Montréal Doppler III by Jacques VE2EMM

1. Montréal Doppler III by Jacques VE2EMM by Réal VE2DSK and Serge VE2HLS, May 2005

2. History of the Doppler The principles behind the Doppler or Doppler Direction Finding was first discovered by Austrian physicist Christian Doppler in the nineteenth century. He published his findings in an essay entitled “On the Colored Light of the Double Stars and Certain Other Stars of the Heavens” in 1842. The Doppler effect is readily observed in sound waves, as you have surely noticed when a train passes you with the horn sounding. The pitch suddenly drops as the engine passes by. The effect occurs when the distance between a source emitting a wavelength and one that is receiving it is changing, as they are approaching the wavelength appears to be shortening and as they draw apart the wavelength gets longer. The principles behind the Doppler Effect holds true not only for sound but also for light and all forms of electromagnetic radiation including (Radio waves). The first description of a Direction Finder goes all the way back to 1947 by H.T. Budenbom who used the Doppler modulation with the assistance of a rotary system of antenna. Today, there is more than 300 inventions or patents recorded using Doppler's system throughout the various layers of the electromagnetic spectrum.

4. Doppler Direction Finder for Amateur Radio began in 1978 when Terence Rogers (WA4BVY) wrote an article in QST about a practical unit using 16 leds for the 2 meters band. Other systems with 32 and 36 leds made their appearance on the market using CMOS and TTL logic technology. W6AOP sold several kits using the CMOS version only. In 1981 several commercial firms began selling various products for the Amateur Radio community, like the Dick Smith Doppler Direction Finder. A VHF Doppler system made with integrated circuits was designed by Chuck Tavaris (N4FQ). Conceived to be the simplest possible and the least expensive, this system was called Roanoke after Chuck's (N4FQ) home town of Roanoke Virginia, USA. Here in Montreal Jacques (VE2EMM), user of a PIC microcontroller produced by the Microchip company, improved the existing Doppler system by adding several options that makes the Montreal Doppler 3 a very interesting project.

5. The characteristics

6. 1 The MTL Doppler 3 has a 36 led display. When the center led is green the direction is good, and when it’s red it means that there's no signal, the last good bearing stays on until the next new signal.

7. 2 Three PICs microcontrollers are used, a 16F628A for the display, a 16F877A for the main circuit and a 12F675 as a frequency divider

8. 3 Two audios filters are used, the max 267 is the best pass band filter and it's simple to use, it’s followed by the original filter Roanoke which has a very narrow total band-width (+/- 0.5Hz)

9. 4 The Doppler II phase integration and detection software is used

10. 5 A LM386 is used as an audio amplifier that's independent of the Doppler

11. 6 A simpler menu selection is used, turn a button to choose and press the switch "to activate"

12. 7 It can be used with 4 antennas commutated towards +V or - V or out of differential like 8 antennas +/-

13. 8 Activating the switch sends the direction towards APRS. The protocol is: CR><LF>%359/Q<CR><LF> Q (0<8) and is the quality of the signal taken right before the extraction of the phase

14. 9 The information of the GPS passes through the Doppler and stops when the direction is sent to a PC

15. The 16 menus :

16. Menu 0 During normal operation, the push-button starts only one transmission towards the PC and the APRS (This menu is optional, August 14 04) The first line displays : The QUALITY FACTOR (amplitude of the signal on the outlet side of the integrator), and the DIRECTION in degree and the number of at present accumulated returns. The second line posts : A bar-graph of the signal present on the outlet side of the first filter of the Doppler or the signal of the S-Meter of your radio.

17. Menu 1 Normal operation, the pushbutton alternates between integration and no integration. The first and the second line displays the same data as in menu #0

18. Menu 2 Reduction of the integration

19. Menu 3 Increase of the integration

20. Menu 4 Automatic calibration forwards the car

21. Menu 5 Manual reduction of the calibration

22. Menu 6 Manual increase of the calibration

23. Menu 7 Selection of the minimum factor of quality(0<8), the direction is displayed for this value and more. If the quality decreases, the display freezes with the last good direction.

24. Menu 8 Future Menu

25. Menu 9 Future Menu

26. Menu 10 Baud Rate selection for the TX towards the PC, 2400, 4800, 9600, 19200

27. Menu 11 Two choices for the bar-graph, the S-Meter or the exit level of the MAX267 filter

28. Menu 12 There is three calibrations choices for various receivers and/or cars

29. Menu 13 Antennas rotation selection, CW or CCW

30. Menu 14 Two antennas choices 4 + or - and 4 differentiels of 8 antennes + or -

31. Menu 15 Choice of the antenna under test (each antenna can be activated individually)

32. The participants Alex VE2AMT - Claude VE2BLV François VA2FBT - Guy VE2GMP Jacques VE2EMM - Jean VE2JMK Luc VA2LUK - Marcel VE2GMR Martin VE2MJT - Mathieu VE2TMQ Maurice VA2MBR - Maurice VE2MIE Michel VE2TLM - Réal Tremblay Réal VE2DSK - René VA2RDB René VE2MPA - Ronald VE2JOR Serge VE2HLS