1. Noise in Amateur Radio Receiving 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
Credit: Nasa and Jack Newton
K = 1.38*(10-23)
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David Conn VE3KL QCWA Oct. 2004

2. Acknowledgments QCWA Travelers/Committee Croft Taylor VE3CT
Gus Holtz VE3VK
Doug Leach VE3XK
Clare Fowler VE3NPC
Bert Barry VE3QAA
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.
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David Conn VE3KL QCWA Oct. 2004

3. David Conn VE3KL QCWA Oct. 2004
Introduction
A talk about noise levels in amateur radio systems: SSB, CW, PSK31, EME…
Noise Types: Thermal, Shot, Flicker atmospheric, man-made……
Measured with an ideal S meter
Signal Levels
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David Conn VE3KL QCWA Oct. 2004

4. David Conn VE3KL QCWA Oct. 2004
Signal Levels
326 dBm
SUN
124 dBm
Niagara Falls Power Generation
50 dBm
100 Watt Radio Transmitter
-73 dBm
S9 at receiver front end
-144 dBm
Resistor: room temperature (I KHz BW)
Sky background noise (1 KHz BW)
-162 dBm
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David Conn VE3KL QCWA Oct. 2004

5. David Conn VE3KL QCWA Oct. 2004
Noise Types
Thermal: Moving electrons in conductors : KTB
Shot: DC current flow in semiconductors
Flicker or 1/f noise: like earth quakes in devices
Man-made : Can propagate via ionospheric skip
Atmospheric/ionospheric/sky……..
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David Conn VE3KL QCWA Oct. 2004

6. Thermal Noise Power = KTB -144 dBm (290 K, 1 KHz BW)
Amplifier G=1
Noiseless
Bandpass Filter
B = bandwidth
Power = KToB Watts
Resistor at Temperature To
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David Conn VE3KL QCWA Oct. 2004

7. Noise Figure, F Effective Temperature Te
Amplifier G=1
Noisy
Bandpass Filter
B = bandwidth
Power = FKToB
= K(To +Te)B
Resistor at Temperature To
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David Conn VE3KL QCWA Oct. 2004

8. Noise Figure Or Noise Temperature Can use either to measure receivers
F = 1 +Te/To
Moon Temperature
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David Conn VE3KL QCWA Oct. 2004

9. Noise Temperature Moon, Sky, Ground
Antenna
Ideal Receiver
Thermal Radiation
Po = KTmB Tm
Moon
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David Conn VE3KL QCWA Oct. 2004

10. David Conn VE3KL QCWA Oct. 2004
Thermal Noise …Moon
Credit:
Credit:
Moon Temperature 510 K Oct 17, 2004: dBm (1KHz)
Varies with time: 510 K is poor for EME Communications
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David Conn VE3KL QCWA Oct. 2004

11. Examples of Noise Levels
Application
Noise Figure Te
Power (dBm) (1 KHz)
Microwave
3 dB
290
-144 dBm HF
53 dB
57,000,000
-121 dBm….S1
Low Noise Applications
0.7 dB
50 K
-151 dBm
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David Conn VE3KL QCWA Oct. 2004

12. David Conn VE3KL QCWA Oct. 2004
HF Man-Made Noise
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
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David Conn VE3KL QCWA Oct. 2004

13. David Conn VE3KL QCWA Oct. 2004
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
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David Conn VE3KL QCWA Oct. 2004

14. David Conn VE3KL QCWA Oct. 2004
Definition of Terms
S is the reading on an S meter.
Field strength (Volts/m) is a measure of the electric field strength at the receiver
Aeff is the effective area of a lossless antenna, related to directivity
We need to use four terms
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David Conn VE3KL QCWA Oct. 2004

15. The Radio Model: Signal and Noise
Ionosphere Г
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
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David Conn VE3KL QCWA Oct. 2004

16. 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
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David Conn VE3KL QCWA Oct. 2004

17. 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
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David Conn VE3KL QCWA Oct. 2004

18. Man-Made Noise Analysis
Data from ITU-R P Report
Man-made noise relative to thermal noise. Not dependent on the bandwidth
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.
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David Conn VE3KL QCWA Oct. 2004

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!
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David Conn VE3KL QCWA Oct. 2004

20. David Conn VE3KL QCWA Oct. 2004
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
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David Conn VE3KL QCWA Oct. 2004

21. David Conn VE3KL QCWA Oct. 2004
Noise In CW : BW = 500 Hz
CW is better: less than S5
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David Conn VE3KL QCWA Oct. 2004

22. 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
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David Conn VE3KL QCWA Oct. 2004

23. David Conn VE3KL QCWA Oct. 2004
Noise in PSK31 BW = 62.5 Hz
PSK is better: S3
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David Conn VE3KL QCWA Oct. 2004

24. Solutions to the Noise Problem
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?
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David Conn VE3KL QCWA Oct. 2004

25. Filter External Cable Noise: Use 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
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David Conn VE3KL QCWA Oct. 2004

26. David Conn VE3KL QCWA Oct. 2004
Summary
Man-made Noise Dominates at MF/HF
EME requires low temp receivers
No need for very low noise receivers at HF
HF receivers need high dynamic range
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David Conn VE3KL QCWA Oct. 2004

27. Thanks for Attending 73 David
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David Conn VE3KL QCWA Oct. 2004

28. Following are back up slides
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David Conn VE3KL QCWA Oct. 2004

29. 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
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David Conn VE3KL QCWA Oct. 2004

30. 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
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David Conn VE3KL QCWA Oct. 2004

31. David Conn VE3KL QCWA Oct. 2004
Effective Area
As we see later the effective area of a satellite dish is closely related to its physical area
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David Conn VE3KL QCWA Oct. 2004

32. 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
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David Conn VE3KL QCWA Oct. 2004

33. David Conn VE3KL QCWA Oct. 2004
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
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David Conn VE3KL QCWA Oct. 2004

34. 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
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David Conn VE3KL QCWA Oct. 2004