Measurment performed using two software:

- VNA V 3.0.2   http://sp3swj.googlepages.com/VNA_302.exe

- Zplot  http://ac6la.com/zplots.html

 

 

( link with  software for VNA)

 

 

Measured made after Calibrations. (Procedure described in end of the page )

 

 

 

ZERO ohm terminaotr 

 

 

 

 

 5o OHM terminator  (number 1)

 

 

 

 

 5o OHM terminator  (number 2)

 

 

 

  10o OHM terminator

 

 

 

 

 

 

 20o OHM terminator

 

 

 

Cable RG58 measurment 

 

 

 

 

 

Xtal - in Filter mode 

 

 

 

 

 

 RG58 terminated in 82 ohm on the end

 

 

 

 

Calibrations Procedure 

 

 

Full Calibration - this is SOFTWARE and HARDWARE calibrations !!

this is for this ver. SW V 3.0.2 dla USB/RS232
http://sp3swj.googlepages.com/VNA_302.exe
( set the correct INI valuse - dds clock  etc)

You can use Zplot program too for this actions

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You should prepare
- SHORT terminator - just BNC connector with pin connected to ground

- 50 ohm terminator - made from two 100 om 1% SMD resistor
!!!!! not use LAN terminator described as 50 ohm this is 51 ohm !!!

- 200 ohm - made from two 100 om 1% or other precise resistors

- short coax cable to connect IN and OUT

usefoul will be for additional test
- Xtal - for Filter mode test measurment
- trimmed resistor 330 ohm - used as termonator
(BNC connector with potentiometr)

in VNA version 30 dB  -n both input You shuld have  51 ohm 

 

During calibration You connect parallet  4,7 kom potentiomet  to this 51 on proper input (read below)

 

 

in VNA version 40 dB  - place to connect trimmed resistor is  little different

 

 

 

 

 

"FIGHT  WITH WIRE"

 

if our VNA works fine - we need little correct WIRE  on  Coupler

 

just connect  50 ohm terminator ( not  51 !!!!)

 

and  correct  WIRE  for  minimum  RL  and  posibble flat  PHASE

 

 

 

 

 

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

 

 

 

 

 

SOFTWARE CALIBRATIONS

 

1.1  DDS Clock error  

 

( not  needed normally becose normally errors  is   maybe  hundret Hz    - not important for antenna)

 

When DDS Xtal generator heat some time - You can correct reference oscillator in INI file
- do this only if You need use as GENERATOR FUNCTION and You have calibrated frequency meter

do this for maximum high frequency  for example 50 Mhz...

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1.2 made in VNA mode

>> connect SHORT terminator on VNA port
>> set RL_OFFSET_vna=0 in INI file
>> scan all range
>> switch on RL chart
>> read value of RL value for most difference than ZERO-RL write this in INI
( or for some favorite frequency ~~~ for example 15 MHz)
>> restart SW

new value be about + - few dB

as separator use DOT !!!!!!!!!!! not commas

 

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1.3 made in FILTER mode
>> Connect port OUT >> IN with short coax cable
>> set RL_OFFSET_filter=0 in INI file
>> read value of RL value for most difference than ZERO-RL write this in INI
( or for some favorite frequency ~~~ for example 15 MHz)
>> restart SW

new value will be about 15 dB



========

HARDRAWE CALIBRATIONS

Now i describe How I do this on my homebrewed VNA
if someone try this do - do this on it own risk :-) !!!!!!!!!!!!!!!!

>>>>>>>>>>>
------------------------------
For my homebrewed VNA I perform two hardware calibrations

- connect 50 ohm terminator and calibrate for PHASE ~~~~>>  90 degree

- connect 200 ohm terminator and calibrate for Z-imp ~~~~ >>200 ohm

------------------------------
2 PHASE CALIBRATION -
- connect 50 ohm reference -terminator
- measure PHASE
- adjust potentiometron input PHASE on IC AD8302 for readout 90 degree
- solder correct resistor
- in example I solder 51 ohm and trimmed 4,7 kom.... then for finish

For example i my VNA  finnaly I have two fixed resistor eg 51 and 1800 ohm in parallel

(Remember - measurment line never is flat)

 

-------------------
3 Z-imp calibration

 

 

Bwfore perform steps  below  -  try to  little correct RL_ VNA_OFFSET    

for   200 ohm readout for 200 ohm terminator measurment

 

if differences  is to big...   perform   steps  below

 

- connect 200ohm reference -terminator
- measure Z
- adjust resistor on input MAGNITUDE on IC AD8302 for readout 200 ohm
- solder correct resistor
- in example I solder 51 ohm and trimmed 4,7 kom.... then for finish

For example i ny VNA  finnaly I have two fixed resistor eg 51 and 900 ohm in parallel

this Zimp curve will not be flat !!!!!  in this pocedure - this is normal !!!

 

(Remember - measurment line never is flat)

 

 

when is some problem tune  to 200 ohm  ...   change  51  >>  56  ohm  and  repeat  procedure

 

====================
then repeat for check all steps...

73 !! Jarek SP3SWJ