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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 1879.8/R x fc where fr = The frequency of the received signal in megahertz dF= The Doppler shift in Hertz R = Radius of antenna rotation in inches fc = Carrier frequency of the received signal in megahertz As an example, let's calculate how fast the antenna must rotate in order to produce a Doppler shift of 500 Hz at 146 MHz, assuming the antenna is turning in a circle with radius 13.39 inches.

R F S ig na l (fo )

F ig ure 1

D R o ta tio n C A

-f (B )

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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. By controlling the order in which the antennas are selected, the DoppleScAnt emulates a single 1/4 whip antenna moving in a circle. A clever feature in Roger's design is the use of a digital audio filter to extract the Doppler tone from voice, PL tones and noise. The DDF1 design offers slightly improved audio filtering, 74HC-series logic circuits capable of driving the LED display directly, a wideband VHF/UHF antenna switcher and the four 1/4- mag-mount antennas. Total project cost is about one third the cost of purchasing a commercial RDF unit - and building the project is a lot more educational. HOW IT WORKS To understand the operation of the Doppler RDF circuit, see the block diagram of Figure 2. An 8 kHz clock oscillator drives a binary counter. The output of the counter performs three synchronized functions: "spin" the antenna, drive the LED display and run the digital filter. The counter output drives a 1 of 4 multiplexer that spins the antennas by sequentially selecting (turning on) one at a time in the order A,B,C,D,A, etc., at 500 times per second. The counter output also drives a 1 of 6 multiplexer used to drive the LED display in sync with the spinning antenna. The RF signal received from the spinning antenna is connected to the antenna input of a VHF or UHF FM receiver. The spinning antenna imposes a 500 Hz frequency deviation on a 146 MHz received signal. A 146 MHz FM receiver connected to the spinning antenna's RF output demodulates the 500 Hz frequency deviation and sounds like a 500 Hz tone with loudness set by the 500 Hz frequency deviation. The receiver audio, including 500 Hz Doppler tone, is processed by a series of audio filters. A high pass filter rejects PL tones and audio frequencies below the 500 Hz Doppler tone. A low-pass filter rejects all audio frequencies above the 500 Hz Doppler tone, and a very narrow bandwidth digital filter extracts only 500 HZ Doppler tone. The output of the digital filter represents the actual Doppler frequency shift

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Figure 2 Block Diagram of the WA2EBY Doppler RDF System Antenna Switcher 1 of 4 Data Selector

LED Compass Display

8 KHz Clock

Binary Counter

1 of 16 Data Selector Latch

High Pass Filter AF Out

Low Pass Filter

Digital Filter

Zero Crossing Detector

Adjustable Delay

R 36 Calibrate FM Receiver External Speaker
shown in figure 1. - Zero crossings of the Doppler frequency shift pattern correspond to the antenna position located directly toward the source of transmission (position A) or directly opposite the source of transmission (position C). The zero-crossing signal passes through an adjustable delay before it latches the direction indicating LED. The adjustable delay is used to calibrate the LED direction indicator with the actual direction of the transmission. CIRCUIT DESCRIPTION Take a look at the schematic of the WA2EBY Doppler RDF on page 18. The heart of the system is an 8 kHz clock oscillator built around a 555 timer, U4, configured as an astable multivibrator. C26, R27, and R28, R29 determine the multivibrator's oscillation frequency. R27 and R28 are series connected to allow fine tuning the oscillation frequency to 8 kHz. It is important that the clock frequency be exactly 8 kHz; I recommend that it be adjusted to +/-250 Hz of that frequency for reasons that I'll discuss shortly. The 8 kHz output of U4 provides the clock for 4 bit binary counter U7. The 3 bit binary coded decimal (BCD) output of U7 is used to operate three synchronized functions.

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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 corresponding buffer selects antennas A,B,C,D,A,B, etc. Driving multiplexer U8 with the two most significant bits of counter U7 divides the 8 kHz clock by four, so each antenna is turned on for 0.5 ms. One complete spin of the antenna requires 0.5 ms x 4 = 2.0 ms, thus the frequency of rotation is 2 ms or 500 Hz. An FM receiver connected to the spinning antenna's RF output has a 500 Hz tone imposed on the received signal. Sequencing the 16 LED display is the second synchronized function from binary counter U7. This is done by using the binary output of counter U7 to select 1 of 16 data outputs of U11. The selected output of U11 goes low, allowing current to flow from the +5 V supply through current limiting resistor R51, green center LED D16, and direction indicating red LED's D17 through D32. Each antenna remains turned on as the LED display sequences through four direction indicating LED's, then switches to the next antenna. Each direction indicating LED represents a heading change of 22.5 degrees. The third synchronized function is operating the digital filter responsible for extracting the Doppler tone. The 500 Hz Doppler tone present on the receiver audio output is connected to an external speaker and audio level adjust potentiometer R50. The signal is filtered by a two-pole Sallen Key high pass filter built around op amp U1A. It filters out PL tones and audio frequencies below the 500 Hz Doppler tone. Next, a four-pole Sallen-Key low pass filter using U1B and U1C band limits audio frequencies above the 500 Hz Doppler tone. The band limited signal is then applied to the input of a digital filter consisting of analog multiplexer U5, R18, R19 and C10 through C17. (Readers interested in the detailed operation and analysis of this fascinating digital filter are encouraged to review QEX magazine for June 1999) The Digital Filter Using the three most significant bits of U7 to drive the digital filter divides the 8 kHz clock by the two, making the digital filter code rate 4 kHz. The center frequency of the digital filter is determined solely by the clock frequency divided by the order of the filter. This is an 8th order filter, which makes the center frequency of the filter 4 kHz/8 =500 Hz. This is the exact frequency at which the antenna spins, hence, the same frequency of the Doppler tone produced on the receiver audio connected to the spinning antenna. This is

