SW of my pre-production model to v2.2
All the SW is on github so you can modify, build, updated as you like.

--
NanoVNA Wiki: https://groups.io/g/nanovna-users/wiki/home
NanoVNA Files: https://groups.io/g/nanovna-users/files
Erik, PD0EK


Dragan Milivojevic
 

Schematics, PCB, diagrams etc at: https://gitlab.com/bepissneks/S-A-A

On Sat, 28 Mar 2020 at 16:36, <erik@...> wrote:

On Sat, Mar 28, 2020 at 06:45 AM, Larry Rothman wrote:


Does the V2 have the port available for using an ST-link for flashing?
Yes, I used CON303 pins connected to ST-Link for updating the SW of my
pre-production model to v2.2
All the SW is on github so you can modify, build, updated as you like.

--
NanoVNA Wiki: https://groups.io/g/nanovna-users/wiki/home
NanoVNA Files: https://groups.io/g/nanovna-users/files
Erik, PD0EK




Larry Rothman
 

Good to know there are 3 ways to update the FW. 
Thanks Erik



On Sat, 28 Mar 2020 at 11:36 AM, erik@...<erik@...> wrote: On Sat, Mar 28, 2020 at 06:45 AM, Larry Rothman wrote:


Does the V2 have the port available for using an ST-link for flashing?
Yes,  I used CON303 pins connected to ST-Link for updating the SW of my pre-production model to v2.2
All the SW is on github so you can modify, build, updated as you like.

--
NanoVNA Wiki: https://groups.io/g/nanovna-users/wiki/home
NanoVNA Files: https://groups.io/g/nanovna-users/files
Erik, PD0EK


hwalker
 

A correction to my review of the S-A-A-2. In addition to NanoVNA-QT, erik's last MOD of TAPR v4.6 located at https://groups.io/g/nanovna-users/files/NanoVNA%20PC%20Software/TAPR%20VNA/VNAR4.6.zip . also, supports the S-A-A-2. For some reason my Windows 10 computer was missing a couple of dll's that I had to track down, but once installed TAPR ran fine. An operating manual for TAPR 4.6 is also located at https://groups.io/g/nanovna-users/files/NanoVNA%20PC%20Software/ .

TAPR is currently the only software application that works across all NanoVNA variations.

The S-A-A-2 also goes into USB Mode (white screen with message) when connected to TAPR and after exiting the program, you still have to cycle power on the S-A-A-2 to regain manual control of it.


- Herb


Joe Burkleo
 

Herb,
One thing I have not seen in the spec's so far is what the output level is.

Have you measured that or do you know what it is?

If I remember correctly the original version was in the -10 dbm range.

Thanks,
Joe - WA7JAW


Jim Allyn - N7JA
 

On 3/28/20 10:49 PM, Joe Burkleo wrote:
One thing I have not seen in the spec's so far is what the output level is.
     At lower frequencies, the NanoVNA 2.0 uses the same chip as the version 1, an Si5351.  So, the output level will probably be similar.  At higher frequencies it uses an ADF4350, which has a rated output power in the -4 to + 5 dBm range.  By the time that get through the various switches, the bridge, and so on, I'd expect it will also be in the same range as the version 1s.  I measured my NanoVNA-H at - 9 dBm the other day.


hwalker
 

On Sat, Mar 28, 2020 at 10:49 PM, Joe Burkleo wrote:

One thing I have not seen in the spec's so far is what the output level is.
Have you measured that or do you know what it is?
If I remember correctly the original version was in the -10 dbm range.
==========================================================
Joe,
I haven't gotten around to measuring the output levels. I'm not sure how accurate my power meter is pass 1 GHz. If it helps these are the levels that Gabriel has annotated on her schematic.

IN to OUT transmission: −10dB
IN to REFL (OUT shorted): −30dB
IN to REFL (OUT open): −30dB
Coupling factor: −20dB

I not sure if the -10dB IN to OUT transmission is really dBm or actual loss through the directional coupler. Most directional couplers I've used have less than a dB through loss.

- Herb


mcebokli@...
 

