DOPPLER DIRECTION FINDER RADIO DIRECTION FINDER KIT Ramsey Electronics Model No. DDF1 Get in on the fun of radio direction finding (RDF) with this super kit ! The latest in affordable Doppler direction finding equipment available in a complete kit form ..this one even includes the receiving antenna. A must for the “fox hunter” at an unheard of price! Elegant and cost effective design thanks to WA2EBY ! Featured in May / June 1999 QST Articles.
PARTIAL LIST OF AVAILABLE KITS: RAMSEY TRANSMITTER KITS · FM10A, FM25B, FM30, FM Stereo Transmitters · FM100B, FM35 Professional FM Stereo Transmitters · AM1, AM25 AM Broadcast Band Transmitters RAMSEY RECEIVER KITS · FR1 FM Broadcast Receiver · AR1 Aircraft Band Receiver · SR2 Shortwave Receiver · SC1 Shortwave Converter RAMSEY HOBBY KITS · LBC6K Laser Beam Communicator · SG7 Personal Speed Radar · SS70C Speech Scrambler/Descrambler · TT1 Telephone Recorder · LLS1 Laser Light Show · MD3 Microwave Motion De
Ramsey Publication No. MDDF1 Price $5.00 INSTRUCTION MANUAL FOR DOPPLER RADIO DIRECTION FINDER TABLE OF CONTENTS Introduction to the DDF1 .............................................. 4 Theory Of Operation ...................................................... 4 Circuit Description......................................................... 7 Parts List ...................................................................... 11 Learn-as-you-build .......................................................
INTRODUCTION Radio direction finding is a fascinating hobby that has been becoming more and more popular in today's portable world. More recently, Doppler “df-ing” has become the rage, with a display that gives you a direct bearing on the location of the transmitter. Pretty neat trick considering you don’t need multiple separate receivers at different locations to triangulate on the mystery transmitter.
c = Speed of light We can calculate how fast the antenna must rotate in order to produce a given Doppler frequency shift with the following equation fr = dF x 1879.
The frequency of rotation is: fr = 500 x 1879.8/146 x 13.39 A rotation frequency of 480 Hz translates to 480 x 60 = 28,800 or almost 30,000 r/min, which pretty much rules out any ideas of mechanically rotating the antenna! Fortunately, Terrence Rogers, WA4BVY, proposed a clever method of electrically spinning the antenna that works very well. Roger's project, the DoppleScAnt, uses eight 1/4- vertical whips arranged in a circular pattern. Only one antenna at a time is electrically selected.
latches the direction indicating LED. The adjustable delay is used to calibrate the LED direction indicator with the actual direction of the transmission.
Three Synchronized Functions The first function derived from binary counter U7 is antenna array spinning. This is accomplished by using the two most significant bits of U7 to run 1 of 4 multiplexer U8. The selected output of U8 (active low) is inverted by buffer U12. The buffered output of U12 (active high) supplies current sufficient to turn on the antenna to which it is connected. (The details of how this is done will be covered later.) Buffer outputs U12A, U12B, U12C and U12D are sequenced in order.
the digital filter. Even if the clock oscillator frequency drifts, the Doppler tone drifts accordingly, but the center frequency of the digital filter follows it precisely because the same clock runs it. Excessive drift in the 8 kHz clock should be avoided, however, because the analog high and low pass filters that precede the digital filter have fixed passband centers of 500 Hz. A drift of +250 Hz on the 8 kHz clock corresponds to +62.5 Hz (250/4) drift in the Doppler tone produced.
with amplitude above 0.11 V peak and C9 recharges via R23. The LED display remains locked by disabling U11's strobe input whenever the Doppler tone is too low for an accurate bearing. This is done by pulling pin 1 of U11 low via D5 when Q2 is turned on. Audio overload indicator D3 tells you that audio clipping of the Doppler tone is occurring. Clipping results if the signal level from the digital filter is too high and can produce an erroneous bearing indication.
DDF1 PARTS LIST Sort and “check off” the components in the boxes provided. It’s also helpful to sort the parts into separate containers (egg cartons do nicely) to avoid confusion while assembling the kit. Leave the IC’s on their foam holder until ready for installation. RESISTORS AND POTENTIOMETERS 2 2 4 1 7 1 2 1 19 2 1 3 1 2 47 ohm (yellow-violet-black) [R42,51] 330 ohm (orange-orange-brown) [R17,25] 470 ohm (yellow-violet-brown) [R46,47,48,49] 3.
SEMICONDUCTORS AND INTEGRATED CIRCUITS 11 1N4148 small signal diode (small glass case with banded end) [DDF1 board D1,2,5 ANTINT-1 board D1,2,3,4 ANTMTG-1 board 1 ea.