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truly an elegant feature of the Doppler RDF design. Using the same clock oscillator to spin the antenna and clock the digital filter ensures the Doppler tone produced by the spinning process is precisely the center frequency of 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. This value is acceptable because of the relatively low Q of the analog bandpass filter. Digital filter Q is calculated by dividing the filter's center frequency by its bandwidth (Q=f/BW) or 500 Hz/4 Hz=125. It's very difficult to realize such a high Q filter with active or passive analog filters and even more difficult to maintain a precise center frequency. The slightest change in temperature or component tolerance would easily de-Q or detune such filters from the desired 500 Hz Doppler tone frequency. The digital filter makes the high Q possible and does so without the need for precision tolerance components. By varying damping pot R19, the response time of the digital filter is changed. This digital filter damping helps average rapid Doppler tone changes caused by multipath reflected signals, noise or high audio peaks associated with speech. A digitized representation of the Doppler tone is provided at the digital filter output. A two pole Sallen Key low pass filter built around U2B filters out the digital steps in the waveform providing a near sinusoidal output corresponding to the Doppler shift illustrated in Figure 1B. The zero crossings of this signal indicate exactly when the Doppler effect is zero. Zero crossings are detected by U2C and used to fire a monostable multivibrator (U6) built around a 555 timer. U6's output latches the red LED in the display corresponding to the direction of transmission with respect to the green center LED, D16. Calibration between the actual source of transmission and the red direction indicating LED latched in the display is easily accomplished by changing the delay between the Doppler tone zero crossing (firing of U6) and the generation of the latch pulse to U11. C23, R36 and R37 determine this delay. Increasing or decreasing the delay is achieved by increasing or decreasing the value of the calibrate potentiometer R36. Low Signal Level and Audio Overload Indicators Two useful modifications included in this design are the low signal level lockout and audio overload indicators. U2D continuously monitors the amplitude of the Doppler tone at the input to the zero crossing detector. U2Ds output goes low whenever the Doppler tone amplitude drops below 0.11 V peak. This is done by referencing the negative input of U2D to 2.39 V, 0.11 V below the nominal 2.5 VDC reference level output of U2B by means of voltage

REQUIRED ITEMS (Not Supplied) 1 Length of RG58 cable for connecting between your radio and the DDF1. (Not supplied due to unknown length required!)

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RAMSEY Learn-As-You-Build KIT ASSEMBLY There are numerous solder connections on the DDF1 printed circuit board. Therefore, PLEASE take us seriously when we say that good soldering is essential to the proper operation of your direction finder!
Use a 25-watt soldering pencil with a clean, sharp tip. Use only rosin-core solder intended for electronics use. Use bright lighting, a magnifying lamp or bench-style magnifier may be helpful. Do your work in stages, taking breaks to check your work. Carefully brush away wire cuttings so they don't lodge between solder connections.
We have a two-fold "strategy" for the order of the following kit assembly steps. First, we install parts in physical relationship to each other, so there's minimal chance of inserting wires into wrong holes. Second, whenever possible, we install in an order that fits our "Learn-As-You Build" Kit building philosophy. This entails describing the circuit that you are building, instead of just blindly installing components. We hope that this will not only make assembly of our kits easier, but help you to understand the circuit youre constructing. For each part, our word "install" always means these steps: 1. Pick the correct part value to start with. 2. Insert it into the correct PC board location. 3. Orient it correctly, follow the PC board drawing and the written directions for all parts - especially when there's a right way and a wrong way to solder it in. (Diode bands, electrolytic capacitor polar ity, transistor shapes, dotted or notched ends of IC's, and so forth.) 4. Solder all connections unless directed otherwise. Use enough heat and solder flow for clean, shiny, completed connections. 5. Trim or nip the excess component lead wire after soldering.
Enough of that. lets get started!

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DDF1 DOPPLER DIRECTION FINDER ASSEMBLY STEPS Although we know that you are anxious to complete the assembly of your direction finder 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. Please also note that the components will mount on BOTH SIDES OF THE PRINTED CIRCUIT BOARD for proper alignment into the provided case assembly. Since you may appreciate some warm-up soldering practice as well as a chance to put some landmarks on the PC board, well first install some of the larger mounting components. This will also help us to get aquainted with the up - down, left - right orientation of the circuit board. Remember that the majority of the components will be mounted on the component side of the circuit board and soldered on the solder side of the circuit board, the side with the printed circuit traces. Have a look at the component layout diagram to help with your assembly. 1. Install J1, the 2.1 mm DC input connector. Notice that this mounts on the component side of the circuit board and the solder leads push through the circuit board to protrude through the solder pads for connection. Be sure to push the part as close to the circuit board as it will go, as the alignment of this part is important in getting the case holes to line up with the part. Solder all three leads; don't be afraid to use enough heat to flow the entire connection. 2. Identify and install J3, the miniature audio input jack. Gently rock the component into place before soldering. Be sure to solder the mounting tabs into place to provide for a secure fit. 3. In the same manner, identify and install J2, the DB 9 connector, which will output the switching control voltage to the antenna switch. Be sure that the connector fits snugly to the printed circuit board. Solder all 11 connections to the jack, being careful not to bridge solder between the pins. Take your time here as a missed solder connection now can cause an hour of troubleshooting at the completion of your kit. There we go, now were on our way to getting this one put together! Double check your connections, make sure that the jacks are resting snugly on the circuit board, and lets continue. Well get started working on the clock section of our circuit, using a 555 oscillator IC. 4. Moving towards the lower right of the main circuit board (component side view), find the position for U4, one of the 555 timer ICs. Install U4, the 555 timer IC. Make sure to align the notch or dot associated with pin one with the notch shown in the parts layout diagram. Also check to be

