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

6. What Chokes an Antenna? Resistance Inductance Capacitance Impedance
Reactance
Frequency
Resonance
Impedance Angle
Reflection Coefficient
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. the Right Hand Plane (RHP)
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. Mapping the RHP to a unit circle
– Smith Chart
Inductive
Resistive
Low Z
High Z
Capacitive
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. 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]
Center Frequency

14. Frequency Sweep vs CW Mode
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 Tune ½ and ¼ wave transmission lines
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 Measuring Group Delay Measuring Gain Compression
It’s not just for measuring antennae
Measuring Group Delay
Measuring Gain Compression
Measuring Differential Amplifiers
Measuring Amplifier Gain
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