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
© SP3SWJ
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