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sure all 8 pins are through the board before soldering the IC in place. This IC is responsible for the master clock oscillator for the direction finder unit , and replaces a few dozen discreet components. 5. Install C24,.001uF disc capacitor (marked 102). 6. Install R29, 68K ohm (blue-gray-orange). 7. Install R28, 18K ohm (brown-gray-orange). 8. Install C26,.001uF disc capacitor (marked 102). 9. Install R27, 10K ohm (brown-black-orange). 10. Install R26, 33K ohm (orange-orange-orange). 11. Identify C25, the 1 uF electrolytic capacitor. Electrolytic capacitors are polarized with a (+) and (-) lead and must be installed in the correct orientation. Ordinarily, only the negative side is marked on the capacitor body with a dark band and the (-) sign clearly shown, while the PC boards will usually show the (+) hole location. Use care to ensure proper polarity. See the parts diagram for proper placement. The capacitor should fit snugly down to the PC board. Now its time to build the power supply regulation portion of the circuit. We need a well regulated low noise power supply to enable our circuit to work at peak performance. 12. Identify VR1, the 7805 voltage regulator IC. Install as shown in the diagram by carefully pre-bending the component leads at right angles to the regulator IC. The component should fit flush to the printed circuit board. Solder all three leads. 13. Install electrolytic capacitor C29, 100 uF. Again, this is an electrolytic capacitor and must be mounted with respect to the correct polarity. 14. In the same manner, install C32, 1 uF electrolytic. Watch that polarity! 15. Install C31,.1uF disc capacitor (marked 104). 16. Install R42, 47 ohm (yellow-violet-black). 17. Install C30, 100 uF electrolytic. Be sure to orient the polarity as shown in the diagram. 18. Identify D6, the 1N4002 diode (epoxy case with a polarity band deDDF1 15
noting the cathode (negative) side of the diode. Install as shown in the parts placement diagram (D6 is adjacent to the power switch S1). 19. Moving again towards the lower right of the main circuit board (component side view), find the position for U6, the other 555 timer IC. Install U6, the 555 timer IC. Make sure to align the notch or dot associated with pin one with the notch shown in the parts layout diagram. 20. Install R34, 33K ohm (orange-orange-orange). 21. Install R35, 33K ohm (orange-orange-orange). 22. Install C21,.1uF disc capacitor (marked 104). 23. Install C23,.0047uF disc (marked.0047 or 472). 24. Install R37, 10K ohm (brown-black-orange). 25. Install C22,.001uF disc capacitor (marked 102). Now that wasnt so bad was it! Youve just completed the power supply and oscillator section of your direction finder. Pretty soon you will be searching for fox transmitters in baby strollers at the mall! Lets get back to it. Next well work on the digital filter section of the circuit. Be sure to mount the components as close to the printed circuit board as possible to provide for reliable operation. 26. Install C14,C17,C16,C15, all.1uF disc (marked 104). Now you're starting to roll along. 27. In the same manner, install C10, C12, C11, and C13, again, all.1uf (marked 104). It is time to install some of the logic ICs. Please note that although significant advances have been made in modern day CMOS technology, static precautions should be observed while installing these ICs. Be sure to orient the IC band or notch as shown in the parts diagram for each IC. Try to focus on the individual IC pin as youre soldering and walk the iron to consecutive pins of the IC as you continue. 28. Install U5, the 74HC4051 IC. Make sure not to bridge solder between the pins. 29. Install U8, the 74HC42 IC. Solder all 16 pins. 30. Install U12, the 74HC14 inverter IC. 31. Install U7, 74HC161 IC. Watch that orientation!

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DDF-1 MAIN BOARD PARTS LAYOUT DIAGRAM

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DDF1 18

DDF1 19

32. Install U11, the 24 pin 74HC4515 IC. Make sure all the pins pass through the circuit board before e soldering. Great job so far! Take a moment now to check your previous solder joints for opens where the solder did not completely flow around the connection or solder bridges between closely spaced pads or IC pins. It seems the best time to identify these types of problems is now when youre focused on this section of the board, saving you time to try to rethink your steps later. 33. Install R39, 10K ohm (brown-black-orange). 34. Install R38, 33K ohm (orange-orange-orange). 35. Install R46, 470 ohm (yellow-violet-brown). 36. Install C51,.1uF disc (marked 104). 37. Install R47, 48, and 49, all 470 ohm (yellow-violet-brown). 38. Install disc capacitors C52, 53, and 54, all.1uF (marked 104). That concludes most of the digital circuitry included in your kit, take a moment to recheck your work. Well get started now on the audio processing section of the direction finder kit. 39. Locate the position of C9 in the upper left hand corner of the main circuit board. Install C9,.01uF disc capacitor (marked.01 or 103 or 10nF). 40. Install R23, 220K ohm (red-red-yellow). 41. Identify D2, the 1N4148 small signal diode (marked with a polarity band). Use care to orient the part as shown in the parts diagram, and install in the D2 position. 42. Install R25, 330 ohm (orange-orange-brown). 43. Install R24, 10K ohm (brown-black-orange). 44. Install speaker output jack J4 using the pin connector. 45. Identify and install Q2, the transistor marked 2N3904. The flat side must be placed as shown on the PC board, facing R24. Mount it as close to the board as possible without forcing it. Carefully solder all three leads. 46. Identify and install C33, a 10 uF electrolytic capacitor. Remember

