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VIA Bravo Network Analyzer

VIA Bravo Network Analyzer. What’s in this presentation?. What you gain by using a Network Analyzer Learn the difference between a Network Analyzer and Scalar Look at the dynamics involved with antenna performance aka “Smith Chart Intro” Familiarization with the VIA Bravo’s display

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VIA Bravo Network Analyzer

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  1. VIA Bravo Network Analyzer

  2. What’s in this presentation? • What you gain by using a Network Analyzer • Learn the difference between a Network Analyzer and Scalar • Look at the dynamics involved with antenna performance aka “Smith Chart Intro” • Familiarization with the VIA Bravo’s display • Preview Bravo PC VisionTM software • Summarization Plus Question and Answer session

  3. Why Use a Vector Impedance Analyzer? • Scalars provide SWR & Return Loss information, but not Vector Impedance. A high SWR reading doesn’t tell you what to fix or what to tune in an antenna system • The VIA Bravo’s information can be used to: • Maximize an antenna system’s efficiency • Document an installation with electronic or paper media • Diagnose an Antenna System to effect timely repairs • The VIA Bravo can be used at the antenna base or at the feed line using the “Nulling Cable” feature

  4. Optimize Your Antenna System to Enhance Range and Quality Tuned Antenna Un-Tuned Antenna Effective Radiated Power (ERP) Minimum Service Threshold Range

  5. Un-Tuned Transmission Tuned Transmission EXAMPLE of a COMMUNICATIONS IMPROVEMENT Proper tuning delivers more power and a higher quality of transmission from the same equipment and antenna system

  6. Reflection Coefficient Impedance Angle Impedance Reactance Resonance Capacitance Resistance Inductance Frequency What Chokes an Antenna? All the factors for antenna performance MUST balance or the result is Power Loss from out-of-phase current and voltage and increased VSWR from impedance mismatches

  7. Vector Impedance and the Right Hand Plane (RHP) X = Reactance, Z = Total Impedance, R = Resistance, θ = Z Angle, and i or j = square root of -1 Above, the positive X values plot into one quadrant of a Cartesian graph’s RHP, negative X values plot in the other quadrant directly below this one

  8. Inductive High Z Resistive Low Z Capacitive Mapping the RHP to a unit circle – Smith Chart Note where Zo plots – Dead Center is Antenna System Perfection

  9. ELI the ICE Man • For best performance an antenna should be purely resistive and resonant near Zo at the center frequency (Fc) • Power loss factors include: • If the antenna is inductive, voltage will lead current (ELI) • If the antenna is capacitive, current will lead voltage (ICE) • Either of these conditions exceeding the manufacturer’s specifications require corrective action by tuning the antenna or adding a tuning stub

  10. VIA Bravo Vector Impedance Analyzer Measures the impedance and resonant frequencies of antennas, coils, circuits & components 100 kHz – 200 MHz Single & Two Port Versions Bravo PC Vision Software

  11. VIA Bravo LCD Display Left = Unit of measure for selected test on Left vertical axis Right = Unit of measure for selected test on Right vertical axis FL>FC>FH = Frequency sweep range FL = Lowest frequency of the sweep FC = Center frequency of the sweep FH = Highest frequency of the sweep

  12. L = Numeric readout for Left Plot ( ) center frequency. In EXAM/PLOT the measurement at the cursor frequency R = Numeric readout for Right Plot (+++++) center frequency measurement or in EXAM/PLOT the measurement at the cursor frequency L/C = Numeric display of the inductive or capacitive component of the measurement. For SWR mode, L/C = the calculated “Q”

  13. Center Frequency An antenna is resonant at the frequency(s) where the Impedance (Phase) Angle is equal to zero (0). Left plot (thin) = Z of 50.6Ώ at resonance Right plot (thick) = ө Angle of 2.38o Smith Chart Positive ө Angle = inductive X at 19.7 nH. [Note: Negative ө Angle would = capacitive X]

  14. Frequency Sweep vs CW Mode Frequency Sweep Normal Mode One sweep about every second from FL to FH Tuning requires a 1-2 seconds wait for change to post Continuous Wave Mode Update rate is increased to about 5 times per second CW operates at Center Frequency – no sweep Tuning changes appear almost instantly Tuning by the numbers is faster No additional power drain on the batteries

  15. VIA Bravo II • Two ports (S11 and S21) add measurement versatility: • Antenna-to-Antenna Isolation • Amplifier Gain • Group Delay • Gain Compression • Differential Amplifiers • AM to PM Distortion

  16. VIA Bravo & PC Software Impedance Impedance Angle Resistance Reactance Smith Chart* VSWR Return Loss Reflection Coefficient • Magnitude • Angle • Capacitance • Parallel • Series • Plot save capabilities *In the Bravo PC Vision software which is included

  17. Bravo PC Vision

  18. Smith Chart from Antenna Sweep As the frequency changes the antenna’s reactance moves from inductive to capacitive with some impedance change and is resonant slightly off the center of the swept frequency

  19. Bravo PC Vision Software Upload Current or Stored Plots from the VIA Bravo Chart 8 Parameters at once Save Charts on a PC or on CDs Export Charts – (BMP, JPEG, GIF or TIFF) Produce Smith Charts Print Charts Create a Records data base and provide documentation to customers

  20. Weigh the Cost Against the Gain • Radio equipment - $$$$ • Antenna site or tower - $$$$ • Transmission lines - $$$ • Installation and turn-up - $$$ • Antenna Test & Tune - $

  21. VIA Bravo Bonus It’s not just for measuring antennae Tune ½ and ¼ wave transmission lines Measuring inductors and capacitors Tuning antenna traps Determine resonant frequencies Tuning cavity filters Adjusting antenna tuners Signal tracing Determine Cable Characteristics Use as a Signal Source

  22. VIA Bravo II Bonus It’s not just for measuring antennae Measuring Group Delay Measuring Gain Compression Measuring Differential Amplifiers Measuring AmplifierGain Measuring AM to PM distortion

  23. Summary • Proper antenna tuning for clear long range communications • Scalars provide only SWR and Return Loss, but NOT resonance information. Proper antenna tuning or diagnostic work requires a network analyzer • The VIA Bravo is a 100KHz to 200MHz network analyzer for antennas, coils, circuits or components • The VIA Bravo displays any two parameters at once, but stores all eight parameters measured • Bravo PC Vision will display all eight parameters at once

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