vna1samplemeasurment

VNA1 sample measurment

Some measurment of VNA after calibrations

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

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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

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HARDRAWE CALIBRATIONS

Now i describe How I do this on my homebrewed VNA

if someone try this do - do this on it own risk :-) !!!!!!!!!!!!!!!!

>>>>>>>>>>>

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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

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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)

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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

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then repeat for check all steps...

73 !! Jarek SP3SWJ

http://sp3swj.googlepages.com/

aktualizacja 21 lipca 2007

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