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that electrolytics are polarized and must be mounted as shown in the diagram. 47. Install U3, the 324 op amp. Be sure to point the dot, notch, or band as shown in the parts diagram. Solder all 14 leads 48. Install R15, 220K ohm (red-red-yellow). 49. Install R17, 330 ohm (orange-orange-brown). 50. Moving to the right of J3, Install R43 and 45, both 33K ohm (orangeorange-orange). 51. Install transistor Q1, a 2N3904 type (marked 3904). Be sure to orient the flat side as shown in the parts diagram. 52. Identify and install small signal diode D1, 1N4148 (glass bead type with polarity band). Mount as shown in the parts layout diagram. 53. Install R16, 10K ohm (brown-black-orange). There is another plated through hole inside the silkscreen for R16 that is not the installation hole. Be sure to install the resistor lead in the proper hole. 54. Install C20,.47 uF electrolytic capacitor (marked.47). The banded (negative) side faces R8. 55. Install R8, 22K ohm (red-red-orange). 56. Install C4 and C5, both.01uF disc capacitors (marked.01 or 103). 57. Install R5, 33K ohm (orange-orange-orange). 58. Install R11, another 33K ohm (what were those colors).(orangeorange-orange). 58. Install R12, 56K ohm (green-blue-orange). 59. Install C7,.1uF disc (marked 104). 60. Install C6,.01 disc capacitor (marked.01 or 103 or 10nF). 61. Install R6, 33K ohm (orange-orange-orange). 62. Install R14, 3.3K ohm (orange-orange-red). 63. Install R13, 10K ohm (brown-black-orange).

LED (-)

Leave these leads as long as possible PC Board (+)

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how one lead is longer than the other. The longer of the two leads is the anode, or (+) connection. Most diodes also have a flat molded in the component body. This corresponds to the cathode or (-) side of the part. Note also that while both of the holes is rectangular, only one of the holes has the corners rounded off. The longer (anode) lead belongs in the rounded off hole, and the shorter (cathode) lead belongs in the rectangular (non-rounded) hole. Now for the fun part! When mounting the direction heading LEDs we would like the height of the diodes from the circuit board to be at just the correct height to protrude through the top panel of the unit. The easiest way to accomplish this task is to slide the LEDs into place making absolutely sure that the flat side of the diodes are correctly oriented as seen on the silkscreen. D3, 4, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 are RED LEDs , while D16 is the GREEN LED. Once the LEDs are loosely into place, temporarily fit the circuit board into the case top, and when tipped over the LEDs should fall into their respective holes. 88. With the 19 LEDs correctly oriented and set to the correct height, solder into place. The main board assembly is complete! You are that much closer to a functioning Doppler DF system. Take a break.you have accomplished the biggest chunk of the kit. When we start up again, well be creating an antenna switching system for the direction finder ASSEMBLY INSTRUCTIONS FOR THE ANTENNA SYSTEM Roll those sleeves back up; well get to the antenna switcher and individual antenna assemblies to complete the Doppler DF kit. Have a look at the ANTINT-1 antenna interface board. This is where we will accomplish the solid state switching between each antenna, Please note that this circuit board will be operating at RF frequencies; proper assembly techniques (i.e. short component lead lengths, coaxial cable connections ) will be critical on this board and the antenna assemblies. To minimize these impedance destroying lead lengths, we have opted for a surface mount procedure of the remaining components. Therefore instead of the typical thru hole assembly you have completed on the main board, the components on this assembly will be soldered on the same side of the circuit board. It is necessary to preform the components and trim excess leads prior to the component being installed. 1. Form and install diodes D1, 2, 3, 4 into their respective positions on the circuit board.

Diode Mounting Diagram

Solder Connection Circuit Trace PC Board

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Use the shortest lead length possible. Note that these components are polarized. Install the banded end as shown in the parts diagram. Dont worry about too much heat from your soldering iron; you will not damage the diodes. 2. In the same manner form and install inductors L1, 2, 3, and 4 (brown-red-gold). Keep those lead lengths as short as possible. 3. There are also eight.001uF disc capacitors to be installed. Again, see the diagram for proper placement. Install C1-C8 to the correct tabs on the circuit board. Again, keep the lead lengths as short as possible!

Coil Mounting Diagram

Capacitor Mounting Diagram 102
WHIP ANTENNA AND ANTENNA MOUNTING BOARD INSTRUCTIONS You will need to mount two components as well as an antenna whip to each ANTMTG board 1. Install the 1N4148 diode on the ANTMTG circuit board in the same manner in which you installed them on the switcher, keeping those leads as short as possible. 2. Install the 1.2 uH coil in the proper position. 3. Repeat the steps for the remaining three circuit board assemblies. COAXIAL CABLE PREPARATION AND ASSEMBLY Were 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.