1 Main PC board (DDF-1) 1 Antenna switch board (ANTINT-1) 4 Antenna boards (ANTMTG-1) REQUIRED ITEMS (But Not Supplied) 1 Length of RG58 cable for connecting between your radio and the DDF1.
DDF1 DOPPLER DIRECTION FINDER ASSEMBLY STEPS IMPORTANT!! Although we know that you are anxious to complete the assembly of your direction finder kit, it will become necessary to assemble in a specific order to accomplish the final components installation of your unit. Try to avoid the urge to “jump ahead” installing components. We’ll be installing components in blocks of the same type and/or value.
6. Install R37, 10K ohm. 7. Install R27, 10K ohm. Locate nineteen(19) 33K resistors [orange-orange-orange] 8. Install R5, 33K ohm. 9. Install R11, 33K ohm. 10. Install R12, 33K ohm. 11. Install R6, 33K ohm. 12. Install R9, 33K ohm. 13. Install R10, 33K ohm. 14. Install R1, 33K ohm. 15. Install R3, 33K ohm. 16. Install R2, 33K ohm. 17. Install R7, 33K ohm. 18. Install R31 33K ohm. 19. Install R30, 33K ohm. 20. Install R20, 33K ohm. 21. Install R45, 33K ohm. 22.
Locate two(2) 47 ohm resistors [yellow-violet-black] 34. Install R51, 47 ohm. 35. Install R42, 47 ohm. Locate two(2) 330 ohm resistors [orange-orange-brown] 36. Install R25, 330 ohm. 37. Install R17, 330 ohm. Locate two(2) 22K ohm resistors [red-red-orange] 38. Install R8, 22K ohm. 39. Install R32, 22K ohm. Locate two(2) 68K ohm resistors [blue-gray-orange] 40. Install R33, 68K ohm. 41. Install R29, 68K ohm. Locate 0ne(1) 3.3K resistor [orange-orange-red] 42. Install R14, 3.
DDF-1 MAIN BOARD PARTS LAYOUT DIAGRAM DDF1 17
Locate the two(2) 555 time IC’s 52. Install U6, 555 timer IC. 53. Install U4, 555 timer IC. Locate the 74HC4051 IC 54. Install U5, 74HC4051 IC. Locate the 74HC42 IC 55. Install U8, 74HC42 IC. Locate the 7805 three lead voltage regulator 56. Install VR1, 7805 voltage regulator IC. Install as shown in the diagram by carefully pre-bending the component leads at right angles to the IC. The component should fit flush to the printed circuit board. Solder all three leads.
68. Install C2, .01uF capacitor. 69. Install C3, .01uF capacitor. 70. Install C1, .01uF capacitor. 71. Install C18, .01uF capacitor. 72. Install C19, .01uF capacitor. 73. Install C38, .01uF capacitor. Locate fifteen(15) .1uF capacitors [marked 104] 74. Install C7, .1uF capacitor. 75. Install C51, .1uF capacitor. 76. Install C54, .1uF capacitor. 77 Install C53, .1uF capacitor. 78. Install C52, .1uF capacitor. 79. Install C21, .1uF capacitor. 80. Install C14, .1uF capacitor. 81.
Locate two(2) 100uF capacitors [100uF] 90. Install C30, 100uF electrolytic capacitor. 91. Install C29, 100uF. electrolytic capacitor. Locate three(3) 1uF capacitors [1uF] 92. Install C8, 1uF electrolytic capacitor. 93. Install C25, 1uF electrolytic capacitor. 94. Install C32, 1uF electrolytic capacitor. Locate one(1) 10uF capacitor [1uF] 95. Install C33, 10uF electrolytic capacitor. Locate one(1) .47uF capacitors [.
CONTROL AND DIRECTION INDICATOR ASSEMBLY In these assembly steps for the DDF1 main board, the components will be mounted to the SOLDER SIDE of the circuit board. That’s the other side of the board from the previous steps and with the least amount of printing on it. Make sure the cover with the sticker you applied is dry and the sticker is firmly attached before starting this part of the assembly. 100. Find the 3 DPDT slide switches.
105. Temporarily fit the circuit board into the case top, and carefully tip the board and case over and allow the LED’s to fall into their respective holes in the case. 106. With the 19 LED’s correctly oriented and set to the correct height, solder into place while the circuit is in the case top. Be carefuf and don’t touch the hot soldering iron to the case top. Doing so not only makes boo -boos in the case but is also smelly. 107. Install J1, the 2.1mm DC input connector.
DDF-1 ANTENNA SCHEMATIC DIAGRAM DDF1 25
ANTMTG BOARD LAYOUT ANTINT BOARD LAYOUT DDF1 26
ANTENNA SYSTEM ASSEMBLY Roll those sleeves back up; we’ll get to the antenna switcher and individual antenna assemblies to complete the Doppler DF kit. Have a look at the ANTINT-1 and ANTMTG-1 circuit boards. Note that these circuit boards will be operating at RF frequencies and proper assembly techniques (i.e. short component lead lengths, coaxial cable connections, etc.) will be critical on these boards.
