World Headquarters, Beaverton, Oregon, USA
Our business Design and Manufacture of RF coverage measurement and mapping instrumentation Emphasis on digital and analog television coverage measurement Specific expertise in automated RF measurement and analysis of DTV quality of service
Our television customers Transitioning to 8VSB digital service Operating analog and digital plants
• • • • •
New transmission formats New power levels New channel assignments New antenna locations New government regulations
Cost and people constrained
Antenna Patterns
Not always as you would expect
6.5 miles from 1000’ AAT
Horizontal Gain Oded Bendov / Krishna Praba, Television Engineering Handbook, Jerry Whitaker
Vertical Angle Gain
Z Technology measurement systems
Address specific measurement needs • • • • •
documentation identification acceptance confirmation resolution
DSS5800 DTV measurement system
DSS5800 DTV measurement system
Programmable field strength meter
8VSB data demodulator
GPS Receiver
Power and Distribution
Laptop Windowstm PC AC
DC
DSS5800 DTV measurement system
Programmable field strength meter
8VSB data demodulator
GPS Receiver
Power and Distribution
Laptop Windowstm PC AC
DC
DSS5800 DTV measurement system
Programmable field strength meter
8VSB data demodulator
GPS Receiver
Power and Distribution
Laptop Windowstm PC AC
DC
DSS5800 DTV measurement system
Programmable field strength meter
8VSB data demodulator
GPS Receiver
Power and Distribution
Laptop Windowstm PC AC
DC
Three measurement techniques 1. Drive testing • rapid accumulation of data • identification of problem coverage areas
2. Calibrated testing • used to validate more general data • communicates very specific values
3. On-site testing • detailed evaluation of local conditions
Drive Testing
Rapid accumulation of coverage data • Calibrated measurement equipment • 7 ft. antenna height, on roads • Automatic capture and recording
Identification of problem areas • Relative to previous runs • Poor signal coverage • Changes in coverage
Drive Test Considerations
Equipment configuration • Antenna, Power, Mounting, Calibration • Convenience and Safety
Environment • Location, Obstructions, Reflections
Operator interface • Driver Distraction, Information Displays • Setup & Automatic Collection of Data
Mobile Test Antennas
Horizontal dipole • General direction towards transmitter • Magnet mount, ~24” above roof surface • Calibrated; antenna factors for dBuV/m
Vertical sampling antenna • Mag mount 1/4 wave vertical antenna • Not true to horizontal component • Characterized
Mobile Test Antennas
Omnidirectional antennas • Generally lower gain, uncalibrated • Subject to multipath distortions
Rotators • Dipoles are broad pattern • Just need a general direction • Beware of distracting driver
Antenna Correction Factors
Measured correction factors supplied by antenna manufacturer Add antenna factor plus cable loss to receiver reading in dBuV to convert to field intensity in dBuV/Meter. Example: • • • •
Antenna Correction Factor Cable loss Meter Reading Field Intensity
16.0 dB/m .9 dB 44.0 dBuV 60.9 dBuV/meter
Calibrate Antenna Setup
Mount antenna and adjust element length for frequency as indicated in manufacturer’s table Connect to measurement equipment with calibrated cable Add antenna correction factor for operating frequency and calibrated losses Enter system correction factor into meter or PC application software Meter or application will read field intensity in dBuV/m
Multiple Frequency Testing
Same band, one antenna • Factory antenna factors • Element length vs. frequency vs. factor • Characterizing for multiple frequencies
Multiple Antennas • Power combiners • Filters • System characterization
Multiple Antennas VHF UHF
LP Filter HP Filter
Power Combiner
dBuV/m
VHF ant correction factor - cable loss - LPF loss - Combiner loss - cable loss = VHF Antenna Factor (sys) UHF ant correction factor - cable loss - HPF loss - Combiner loss - cable loss = UHF Antenna Factor (sys)
Add antenna factor plus cable loss to receiver reading in dBuV to convert to field intensity in dBuV/Meter.
Calibration Procedures
Equipment certification • NIST traceable antennas, cables, field strength meter • Secondary reference
Equipment setup • 30 ft. antenna height vs. vehicle rooftop • Antenna factors recorded with data
Drive Test Procedure
Set up job • Frequencies • Antenna factors • Signal types
Adjust antenna direction • Spectrum display • Sample measurement
Start Drive Test • Hit record • Drive the route
DVB-T Spectrum & data display
8VSB Spectrum & data display
Signal Level (voltage) At Cursor Position (frequency)
8.8 dB 0.33 MHz (freq)
20 Log(.38)=8.4 dB Main Tap normalized To 100%
3 uS (time)
38% of Main Tap Energy (voltage)
Example Case: One major reflection at 3 uS causes a .33 Mhz ripple on the Spectrum Display
Percent Reflection (Voltage) At Cursor position (Delay)
Operational Precautions
Do not operate while driving Be aware of antenna orientation Stop and enter comments where appropriate Analyze recorded data later
The Drive Test
Set up the “job” for signal types and frequencies Click F1 “Sample” to check the reception Click F3 “Record Continuous” Drive until direction changes more than ~30 degrees; stop and adjust antenna direction Click F4 “Stop Measurements” Take a break and look at the data
Automatic data recording
Analog: records all setups, time, location, direction of travel, peak power, antenna factors, frequencies, etc. Digital: adds wideband parameters; integrated power, etc. DTV systems add data from the digital decoder; sync/eq locks, tap values, etc. Clear text data files are easy to read and export to other applications
Clear-text Data File
Analyzing the data
Real-time map plotting • Colored trail of dots for any parameter • Plots value as a color for each GPS location measured • Color may be automatically or manually scaled
Analyzing the data
Map oriented data • Colored trail of dots for any parameter • Tool-tip displays selected value for selected location • Right-click for all data taken at that location
DVB-T data parameters
8VSB data parameters
On-Site Testing
Problem resolution Difficult locations Sniff out problems Using customer antennas Site suitability
RF signal measurement products
Systems designed to meet specific industry needs • digital and analog RF field strength measurements • automatic signal coverage mapping • 8VSB/DVB-T demodulated data analysis
Our mission
Address the RF measurement needs of our customers Provide economical, real-time assistance and solutions Increase the confidence level of the technical operator Enable the gathering of historical data for reference as conditions change
Learn more about our systems Z Technology, Inc. 1815 NW 169th Place, Suite 3070 Beaverton, Oregon 97006 USA Tel: 503.614.9800 Fax: 503.614.9898 www.ztechnology.com
[email protected] Factory Contacts: Guy Lewis, John Purdy, Jim Zook