Tinned Braid

1. Cut four 13 inch pieces of cable to connect the switcher to each antenna assembly.

RG-174 Coax

Center Conductor

Center Insulation

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2. Prep each of the coaxial cables as shown in the diagram. Be careful not to use too much heat when tinning the braid of the coax as this could damage the center insulating shield. 3. Using some of your longer scrap resistor leads bent into a U shape, hold the coax into position and slide the jumpers through the provided mounting holes. These jumpers can be soldered on the bottom side of the board to hold the coax into position for final soldering. 4. Solder the coax center conductor to the circuit board, then apply a small fillet of solder to the braid. DO NOT USE TOO MUCH HEAT WHEN ATTACHING THE BRAID, as this can cause the center insulation of the cable to melt. FINAL ANTENNA AND SWITCHER ASSEMBLY Locate the antennas and their hardware. Now we get to put together the antennas themselves. To create the necessary holes for both the mounting screw as well as the cable inputs, take your soldering iron and melt a half moon shape in the side of the lid to allow clearance of the coaxial cable. 1] Use the following picture as a guide to construct the antenna. Place the screw up through the bottom of the antenna PC board, then screw the nut down from the top to hold it in place. Slide one of the internal tooth washers over the screw and place the whip antenna onto that, screwing it down tightly. Once all of the hardware is securely attached, you may install the adhesive backed magnet Material to your home brew antenna. The magnet will hang over the circuit board slightly but do not trim off the excess. The magnets will stay in place more securely if you leave the excess in place. Now were in business!

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ms (8 kHz). Use a frequency counter to verify the clock frequency is 8 kHz +/- 250 Hz if you desire. Getting the clock frequency to exactly 8 kHz is not necessary for proper operation, however, the values of R27 and R28 can be changed to adjust the clock frequency. Verify that closing switch S2 disables the clock. Open S2 (scan stop) and verify the operation of BCD counter U7 by connecting the oscilloscope sequentially to pins 14,13,12, and 11. The signal frequency on these outputs should be approximately 4, 2, 1 and 0.5 kHz, respectively. Verify the presence of a square wave signal on pins 2,4,6 and 8 of buffer U12. Signal Level Indicators The following test uses an audio signal generator to simulate the presence of the Doppler tone. Disconnect the speaker from audio level control potentiometer R50 to prevent loading the signal generator. Connect an audio signal generator to the receiver audio input terminal. Set the generator to apply a 500 Hz sine wave with amplitude 1V P-P. Rotate R50 until the audio overload LED D3 illuminates. Then, adjust R50 until low signal level LED D4 lights. Adjust R50 so that LEDs D3 and D4 are off, set calibrate control R36 to the center of its range and adjust damping control R19 for minimum damping (fully CCW).

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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. The audio generator must be capable of very fine frequency adjustment in order to observe the transition. All LEDs in the display may appear to be on if the signal generator frequency is just 10Hz different from that of the antenna rotation frequency determined by U4. It is interesting to observe the sharpness of the digital filter on pin 1 of U2 on the oscilloscope as the display makes the transition from counterclockwise. You can see the simulated Doppler tone of the generator come out of the noise, peak and return into the noise as the transition takes place. Calibration Control Verify the function of the calibrate control by adjusting the audio generator equal to the antenna rotation frequency. At this point, only a single LED will illuminate. Rotate the calibrate control through out its range and observe the direction indicating LED "move" around the display. The range of movement should be more than 360 degrees. The direction indicating LED may move slightly if the generator frequency drifts. It is very difficult to keep the generator frequency synchronized exactly, but that's not necessary in this test. Disconnect the signal generator and reconnect the speaker to the receiver audio input terminal. Antenna Switcher Verifying proper operation of the antenna switcher sequencing circuit requires only a DC voltmeter. Connect the antenna switcher to the Doppler RDF unit and position the four mag-mount antennas on a table. Do not install any of the whip antennas for this test. It is essential that the antenna be turned on in sequence to emulate an antenna spinning in a circular pattern for the Doppler RDF unit to operate correctly. A single antenna turned on out of sequence is enough to produce a bogus RDF reading. It does not matter if the antenna spins clockwise or counterclockwise.

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also work well. As a safety measure, secure each PopTop Mag-Mount with 20 pound fishing line when operating the vehicle at highway speeds. Attach all four whip antennas to the mag-mount antenna bases placed about the center of the car top. Connect the RF output of the antenna switcher to a FM receiver transceiver tuned to a strong NOAA weather broadcast signal. Caution: Again, make sure you disable transmit mode if you are using a transceiver! It is best to use a smaller, handheld walkie talkie with your DDF1. The unit connects easily to the antenna on your handheld and because they have less output power, there is less chance of doing damage by accidentally transmitting into your DDF1. Adjust the receiver's audio to a comfortable level in the external speaker. Apply 12 V to the RDF unit and spin the antenna by closing switch S2. As soon as S2 is closed, you should hear a 500 Hz tone imposed on the receiver audio. Rotate audio level adjust control R50 so that low signal level LED D4 and audio overload LED D3 are extinguished. Never trust bearing indications if D3 and/or D4 are illuminated. The direction indicating display should be relatively constant with a single LED lit, or one or two adjacent LEDs alternately illuminating. Adjust calibrate control R36 so that the direction indicating LED is consistent with the general direction of the NOAA transmission with respect to your location and the position of the car. Have the driver slowly circle while you observe the display. You should see the direction indicating LED move in the opposite direction as the car is turning in a circle. The position changes relative to the changing direction of the car, however, the direction indicated from the center of the circle the car is driving should remain fixed. If the display turns in the same direction as the car, flip phase invert switch S3 to the opposite position to correct the 180 degrees phasing offset. This completes the rough calibration procedure. Final Calibration A more accurate calibration can be achieved while the car is in motion. Position a volunteer with an HT 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. The display should change to 180 degrees indicating the signal is coming from directly behind the car as the vehicle passes the transmitter. The moving calibration producer functions to average out false reflected signals caused by multipath propagation. You may notice that the Doppler tone changes as the car moves about. The Doppler tone will sound like a pure, undistorted 500 Hz sine wave in the absence of reflected or multipath interference. Direction indications are most reliable under these conditions. When reflected or multipath signals are present, the Doppler tone will sound raspy and distorted.

