minivna - nonstop systems · – lots of other stuff • 1 to 180 mhz (possibly 1 mhz)1 to 180 mhz...

miniVNAminiVNA

Jim GerwitzAC7FNAC7FNJuly 2008

Rev I

What a miniVNA “is”What a miniVNA is

• VNA - Vector Network AnalyzerVNA Vector Network Analyzer• Useful for:

– FiltersFilters– Antennas– Cable lengthsCable lengths– Lots of other stuff

• 1 to 180 Mhz (possibly 1 Mhz)1 to 180 Mhz (possibly .1 Mhz)• Replaces MFJ-259/269 Antenna Analyzer

– (And others)– (And others)

What it looks likeWhat it looks like

Was reviewed in August 2008

InfoInfo

• Requires Computer for operationRequires Computer for operation• USB or RS-232 versions are available• Computer supplies power (USB only)• Computer supplies power (USB only)• Device has BNC two connections

DUT Device Under Test– DUT - Device Under Test– DET - Detector

• CAUTION: Be very careful during use• CAUTION: Be very careful during use. The unit is RF sensitive as are most analyzersanalyzers.

(Some of ) What it does(Some of ) What it does* Measures VSWR, RL, Rs, Z +/-jX, Phase, Cable length, R/L/C * F 1Mh t 180MH* Frequency coverage 1Mhz to 180MHz* DDS Signal Generator with 0 dbm output* 2 Ports allow Transmission Measurements e.g. filters, traps* Save and Load previous measurements p* Finds Minimum VSWR automatically* USB 1.1 and USB 2.0 compatible* RS232 optional socket, for Pocket PC`s or Remote Displays* Fast Scan (typical 0 6 sec for 500 points) Fast Scan (typical 0.6 sec for 500 points)* Use of an internal commercial Directional Coupler* High Reflection Dynamic Range 40dB to 35dB (VSWR 1.06:1 or better)* Wide Transmission Dynamic Range > 50-55dB* Transparent box with LED indicators for the operation status* In-Circuit-Programming for future firmware upgrades* Bluetooth compatible

The piecesThe pieces

• A computer (DOS Linux Windows)A computer, (DOS, Linux, Windows) • The miniVNA and cable to computer

Th S ft t it i iVNA• The Software to run it – miniVNAxxx.exe• OPTIONAL

– Zplots+ (requires Excel) • Not required but very beneficial (free)

– An iPAQ Pocket PC in place of the computer

General Screen Format

Screen Format Notes“Run” button

MODE selection buttonsFunctionsRun button –

Green with VNA attached

SWR as ReturnGraphicalChartingSWR as Return

Loss (db)

SWR scale

Charting area

Offset

Enable Mkr 1Left button

Enable Mkr 2

Data

Enable Mkr 2Right button

Sweep Range

f

Parameters for display

Preset Frequency ranges Number of stepsIn graphs –suggest 120

Multi-use area

Some Usage ExamplesSome Usage Examples• 80 M vertical screwdriver antenna• 40 M vertical screwdriver antenna• 80 – 10 M Windom antenna• Filter tuning• Tuning Stub• Crystal measurement• Cable length measurement• Signal Generator• Zplots+

80 M Screwdriver Antenna

80 M Ant Screen FormatAnalyzer Mode

VNA connectedAnd scanning

SW Version

Auto find minSWR enabledL b l bl dLabel enabled

AllParam’sdisplayed

End sweep

Start sweepStart sweep

“Q” Enabled for illustration only

80 M with Zoom

40 M Screwdriver Ant

80 – 10 Windom Ant

Testing Cable LengthConnect the unknown cable to the DUT connector, th li k th “Fi d A t ti ll ” b tt

Testing Cable Length

then click the “Find Automatically” button.

It will take some seconds until you see the correct ylength. The cable length is calculated from adjacent Phases at +90° and dependant from production tolerances of the Velocity Factortolerances of the Velocity Factor.

It is still possible to set the 2 Markers and measure ll D t t t ith Si l Smanually. Do not try to measure with a Single Sweep.

Cable Length Screen Format

Preset Velocity factorCalculated length

Testing Bandpass FiltersTesting Bandpass Filters

• Connect the filter between DUT andConnect the filter between DUT and DET. If it has an Insertion Loss you can compensate for it in the Losscan compensate for it in the Loss Offset box. (Suggest 3db attenuators)

• To view the 3/6/10dB Bandwidth just• To view the 3/6/10dB Bandwidth, just set both markers and enable the BW&QBW&Q.

28MHz Bandpass Filterp

IL ffIL offsetTo position graph

10 db BW

Tuning StubTuning Stub

Testing a 10 Mhz XtalTesting a 10 Mhz Xtal

• Connect the XTAL to the DUT• Connect the XTAL to the DUT connector and find at what f it h th l tfrequency it has the lowest impedance.

• You may need to Zoom the frequency range a couple of times.frequency range a couple of times. The Q and Bandwidth can be found where the Phase is 45°where the Phase is 45

10MHz XTAL

Signal GeneratorSignal Generator

Calibration Screen Set Frequency

S h?Seen enough?

W ll h ’tWell you haven’t seen Zplots!Zplots!

Zplots+ Screen Format

Earlier 40 M data

Smith Chart version

Links• miniRadio Solutions

– http://www.miniradiosolutions.com/• SW for Windows DOS Linux and miniVNA purchase SW is freeSW for Windows, DOS, Linux and miniVNA purchase. SW is free.• Schematics, P/L and manual• Link to Zplots+

• YahoogroupsminiVNA at:– miniVNA at:

• http://groups.yahoo.com/group/analyzer_iw3hev/

• COST $398.99 from W4RT at:– http://www.w4wb.com/Misc/miniVNA.htm

• An ‘Extender’ to 2.88 GHZ is in development

• And no, you can’t borrow mine.

Jim G AC7FNJim G AC7FN