HF Arduino Vna (english version)

DSC02691

By F4GOH

The main characteristics of Vna analyzer are:

  • HF : 1 MHz à 60MHz
  • Reflection and transmission analysis
  • Uses the DL2SBA Jvna software
  • Mode « Standalone »
  • LCD display 4 × 20
  • Bluetooth with Blue VNA Androïd software
  • Scrolling menu by rotary encoder
  • Cost € 50 without Bluetooth Module

The VNA is based on the following components:

  • Arduino NANO
  • Module ad9851
  • ad8302

ebay-links : components list

Pcb available mail me :  f4goh@orange.fr
Introduction :

This HF VNA is an adaptation of the scheme described in the Russian site RA4NAL. I use an Arduino Nano and system measurement on the same board. I add rotary encoder and lcd display to use the VNA in standalone mode. The PC software is Jvna same as miniVna from  DL2SBA.


you can use the VNA from 3 differents software interfaces:

Mode 1: Connect to PC

The VNA is connected to Arduino nano via miniUSB. The PC software is Jvna same as miniVna from DL2SBA (http://vnaj.dl2sba.com).
It is possible to analyse antennas in reflection mode or filter in transmission mode.

08 vna refl

Mode 2: Connect via Bluetooth Module

The VNA is connected to via Bluetooth Module. Using blue VNA software, it is possible to analyze antenna like on PC computer, except you can up the VNA on the top of your pylon.
you can then perform analysis without cable.
(https://play.google.com/store/apps/details?id=ro.yo3ggx.btvna&hl=fr)

09 android

Using Mode 3 in « Standalone ». Just a 5V power supply to operate all. With mSd Card inserted, all measurements is saved in a text file. It can be possible to anayse them on a spreadsheet.

DSC01370

The information of antenna parameters are displayed on a 4 x 20 character LCD screen. The selection of the band or frequency is done with a rotary encoder.
the handling is quick and has few menus.


Main board description :

02 minivna_hf
V2 schematics

We can easily recognize the RA4NAL scheme, the Arduino UNO was replaced by a NANO facilitating the integration of the USB connection.

The AD9851 DDS is an oscillator, the signal is amplified by an ERA2SM and attenuated by R25,R26,R27 before attacking the tandem coupler based on a BN43-202.

The direct and reflected power of the coupler is attenuated by a couple of T Résistors and  injected into a ad8302
The ad8302 will give us a DC voltage proportional to the magnitude and phase of the two signals.

These two voltages Vmag Vphs and are converted into an average of 20 digital values by the Arduino.

In PC software mode , these numericals values is directly transferred into Jvna software. Jvna compute all antenna parameters like RL, |Z|, |XS|, theta, swr.

SPI connection is shared between the DDS and the MSD card. Knowing that the power supply of the MSD card is 3.3V, it will add tension divider to Arduino.

The LCD display 24 × 20 characters is controlled via the I2C bus provided that it is equipped with a PCF8574 interface (I2C Serial Interface Module For LCD1602 Display).

Beware to use an bluetooth module (connected on J7) is compatible 5V level I / O, because this is not the case for all modules.

If you wish to scan with Jvna software on PC, you must disconnect the Bluetooth module in order not to provoke conflict on the serial line.

The LED D3 lights when there is a data transfert on the serial line.

Omron relay allows to activate the mode of transmission and thus measure the gain of a filter interposed between the DUT output and input DET.

10 vna transIf you want to use mSD card, you must load VnaArduinoSd.ino into Arduinonano, and install Arduino sdfat library. Insert your mSDcard into a module and connect it to J3.


Soldering and testing:

Start with soldering the support of the Arduino Nano, support for the AD9851 DDS, the connector of the LCD display and rotary encoder. (rotary.png)

Do not forget the decoupling capacitors and anti-bounce. (C12, C18, C20, C21)

rotary

VnArduino.ino program the file in Arduino from the following link:

https://github.com/f4goh/VnArduino

Use xloader if you want to upload firmware without compilation

upload

Hold the rotary encoder button for switching on to access the menu.

04 compil menu

From the menu, choose JVNA

Once validated, then the Arduino reset itself into JVna mode

Start Jvna on your computer, choose the correct COM port in the « driver selection » menu and « miniVNA ». Make a connection test and click update.

05 connexion jvna

Perform a phony reflection calibration for now, then in the frequency calibration menu adjust the DDS ticks 23,860,477 to be compatible with the AD9851.

06 calibration dds

Go into the GENERATOR menu, click « on air », then check the frequency generated with an oscilloscope on the DDS output. (10Mhz) Adjust ticks to obtain 10Mhz with a frequency counter.

07 bis generator

Solder now the ERA-2SM amplifier or an equivalent component of your stock.

Recheck the output signal of the amplifier with an oscilloscope

dds pa out

Now weld the measuring bridge (tandem coupler) and the T attenuators.

The tandem coupler used to measure the direct and reflected powers is made with a binocular toroid BN-43-202 (2×5 turns, 0.5MM)

tandem

03 tandem

On 50 ohm load, check with an oscilloscope the voltages across R12 (max forward voltage) and the terminals of R6 (reflected voltage near zero).

Without load (open output), with an oscilloscope check the voltages across R12 (max forward voltage) and the terminals of R6 (max reflected voltage).

Finish by weld the components around the ad8302.

Check with a voltmeter the reference voltage VREF supplied by ad8302 to be 1.8V.

The VNA is ready for use.

Repeat calibration, this should match the screenshot below.

07 calibration data To use the « standalone » mode, it will be necessary to perform a calibration (menu on the 4th line of the LCD display).