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Those signal components may arrive from different directions causing false bearing indications. The LED display tends to jump around randomly under these conditions. Avoid taking bearing information when the Doppler tone sounds raspy. You can minimize display jitter by slowing the response time of the digital filter. This is accomplished by increasing damping control R19. With a little time, you can master the art of Doppler RDFing. The wide bandwidth antenna switcher can be used for DFing on other bands, provided the proper antenna whip lengths and antenna spacing are used. Arrange the antennas in a square pattern. Typical antenna spacing for common frequencies is shown in the table below. Whip lengths are measured from the top surface of the mag-mount PC board base to the tip of the antennas.
Frequency 146 MHz 223 MHz
Antenna length in inches 1/2
446 MHz 7 7/8 You can determine the correct antenna length for other frequencies by interpolation of values from the table above. The Doppler DFer will work on virtually any VHF/UHF frequency! FINAL CASE UP When all your tests are complete, you will want to case up your main PC board. First, attach the overlay to the plastic case front. The best (only) way to do this is to spray the surface with a light coating of window cleaner. Next, peel the backing from the overlay and position it so that all the holes line up. At that point, smooth down the overlay with your fingers and leave the case top with the overlay properly positioned until the window cleaner evaporates. If you try to place the sticker on a dry surface and do not place it correctly the first time, you will be unable to remove the overlay without ruining it. Once the overlay is dry, you can attach the board to the case using the screws provided. While youre waiting you can attach the speaker to the case bottom using the screws included in your kit. The speaker fits over the holes drilled into the plastic case bottom. Insert the two screws into the holes in the case bottom and then place the speaker mounting holes through the screws. A nut on each screw will hold the speaker tight to the case bottom. Plug the

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speaker into the 2 pin header and align the case top and bottom. Put a few more screws in place and youre ready to roll. TROUBLESHOOTING INSTRUCTIONS While we had hoped that it wouldnt come to this, if you are having trouble with your direction finder, here are a few suggestions. Use a methodical, logical troubleshooting technique. Most problems can be solved using common sense. A volt-ohm meter and a clear head are usually all that are needed to correct any problem. Most problems are due to misplaced parts and/or bad solder connections. Working backwards through the assembly steps will often lead you to the problem. Please understand that it is nearly impossible to troubleshoot by phone, any specific questions should be documented and sent to us by mail. 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 Inc. Attn. Hobby Kit Department 793 Canning Parkway Victor, NY 14564 And once again, thanks from the folks at Ramsey!

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Doppler Radio Direction Finder Quick Reference Page Guide Introduction to the DDF1. 4 DDF1 Circuit Description.. 4 Parts List..11 DDF1 Assembly Steps.14 Component Layout..17 Schematic Diagram..18 Initial Testing..22 Ramsey Warranty..23
REQUIRED TOOLS Soldering Iron (WLC100) Thin Rosin Core Solder (RTS12) Needle Nose Pliers (MPP4 or RTS05) Small Diagonal Cutters (RTS04) ADDITIONAL SUGGESTED ITEMS Helping Hands Holder for PC Board/Parts (HH3) Technicians Tool Kit (TK405) Desoldering Braid (RTS08)
Price: $5.00 Ramsey Publication No. MDDF1 Instruction manual for: RAMSEY MODEL NO. DDF1 DOPPLER RADIO DIRECTION FINDER

DDF1 36

FM100B 6

frequency while also helping you to determine if you have L1 adjusted properly! Normally if the PLL is locked and L1 is tuned properly, we know what the control voltage will be to achieve the requested frequency by characterizing the PLL loop voltage versus frequency. If we had requested 108.0 MHz, we know the PLL control voltage should be around 8.9 VDC to be locked. If it is not within that range, the locked LED will not light on the display. What are all those additional parts in the VCO for? These allow our composite stereo or mono signal from pin 5 of U2 to be placed on our carrier signal (the frequency you selected). By adding an extra variable capacitor D2 (another varactor diode) along with C9 into the VCO circuitry, the composite signal is fed in to the VCO at a specific level after dividing it by R6 and R7. As the audio swings positive and negative, the frequency goes up and down at the same rate the audio does. This is in turn called frequency modulation (FM) due to the frequency shifting back and forth with reference to your audio signal! In order to get our locked signal out over the air we have to boost the output of our VCO a bit. To do this we use a fancy new part we call the GAL5. This is actually a very well-matched (RF-wise) amplifier with several transistors inside that give us plenty of RF gain without unwanted signals being added in. It by itself has enough gain to give us our 25 mW output (R3 turned fully CW for full output). It also provides plenty of level for some further amplification with the export model (FM100BEX). Because our amplifier is not truly linear, it introduces some harmonics. Harmonics are multiples of the primary frequency. The primary one we are trying to get rid of is the second harmonic (F x 2) which in our case winds up in the aircraft band. It is extremely important for us not to interfere with ANY other transmissions in ANY band. The best filter for the job is the low-pass filter consisting of L3, C63, C59, C67, L4, C64, L5, and C68. This has an upper cutoff frequency at 110 MHz to prevent anything above from getting out onto the antenna and over the air. U2 (the BA1415 FM stereo transmitter IC) is what does all the work of creating your stereo subcarrier as well doctoring your audio signals for transmission. This new version of stereo modulator chip (the old one was a BA1404) has some impressive capabilities and fantastic sound as compared to the older versions. For one it contains a limiter to prevent over-modulation, as well as the pre-emphasis circuitry and some low pass filtering on the audio. It is basically an entire professional transmitter on a chip! All of the required low-pass audio filtering we wanted could not be performed within the chip so we added some more external filtering to give it an even better, richer sound. Now that we are done with the RF section, lets look into the audio circuitry starting at the inputs and going forward to U2. We are going to take a closer look at the microphone amplifier, audio mixer, audio switcher, and peak hold meters to find out the purpose of each. For ease of description we will only

