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BEACON TRANSMITTER FOR WSPR COMMUNICATION
By:
Rifqi Andi Setiawan
NRP: 1203131051
Advisor:
Ari Wijayanti, ST., MT.NIP: 197612162003122001
Ir. R. Henggar Budiman, MT.NIP: 195810261987011002
BACKGROUND
Difficult to establish link
HF (High Frequency) Communication
ProblemUnderstanding HF
propagation characteristics
Ionospheric Condition
Solution
Using WSPR (Weak Signal Propagation Reporter)
How ?
Emergency Communication
Fig 1. Background
OBJECTIVE
• Build beacon transmitter for WSPR communication – based Raspberry Pi
• Broadcast WSPR Signal
• Knowing the results report of WSPR signal.
PROBLEMS
Problems:
• How to find out the wave propagation characteristics of HF?
• How to monitor signal reception quality HF remotely in real-time?
• Does time affect the quality of signal reception?
• How to build own WSPR transmitter?
LIMITATIONS
• HF band used in this study is at 80 meters (3.5941 MHz).
• System of WSPR signal generation at the transmitter is built based on existing software.
• Broadcast WSPR signal and data observation report conducted for 24 hours.
WHAT IS WSPR ?
Fig 2. WSPR mapping feature(http://wsprnet.org/drupal/wsprnet/map)
WSPR (Weak Signal Propagation Reporter) is an amateur radio communications protocol performed by sending and receiving low-power signals in order to determine the potential of radio wave propagation path at MF (Medium Frequency) and HF(High Frequency) band. WSPR was created by an American Astrophysics Joseph Hooton Taylor, Jr.
Database Server
(wsprnet.org)
Transmit Station
Receive Station
Ionosphere Wave
BeaconBeacon
Receiving beacon data and measuring signal
ReportingViewing
Transmitting beacon data (callsign + location + power)
Fig 3. WSPR Works
HOW WSPR WORKS ?
WSPR EQUIPMENT
This Project(build own transmitter)
Replacedwith
Fig 4. WSPR general equipment
WSPR PROTOCOL
Band Dial frequency (MHz)
Tx frequency (MHz)
80m 3.592600 3.594000 - 3.594200
60m 5.287200 5.288600 - 5.288800
40m 7.038600 7.040000 - 7.040200
30m 10.138700 10.140100 - 10.140300
20m 14.095600 14.097000 - 14.097200
17m 18.104600 18.106000 - 18.106200
15m 21.094600 21.096000 - 21.096200
12m 24.924600 24.926000 - 24.926200
10m 28.124600 28.126000 - 28.126200
This project focus
Fig 5. WSPR signal format Fig 6. WSPR frequency allocation
WSPR ON RASPBERRY PI
• A programmer Daniel Ankers from Isle of Man , United Kingdom once published an open source program code named " WsprryPi " used in the Raspberry Pi to be able to generate signals WSPR directly through pin GPIO ( General Purpose Input Output ).
• Currently , the latest development of the " WsprryPi " is done by a programmer James Peroulas from USA with the addition of features such as automatic frequency calibration using the NTP ( Network Time Protocol ).
SYSTEM DESIGN
Low Pass Filter
Raspberry Pi
20x4 LCD
Push Button
USB KeyboardSignal Generator
GPIO04 Pin Output
Power Amplifier
(a)
(b)
(c)
(b)
Fig 7. System Design
SYSTEM DESIGN
Fig. 8 Signal generator interface connection
Homescreen
Button 2 = true
Button 1 = true
Button 3 = true
Button 4 = true
Input message(Callsign, Power,
Grid locator)
Y
tx_proc = call WsprryPi with
message parameter
Tx repeat (Enable/Disable)
tes_proc = call
program WsprryPi to test at 3,6 MHz
Y
tx_proc = active
Stop tx_proc
N
Y
Y
A
test_proc = active
Y
Stop test_pr
oc
Y
Message.txt
message.txt
N
A
Start
Button check
A A A A
N N N N
Save ?