Hello Herb,

you mention the schematic - can it be seen somewhere online?
I will definitely buy this, but I can not do it currently from Tindie, not shipping to Slovenia (in fact, there is a quite long list of "no ship" countries there). Hopefully, this will change - don't want to pay double at Ebay.
Also, currently the postal service here in Europe is out of whack because of COVID, I am waiting for some other parcels for quite long now, if they will arrive at all. I will wait a bit anyway, order later, if still alive.
So, in the mean time I would like to at least study the schematic :-)

Marko Cebokli


Dragan Milivojevic
 

Schematics at: https://gitlab.com/bepissneks/S-A-A
gEDA format.

On Mon, 30 Mar 2020 at 11:15, <mcebokli@...> wrote:

Hello Herb,

you mention the schematic - can it be seen somewhere online?
I will definitely buy this, but I can not do it currently from Tindie, not
shipping to Slovenia (in fact, there is a quite long list of "no ship"
countries there). Hopefully, this will change - don't want to pay double at
Ebay.
Also, currently the postal service here in Europe is out of whack because
of COVID, I am waiting for some other parcels for quite long now, if they
will arrive at all. I will wait a bit anyway, order later, if still alive.
So, in the mean time I would like to at least study the schematic :-)

Marko Cebokli




hwalker
 

you mention the schematic - can it be seen somewhere online?
=============================================
Marko,
The attached file is the version 2_2 schematic provided by Gabriel.

- Herb


mcebokli@...
 

Thank both of you very much! Great people on this list!

Marko Cebokli


John Gord
 

I don't remember this being mentioned before:

When the S-A-A-2 (NanoVNA-V2) frequency is changed, it does a "self cal" using an open, short, and load on its Port 0 input switch. The result is not great, but it is not terrible for some purposes. It seems to do a pretty good job near the center of the Smith chart, but not so well at the edges. Other than the expected phase differences due to the different calibration plane, it works quite well from 20 MHz to 700 MHz. I assume that the "raw" data it reports over the USB port actually uses this self-cal.
My unit has firmware version git-20200229-aea0dc4.

--John Gord


hwalker
 

johncharlesgord wrote:
I don't remember this being mentioned before:

... When the S-A-A-2 (NanoVNA-V2) frequency is changed, it does a "self cal" using an open, short, and load on its Port 0 input switch...

... I assume that the "raw" data it reports over the USB port actually uses this self-cal. My unit has firmware version git-20200229-aea0dc4....
==================================================================

John,
Gabriel never mentioned any "self cal" feature in the S-A-A-2 user manual. It just says the The S-A-A-2 is a single switched receiver VNA. Two channels are selectable by the receive mixer through SW_RECV, and a third channel, the reference channel, is provided by setting SW_ECAL to the “open circuit” position. By controlling these two switches the receiver is able to observe reference, reflected, and thru signals.

In message, https://groups.io/g/nanovna-users/message/12051 , Gabriel was asked a bout the USB data transfer and she replied.

"The USB interface always outputs raw, uncalibrated values, as is in the user manual. The reason is the assumption that the PC software always has superior calibration routines (e.g. supporting arbitrary cal kit parameters) and it is far less error prone if you can't be confused whether you are reading calibrated or uncalibrated values."

In my own testing if I change frequency parameters, calibration is turned off and no interpolation or correction is applied. Most of my testing is S21 and after changing frequency, without re-calibrating, the results are terrible. If "self cal" is applied for S11 measurements I don't see the benefit since as you said the measurement plane would be different. I could see such a feature being used as a self-test during manufacture.

My S-A-A-2 just arrived last week and has firmware version is git-20200117- 4c067eb. Your version git-20200229-aea0dc4 is newer but I'm not sure what the difference is. The latest release at https://github.com/nanovna/NanoVNA-V2-firmware/releases says that it is the "First production release" so I assume there is no advantage to me updating.

- Herb


OwO
 

There is no "self cal". There are corrections to track temperature drift, but this is not a full SOL calibration. The corrections are always happening and every sweep some small percentage of the time is allocated to it, except for the first sweep after changing frequency range which performs a full correction sweep, which is why the first sweep is much slower. If you compare the V2 to V1 you should see a big difference in temperature drift.