Impedance Measurements David Conn VE3KL Ottawa Amateur Radio Club, Nov 2007 I have conducted a study to address the problem of noise in urban environments and will share my results with you tonight. I will give you two graphs that you can use at home to evaluate signals and noise using a simple S meter A method that you can use easily to evaluate your own noise environment A method that you can use to evaluate the quality of the ionosphere at any give time. Some methods to control received noise The Shannon Hartley limits 11/15/2018

Acknowledgments Greg Danylchenko VE3YTZ Henry Hall General Radio Bryan Campbell VE3ZRK Croft for sponsoring me for QCWA membership Gus for the invitation Doug for reviewing the presentation and providing the lap top for power point Ernie for taking measurements at his site to check my work. 11/15/2018

Introduction Basics….What is Impedance A Short History of Impedance measurements The General Radio 1650-A Bridge AIM4170 Vector Impedance Meter Telepost L-100 Vector Wattmeter Demonstrations 11/15/2018

What is Impedance Use A Dual Beam Oscilloscope Time Keep antenna far away from the house. Use good ground stakes Two noise types Graph from W5BIG 11/15/2018

Impedance Children SWR Cable Loss Cable Length Transformations Reflection Coefficient Magnitude and Phase Z Velocity Factor Return Loss Receiving Antenna described by its effective area Cable Zo Smith Chart Z: Impedance And Much More 11/15/2018

History Time Line Euler’s Theorem (Essential for Smith Chart) Ohm’s Law 1826 Christie Invents the Diamond Shaped Bridge Fourier & Gauss (Fast Fourier Transform) Wheatstone Bridge (same a Christie’s) Maxwell Transient Bridge Wien AC Bridge General Radio 1650-A AC Bridge Introduce a few terms such as effective area. Literature uses area and field strength as a pair: must know idea about effective area. Cooley Tuckey FFT Digital and PC era 1748 1826 1833 1855 1843 1865 1891 1959 1965 1970 11/15/2018

General Radio 1650-A Bridge Five Bridges in one instrument (R, L, C, Q, D) Manual point-by-point data collection Voltage and Current not measured Includes a novel OrthoNull Mechanical computing device Two logarithmic coupled dials First Bridge to use Transistors We need to use four terms 11/15/2018

Maxwell Bridge ..Type 1 Measures L and Q All Pass Network (DC or AC or Transient Operation) Two Variable Resistors Resistors Interact We need to use four terms 11/15/2018

The Aim 4170 Impedance Meter Measures load voltage and current Uses two DDS synthesizers as RF source Passes IF digital signals to PC PC performs FFT to compute magnitude and Phase of Z Many charts from 1 to 170 MHz produced We need to use four terms 11/15/2018

The Aim 4170 Impedance Meter Lindenblad 2 Metre Antenna We need to use four terms 11/15/2018

Telepost LP-100 Digital Vector Wattmeter Measures RF load voltage and current through a coupler Most calculations done with a PIC microcontroller Measures and displays power up to 3000 W Measures Magnitude/Phase electronically…. No FFT Many charts from 1 to 170 MHz produced We need to use four terms Coupler Main Unit 11/15/2018

Telepost LP-100 Digital Vector Wattmeter We need to use four terms Polar Plot Mode Impedance Mode Reprinted with Permission from Telepost 11/15/2018

Summary Older Bridges collect data one point at a time New Instruments measure voltage and current Aim4170 Measures Impedance Telepost LP-100 is a multi-purpose Digital Vector Wattmeter 11/15/2018

73 David 11/15/2018