COAXIAL CABLE PREPARATION AND ASSEMBLY We’re getting very close to the end now! It is time to install the coaxial “jumpers” that connect the antenna switcher board to the individual antenna assemblies. To begin our preparation, locate the length of mini coax included with your kit. 1. Cut four 13 inch pieces of cable to connect the switcher to each antenna assembly. 2. “Prep” each of the coaxial cables as shown in the diagram.
Locate the 4 antennas, 5 plastic caps, 4 lock washers, 4 M3 kepnuts, 4 M3 screws 4 antenna boards and 1 antenna switch board.. Refer to the following diagram and perform the following steps on each of the 4 antenna mounting boards. Final Antenna Board Assembly Use the picture on Page 30 as a guide to construct the antenna. 1. Insert an M3 screw through the center hole from the back of the antenna board. 2. Place a #4 internal tooth wash over the screw. 3.
labeled “ANT1” on the ANTINT board. 5. In the same way connect the wires connected to the DB9 connector pins 2, 3, and 4 to the “ANT2”, “ANT3” and “ANT4” respectively. 6. Connect the wire from pin 5 on the DB9 connector to the “GND” pad located near the “ANT4 IN” connection on the ANTINT board. 7. Verify that you have connected the control cable wires correctly. If they are not connected properly your DDF1 will not indicate the right direction of the elusive transmitter you are trying to find. 8.
TESTING Basic Testing It is wise to review your workmanship, looking for circuit shorts or opens prior to applying power. Use an ohmmeter to measure the resistance between power and ground; the value should be greater than 2k ohms. Apply 12 VDC to the RDF unit with the power supply current limited to 150mA to prevent damage in the event of a problem (normal current drain is 100mA).
Direction Indicator Adjust the frequency of the audio generator very slowly around 500 Hz while observing the LED display. You should see the direction indicating LEDs around the green center LED illuminating. The LED illumination should rotate clockwise when the frequency of the generator is set slightly lower than the antenna rotation frequency. (Only one LED will be on when the frequency of the generator equals the antenna rotation frequency.) The display should rotate counterclockwise.
and should be positioned to the right of antenna 1 as viewed from the center of the antennas for a clockwise spin. Close and open S2 until the voltage on terminal J2 pin 3 reads +1.4V. Pins 1,2, and 4 should all read near 0V. Pin 3 is the antenna enable signal for antenna 3 and should be positioned to the right of antenna 2 as viewed from the center of the antennas. Close and open S2 until the voltage on terminal J2 pin 4 reads +1.4V. Pins 1, 2, and 3 should all read near 0V.
Operation Checking performance of the RDF unit is best done in a large, empty area away from tall buildings: a parking lot will do. Use caution at all times during open road operation of the RDF unit. Use a minimum of two people for all testing and operation of the RDF unit: one to operate the vehicle and the other to operate the RDF unit. The magnets securing your antennas to the roof of the car were designed for use at reduced speeds.
Final Calibration A more accurate calibration can be achieved while the car is in motion. Position a volunteer with a transmitter in a safe spot on the side of a long, straight and vacant roadway about 1/4 to 1/2 mile away. Have them transmit on low power (up to 5W) while traveling towards them. The RDF operator should calibrate the RDF display to indicate 0 degrees as straight ahead.
FINAL CASE UP OK… Now that you’ve completed testing and setting up your DDF1 it’s time to make it look pretty. This is the final phase of you trip. CASE ASSEMBLY 1. Place the main circuit board in the top half of the case and secure it in place using the 8 4-40x1/4 inch screws. 2. Notice that the bottom of the case has a bunch of holes drilled in it. Find the speaker and mount it over the holes using the 2 black 6-32 screws and 6-32 nuts. Tighten the screws in place. 3.
CONCLUSION We sincerely hope that you enjoy the use of this Ramsey product. As always, we have tried to compose our manual in the easiest, most “user friendly” format that is possible. As our customers, we value your opinions, comments, and additions that you would like to see in future publications. Please submit comments or ideas to: Ramsey Electronics, LLC Attn.
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THE RAMSEY KIT WARRANTY 1. GENERAL: Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too! All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual is your assurance that prior to release of this kit, a varied group of knowledgeable people have assembled this kit from scratch using this manual.
ABREVIATED TABLE OF CONTENTS Introduction to the DDF1 .................... 4 Theory Of Operation .......................... 4 Parts List ........................................... 11 DDF1 Assembly Steps ...................... 14 Component Layout ............................ 17 Schematic Diagram ........................... 18 Operation........................................... 34 Ramsey Warranty .............................