The location of calib resistors are used to adjust the load on measurement for 50ohms RS = 50 ohm.

It is then necessary to place a single resistor with a value between 300ohms and 2Kohms on one of the two sites, but perhaps only will you not need.

73 and good parts assembly


Improvement of the measurement by F1AIA:

Below the diagrams containing the changes to be applied at the level of attenuation values as well as the amplification part with the replacement of a ERA to SGA3386. By applying these corrections, you can be measured attenuations to -40dB and S11 values or Return Loss (RL) -35 to-39dB.
The dynamics of the whole is enhanced with better amplification of SGA, accompanied by a better choice of reference values applied to the inputs of the AD8302.

Jean-Claude thank you for this info.

schema-att-modifie

modif_era
SGA3386 with his 68 ohms resistor
p1080221
DET attenuation correction
minivna_hfv3
V3 schematics

minivna_hf-copper_v3


OZ6HR Edition

oz6hr edition

minivna_hfV12

pcbV12_1

pcbV12_2

  • Choose U2 or U4 depend of ad9851 pad(if you use U2 put a strap on J10 (2-3)
  • For card reader  choose J3 or J9 depend of sd reader (if you use J9 do not put R16 to R21and R10 resistors)

sd card

Update file on github for special OZ6HR edition


Congratulation Rainer (OE1KFR)

rainer

Thanks to YL2GVC for his picture, great !

VNArduino YL2GVC

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20170819_110241
Luca I6QIZ
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Luca I6QIZ
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Ray m0dhp
Publicités
HF Arduino Vna (english version)

28 réflexions sur “HF Arduino Vna (english version)

  1. Preben Larsen dit :

    Hello Anthony
    I am going to put a VNArduino together, but wonder if the change in attenuation values,
    only is to be done together with the SGA mmic amp, or could be done in all situations?

    Aimé par 1 personne

  2. Armin dit :

    I’m about to start building this project, but I’m not sure about how to find the values for calibration resistors R11 and R22. Any tips?

    73 de DJ2AG

    J'aime

    1. The location of calib resistors are used to adjust the load on measurement for 50ohms RS = 50 ohm.

      It is then necessary to place a single resistor with a value between 300ohms and 2Kohms on one of the two sites, begin with 2kohms on R11 or R22 and see what happens. change value and placement if necessary. Personally i weld nothing.
      73

      J'aime

  3. Armin dit :

    Hi Anthony,

    would it be possible to get hires (V3) schematics (github)? I like to have a printed schematic at hand during assembly, but with the low res pictures on the website, R and C values are almost unreadable. Would be a great help.

    73 de Armin
    DJ1AG

    J'aime

  4. Claudio dit :

    Hello,
    PCB received, very well designed, well made, Thanks again, Anthony!

    Last night I have completed the assembling, following the schematic with 20dB and 2dB attenuators + 8dB attenuator on the DUT port; I have double… triple-checked everything and tonight I will start the first tests.

    Now I have two questions:
    1. I don’t have SGA3386, so I have used the ERA-2SM; however, I have changed the R32 (20 Ohm, in the original schematic), because the ERA-2SM bias parameters are Vs= 3.4V and I=40mA (from datasheet), so the R32 result (5 – 3.4)/0.04 = 40 Ohm; it’s right or any suggestions?

    2. Using the mods suggested above the attenuators ( 20, 2 and 8 dB), how the Arduino firmware knows that? Will be necessary to recompile the FW, starting from the VNArduino-master, after adding something to the code?

    Thanks,
    73, Claudio

    J'aime

    1. hello,
      yes , ok to use 40 ohms for ERA-2SM 20ohms is too low
      you don’t need to recompile the FW.
      if you take a look at ad8302, to see that mag is a ratio MAG = log(Vina/Vinb)
      so if you add attenuators the ratio is the same.
      the other output is the phase, no problem.
      73
      Anthony

      J'aime

  5. Claudio dit :

    Hello,
    I have done the first test, in reflection and transmission mode.
    Just two simple test, of course after the calibrations:
    in Reflection mode with e dummy load, with results as expected (SWR very near to 1, Rs very near to 50 Ohm and Xs near 0 Ohm).
    In Transmission mode with a -30dBm attenuator from DUT to DET, again with results as expected (TL near to -30dB).
    I’m sure that it will be a very useful tool for my lab!
    73, Claudio

    J'aime

  6. Ray dit :

    Hello Anthony. Are the two calibration resistors only required to operate in standalone mode, and they are not required if using the VnArduino with vna/J?

    73 Ray

    J'aime

  7. if I select standalone and select band and press button I’m back in select band menu. The programm not stops on R,Xc…Every time I select band *XXm and button I can not see value. I can see X,R for few mseconds and back again in select band….any advice how to stops in vaules? or I missed something?

    J'aime

    1. try vnarduinosdcardV2 eng without sd card.hex
      be sure that lcd i2c driver was 0x27
      LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); //4 lines *20 columns lcd char
      if not change to 0x3f

      J'aime

  8. Paul Hughes dit :

    Excellent project, there’s a lot of good work your arduino software.
    Ive been looking at designs using IQ to measure mag and phase but conclude the AD8302 will give adequate results for my ham use.
    One thing I do not understand. The AD8302 cant distinguish phase between 0 to +180 deg and 0 to -180 deg. ie same voltage is output for +ve or -ve phase. How is this solved in the measurement calculations?
    Also

    J'aime

  9. Claudio dit :

    Hello,
    agreeing to use a bluetooth module with 5 Volt level in/out compatibility, which module type I need to choose? Master-Slave (HC-05) or Slave (HC-06)?
    Thank You,
    Claudio

    J'aime

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