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consider the Right channel due to the Left channel being practically identical. Right off you will see we have two sets of RCA input jacks for the two channels of audio we are able to mix together. This audio passes right through the front level controls so that we can control the audio level for proper mixing and distortion-free sound. U5:A is the right-channel audio summing amplifier. It takes Line 1 and adds it to Line 2 giving you an amplified output on U5:A pin 1. This summed or mixed output then goes through R52 before encountering Q7. Q7 acts like an open switch when its off or a closed switch shorting out the audio to ground (so it doesnt go beyond this point) when its on. Q7 is controlled by a combination of U1 (the microcontroller) and U13 (the AGC amplifier for the microphone). U1 enables or disables the Auto AGC feature of the FM100B. The Auto ACG feature works by U12 detecting a level of audio from the microphone, and if loud enough, U13, set up as a level detector, mutes the audio coming in by turning on Q7 and Q8. We will get back to the microphone circuit in a minute. If the AGC circuit is off, audio continues to U5:D (another summing amplifier). This stage sums the audio from the microphone circuit and the audio from our current line input signal together. The level of microphone audio mixed in is controlled by R16. Notice that there is another transistor (Q2) on the microphone line. This works just like Q7 and allows U1 to mute the microphone signal when necessary. Once mixed, the sum of the audio from the two RCA jacks and the microphone audio enters the low-pass filter. Filtration is provided by a complex mix of two low-pass notches and a regular low-pass filter to achieve a steep cutoff frequency. A notch at 19 kHz prevents any higher frequency audio components from interfering with our stereo multiplexing signals. If you look at the schematic you will see a section boxed off to indicate where these filters are located. You can see there are quite a few parts involved! The components were chosen to keep a nice bright sound as well as maintaining good stereo separation. I wont

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list the part numbers here since they are easy to spot in the boxed off area. The graph shows the low-pass response of the audio filter. You can clearly see the two notches that combine together to give a nice sharp low pass response. Part of the output of U4:D (the output of the low pass filter) is monitored by the level indicators. IC U7:B, D5, R71 and C69 comprise a peak hold detector. Part U7:B and D10 make up a real diode, meaning there is no.7 volt drop that is normally associated with a diode. Because the diode is accounted for in the feedback of the opamp its forward voltage drop is nullified. The real diode will charge C69 quickly on positive going signals without discharging it on the negative swings. The discharge cycle (or rate) is left solely up to R71. The larger the value, the longer the time the peak hold function is. The voltage on the peak hold is then observed by using an LM3915 bargraph display driver (U9) and a ten segment LED bargraph. This part is pretty self explanatory, its really just a voltage meter with a log scale instead of a linear one. The rest of the audio from U4:D enters U2 (the stereo modulator IC) and is converted to RF for transmission. This audio can also be monitored on J6s RCA audio monitor output which is at line level by this point. You can use a tape recorder on these or a headphone amplifier to hear what you are transmitting before it goes out over the air! Now we can go back to the microphone amplifier. U12 is a microphone conditioner IC. It has a feature that we use in the FM100B that really help us out by eliminating a lot of manual work. This is the AGC or Automatic Gain Control. This prevents us from overloading the audio circuitry when we get excited and yell into the microphone. When the amplitude of the signal coming from the microphone increases, the gain of the microphone amp decreases to keep its output relatively the same over varying input levels. U13 is the voice detection IC. Voice detection is used to make the Auto AGC feature of the FM100B. Essentially pin 7 of U13 goes high when there is a varying signal level seen on the microphone (as compared to the constant level of background noise). When pin 7 goes high, it turns JFETS Q7 and Q8 on making them act like voltage controlled pots. The more they are turned on, the less resistance is seen from source to drain. This has the effect of muting the audio from the line level inputs and allowing only the microphone to be heard when there is an active voice signal detected. U1 (the microcontroller) has the ability to override this feature by turning on transistor Q5 and pulling the gate inputs of Q7 and Q8 low. This prevents them from turning on no matter what the output of U3 tries to do. The microcontroller can also mute the microphone audio by setting the MIC_MUTE line high. This turns on Q2 and grounds out all the microphone audio. R30 and C25 smooth out the switching transitions so that there is very little popping heard like is apparent in most switches. This MUTE line is also used to turn on the microphone line when the speaker sounds a tone to prevent it from being