YN
Fig. 9Signal generator interface program flowchart
SYSTEM DESIGN
𝑅𝐿′ =(𝑉𝑆−𝑉𝑘𝑛𝑒𝑒)
2 . 𝑃𝑜
2
𝑋𝑅𝐹𝐶 = 10. 𝑅𝐿
Where,
Vs = Source voltage
Vknee = Knee voltage transistor
RL’ = Optimum load impedance
RL = Load impedance
VQ = Transistor voltage (VCE if bipolar, VDS if FET)
Po = power output
XRFC = impedance of RFC (Radio Frequency Choke)Fig 10. Basic RF amplifier circuit
SYSTEM DESIGN
𝐴𝑘 =2 sin 2𝑘 −1 𝜋
2𝑛, 𝑘 = 1, 2, … , 𝑛
(4)
𝐿𝑘 =𝑅𝐿 .𝐴𝑘
2.𝜋.𝑓𝑐, 𝑘 = 𝑒𝑣𝑒𝑛
(5)
𝐶𝑘 =𝐴𝑘
2.𝜋.𝑓𝑐.𝑅𝐿, 𝑘 = 𝑜𝑑𝑑
Where,
Ak = Reactance k from Butterworth low pass filter
n = Butterworth filter order
Lk = induktive k component from Butterworth low pass filter
Cn = capacitive k from Butterworth low pass filter
fc = cut-off frequency
RL = load lmpedance
Fig 11. Cauer Topology Butterworth low pass filter
SYSTEM TEST AND RESULT
𝜂 =𝑃𝑑𝑐
𝑃𝑟𝑓. 100%
𝜂 =0,5
1. 100%
𝜂 = 50%
Efficiency:Pdc = 0,2*5 =1 Watt
Fig 12. Power Amplifier test
Prf = 0,5 Watt
(c)(a)
(a)
SYSTEM TEST AND RESULT
Fig 13. low pass filter response test
(a)
(b)
cut-off (-3dB or 0,707 times)
So, Vpeak (cutoff) = Vpeak *0,707= 0,7 ∗ 0,707 = 0,5 𝑉𝑝 (at 3,9 MHz)
SYSTEM TEST AND RESULT
Fig 14. signal form test
Volt/div = 1, time/div = 100 ns
Volt/div = 2, time/div = 100 ns
Volt/div = 2, time/div = 100 ns
WSPR TEST
Fig 15. WSPR indoor test
(a)
(c)
Decoded signal
(b)
WSPR TEST
Fig 16. WSPR outdoor test
(a)
(b)
(c)
WSPR REPORT RESULT
Reporter callsign
Grid locator Distance AzimuthNumber
of Country
DF5FH JO42um 11532 322o 4 German
OZ7IT JO55df 11336 325o 1 Denmark
R0AU NO66ed 7297 348o 4 Russia
VK3BL QF22 4671 141o 76 Australia
VK4ECW QG62ll 4787 123o 199 Australia
VK6XT OF86 2950 172o 60 Asutralia
VK8RD PH57ko 2061 107o 28 Australia
Fig 17. Reporter list
Fig 18. Number of report
DF5FH OZ7IT ROAU VK3BL VK4ECW VK6XT VK8RD
17:00 - - - - - -19.877 -25
18:00 - - - - - -16.64 -22
19:00 - - - - -20.14491 -14.015 -19.162
20:00 - - - -27.136 -15.36114 -8.1244
21:00 - - - -25.243 -12.92802 -5.5272 -15.162
22:00 - - - -24.844 -12.4348 -4.6407 -12.698
23:00 - - - -24.571 -11.24791 -7.6284 -15
0:00 - - - -24.228 -10.39876 -8.261 -9.6983
1:00 -26 - -24.94 -22.562 -12.95888 -5.5541 -8.3619
2:00 -26.471 -25 - -25.722 -14.23345 -10.499 -11.471
3:00 - - - -30 -15.17235 -14.728 -9.8859
4:00 - - - - - -16.974 -12.924
5:00 - - - - - -14.086 -18
6:00 - - - - - - -
7:00 - - - - - - -
8:00 - - - - - - -
9:00 - - - - - - -
10:00 - - - - - - -
11:00 - - - - - - -
12:00 - - - - - - -
13:00 - - - - - - -
14:00 - - - - - - -
15:00 - - - - - - -
16:00 - - - - - - -24
SNR Average (dB)Hour
Fig 19. Hourly SNRdb [in table] Fig 20. Hourly SNRdb [in chart]
WSPR REPORT RESULT
CONCLUSION
• Power amplifier that has been designed, when tested have efficiency of 50% with an output power of 0.5 Watt.
• Low pass filter has been designed, when tested had a cut-off frequency at 3.9 MHz and managed to eliminate the frequency harmonics of the output power amplifier
• After the broadcast signal WSPR for 24 hours, got range right time to get a signal report WSPR for 80 meter band which occurred at 16:00 until 5:00.
• In the results report WSPR, SNR values WSPR audio signals received by the receiver reaches its peak at 22:00 until 1:00, so at this time is the best condition of the ionosphere channels.
REFERENCE
• Bowick, Chris, “RF Circuit Design”, Massachusetts, Newnes, 1997.
• C. Cripps, Steve, “RF Power Amplifiers for Wireless Communications”, Massachusetts, Artech House Inc., 2006.
• Lutz, Mark, “Programming Python”, Massachusetts, O’Reilly Media Inc., 2009.
• Joe Taylor, Bruce Walker, “WSPRing Around the World”, ARRL, 2010, pp 1-3.
• Joe Taylor, “WSPR 3.0 User’s Guide”, Princeton University, United State of America, 2011, pp 16-17
• Paul Harden, “Transmitter (PA) Output Filter”, Atlanticon QRP Forum, 2002, pp. 1.
• Onno W. Purbo, “Buku Pegangan Amatir Radio Pemula & Siaga”, Jakarta, Indonesia, 2007, pp. 32-38.
• Peroulas, James. (2015, Oct. 2). Raspberry Pi WSPR transmitter using NTP based frequency calibration [Online]. Available: https://github.com/JamesP6000/WsprryPi.
• Ankers, Daniel .(2013, April 9). Bareback LF/MF/HF/VHF WSPR transmitter using a Raspberry Pi [Online]. Available: https://github.com/threeme3/WsprryPi.
• Talbot, Andy. (2009). The WSPR Coding Process [Online]. Available: http://www.g4jnt.com/Coding/WSPR_Coding_Process.pdf.
• Butterworth filter. Retrieved 20 December 2015, from https://en.wikipedia.org/wiki/Butterworth_filter.
• Raspberry Pi. Retrieved 15 December 2015, from https://en.wikipedia.org/wiki/Raspberry_Pi.
• Turning the Raspberry Pi into an FM Transmitter. Retrieved 5 January 2016, from http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Rasberry_Pi_Into_an_FM_Transmitter.
