Signals and Noise in Amateur Radio Systems David Conn VE3KL 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 1.38*(10-23) 1/18/2019 David Conn VE3KL

Acknowledgments Croft Taylor VE3CT Gus Holtz VE3VK Doug Leach VE3XK Ernie Bartels VE3GNU 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. 1/18/2019 David Conn VE3KL

Introduction A talk about signal to noise ratios in amateur radio systems: SSB, CW, PSK31 You will learn how to estimate the effective area or your antenna You will learn how to evaluate man-made noise with an S meter 1/18/2019 David Conn VE3KL

The Radio System Antenna Balun Ground Signal + Noise Power line Noise Coiled coax Keep antenna far away from the house. Use good ground stakes Two noise types Tx/Rx Ground 1/18/2019 David Conn VE3KL

סּ ├ The Radio Model Rx Tx Ionosphere Г Isotropic Short Dipole R Loss Doppler: limits PSK31 Amplitude distortion Isotropic Short Dipole סּ ├ Receiving Antenna described by its effective area Rx Tx R Power = 1.0 W Transmitted Power, Noise S/N S Meter Bandwidth 1/18/2019 David Conn VE3KL

Agenda The S meter The Shannon Hartley data limit Effective Area of a receiving antenna Free Space Power Calculations Noise types and man-made noise Noise in quiet rural, rural and residential areas Solutions Summary Introduce a few terms such as effective area. Literature uses area and field strength as a pair: must know idea about effective area. 1/18/2019 David Conn VE3KL

Definition of Terms P, N rms power [Watts] S is the reading on an S meter. Aeff is the effective area of a lossless antenna, related to directivity Field strength (Volts/m) is a measure of the electric field strength at the receiver We need to use four terms 1/18/2019 David Conn VE3KL

The S Meter Our Basic Power Meter Measures Power at the receiver input Usually not well calibrated We use the S meter for all of our measurements S 9 refers to -73 dBm at the receiver input 50 uv A noise level of S6 is tolerable if the signal is S9 1/18/2019 David Conn VE3KL

The Shannon Hartley Limit CW Morse Code: P/N = 3 S units, B= 100Hz Then: C = 1438 words per minute P is the signal power N is the noise power B is the receiver bandwidth Shannon Hartley gives us a goal. We have a long way to go P = S9 N =S6 B=100Hz 1/18/2019 David Conn VE3KL

The Shannon Hartley Limit CW Morse Code: P/N = 3 S units IF C = 20 words per minute Then: B = 1.4 Hz Hence we have along way to go 1/18/2019 David Conn VE3KL

Effective Area As we see later the effective area of a satellite dish is closely related to its physical area 1/18/2019 David Conn VE3KL

Effective Area of a Short Dipole Area not a function of dipole length For a 20 m dipole Aeff = 48 square metres Area depends only on λ2 Short dipole has and area much less than the square of the wavelength 1/18/2019 David Conn VE3KL

Effective Area: Parabolic Dish A 2 metre parabolic dish Freq = 1296 MHz Wavelength = 23.8 cm Physical area = 3.14 square metres Aeff = 1.73 square metres Here is an example of a parabolic dish with 55% efficiency 1/18/2019 David Conn VE3KL

A three element 10 m Yagi, free space Effective Area: Yagi A three element 10 m Yagi, free space Gain = 8.4 dB Aeff = 55 square Metres A three element 10 m yagi 1/18/2019 David Conn VE3KL

Agenda The problem: signals, ionosphere, noise The S meter The Shannon Hartley data limit Effective Area of a receiving antenna Free Space Power Calculations Noise types and man-made noise Noise in quiet rural, rural and residential areas Summary I use free space calculations as a reference 1/18/2019 David Conn VE3KL

Received Signal Power Power Transmitted = 1.0 W Here a 10 square meter antenna will produce S4.5 over as path from Ottawa to Vancouver 1/18/2019 David Conn VE3KL

Agenda The problem: signals, ionosphere, noise The S meter The Shannon Hartley data limit Effective Area of a receiving antenna Free Space Power Calculations Noise types and man-made noise Noise in quiet rural, rural and residential areas Solutions Summary 1/18/2019 David Conn VE3KL

Man-Made Noise Analysis Data from ITU-R P.372-7 Report Man-made noise relative to thermal noise. Not dependent on the bandwidth Thermal, shot and 1/f noise Translate to S units for our use. Data from the ITU Noise relative to thermal in units of field strength at the rx 1/f noise like an earth quake in the silicon chip. 1/18/2019 David Conn VE3KL

ITU Noise Data (Field Strength) Notice that Residential area have about 100 times the noise of quite rural 1 W transmitter compares to 100 Watts! 1/18/2019 David Conn VE3KL

Noise in SSB BW = 2700 Hz Noise measurement translated to S units This is a hand out that you can use at home to check your environment compared to the ITU data Note that the 40 m band will produce S5.5 in residential areas 1/18/2019 David Conn VE3KL

Noise In CW BW = 500 Hz CW is better: less than S5 1/18/2019 David Conn VE3KL

Noise in PSK31 BW = 62.5 Hz PSK is better: S3 1/18/2019 David Conn VE3KL

Keep antennas away from houses and power lines. Solutions Keep antennas away from houses and power lines. Use a Balun at the antenna Use shielded coax cables for best results. Use a grounding system to suppress noise that comes from currents flowing up to the antenna on the outside of the coax. Bury the coax cable: moisture problem? 1/18/2019 David Conn VE3KL

Filter external cable noise with a PI network Signal + Noise Antenna Balun Power line Noise Coiled coax Keep antenna far away from the house. Use good ground stakes Two noise types Tx/Rx Ground 1/18/2019 David Conn VE3KL

Summary Main output: S meter graphs for SSB You can use these graphs to evaluate your own location We have a long way to go to get close to the Shannon - Hartley limit The issue of noise pollution needs our attention and careful measurements 1/18/2019 David Conn VE3KL

Where to Get More Information RAC Web site: look there first ARRL Web site Details in my web site as it develops Fields and Waves in Communication Electronics: Ramo, Whinnery, Van Duzer ; John Wiley, third edition, 1994, ISBN 0-0471-58551-3 1/18/2019 David Conn VE3KL

Thanks for attending 73 David 1/18/2019 David Conn VE3KL