1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. Man-Made Noise Analysis
Data from ITU-R P 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

19. 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

20. 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

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

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

23. 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

24. 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

25. 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

26. 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
1/18/2019
David Conn VE3KL

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