beacon transmitter for wspr communication

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.