FM100B 9

transmitted over the air. The whole process of filtering, mixing, and level detecting is repeated in the left channel as well. This completes the basic analog circuit description of the FM100B. If you are interested in more detail of how it works, there are many good books and magazines which deal with circuitry of this sort in smaller manageable circuits which can help you delve further in what is going on. MICROCONTOLLER DESCRIPTION The coding of the microcontroller is mostly set up to simply process the changing of the frequency and monitoring the VCO voltage. As you will see, the codes logistics lay out in an easy to follow pattern. Lets look at a sample code operation. We will start with two given conditions: - The unit is powered up - The unit has been set in setup mode. In this state the far right decimal point is blinking and your frequency may be changed. 1. A user presses the FREQ UP button. 2. The microcontroller stops scanning the LD (Lock Detect) line and sees what key the user has pressed. 3. Its a Frequency key? Is the unit in setup mode? 4. Yes. Increase the frequency value in RAM by 100 KHz. 5. Send the appropriate divide by N to U2 along with the rest of the required data. 6. Decode the display digits and update the display for the new frequency. 7. Mute the microphone. 8. Send a confirmation beep to the user. 9. Un-mute the microphone. 10. Wait for key release (if no key release, repeat process from step 4). 11. Continue polling LD and updating status indicators. We hope all of this information will help you better understand about what is going on inside the FM100B. This should give you some insight if for some reason you have assembly troubles or something isnt working properly when you finish building the unit. Remember most projects like this are made up of many smaller ones. All you have to do is break them down to understand them better. Now on to building!!!

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RAMSEY LEARN-AS-YOU-BUILD ASSEMBLY STRATEGY Be sure to read through all of the steps, and check the boxes as you go to be sure you didn't miss any important steps. Although you may be in a hurry to see results, before you switch on the power check all wiring and capacitors for proper orientation. Also check the board for any possible solder shorts, and/or cold solder joints. All of these mistakes could have detrimental effects on your kit - not to mention your ego! Kit building tips: Use a good soldering technique - let your soldering iron tip gently heat the traces to which you are soldering, heating both wires and pads simultaneously. Apply the solder on the iron and the pad when the pad is hot enough to melt the solder. The finished joint should look like a drop of water on paper, somewhat soaked in. Mount all electrical parts on the top side of the board provided. The top side is clearly marked with the word TOP, you cant miss it. This is the side that has little or no traces on it, but is covered with mostly copper. When parts are installed, the part is placed flat to the board, and the leads are bent on the backside of the board to prevent the part from falling out before soldering (1). The part is then soldered securely to the board (2-4), and the remaining lead length is then clipped off (5). Notice how the solder joint looks on close up, clean and smooth with no holes or sharp points (6).

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Since this is a professional transmitter, we sincerely hope you put this together in a professional manner. This project will not work as well as you wished if you just slap it together without following good assembly techniques and follow all instructions. No matter how clear we may think our manual is, if you have any questions give us a call at the factory. We will be happy to help you with any problems you may run into. This is a mixed signal project meaning there is digital, audio, and RF circuitry all in one unit. As with all RF circuitry, we want to mount the parts AS LOW AS POSSIBLE to the board. A 1/4 lead length on a resistor not mounted close to the board can act as an inductor or an antenna causing all sorts of problems in your circuit. Be aware though that there are stand up components in your circuit. They dont need to be squished to the board. Keep the portion of the resistor closest to the board mounted right on the board.
For each part, our word "Install" always means these steps: FM100B ASSEMBLY 1. Pick the correct part value to start with. 2. Insert it into the correct PC board location. Make sure the part is mounted flush to the PC board unless otherwise noted. 3. Orient it correctly. Follow the PC board drawing and the written directions for all parts - especially when there's a right way and a wrong way to solder it in. (Diode bands, electrolytic capacitor polarity, transistor shapes, dotted or notched ends of IC's, and so forth.) 4. Solder all connections unless directed otherwise. Use enough heat and solder flow for clean, shiny, completed connections.
Lets begin by sorting out our components and cross-checking them against the parts list to make sure we have received everything.
IMPORTANT NOTE! The surface mount parts in your FM100B have been preinstalled for you. Please do not call the factory for your missing parts; simply turn the board over and youll find them soldered into place.

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FM100B PARTS LIST Semiconductors 2 MV2105 Varactor Diodes (In TO-92 case, 2 pins) (D1,2) 4 2N3904 NPN General purpose transistors (Q1,3,4,5) 3 BS170 JFET Transistors (Q2,7,8) 5 1N4148 Switching Diodes (orange glass body, black stripe) (D3,4,5,6,9) +5V Voltage Regulator (VR1) 1 MC68HRC908JK1CP Microcontroller with sticker on top (U1) 1 BH1415F Stereo Modulator IC Pre-installed! (U2) 3 LF347N Quad Opamps (U4,5,8) 1 GAL5 Pre-installed! (U6) 1 LM358 Dual Opamp (U7) 2 LM3915 Semi-log bargraph drivers (U9,10) 1 MM5451 Serial Shift Register LED driver (U11) 1 SSM2165-1S Microphone conditioner (U12) 1 LMC662CN CMOS Dual operational amplifier (U13) Resistors (5% - fourth band is gold, only listed in Section D) ohm resistor (brown-black-black) (R12) ohm resistors (brown-black-brown) (R26, R99) ohm large 1 Watt resistor (brown-red-brown) (R58) 11 1K ohm resistors (brown-black-red) (R15,17,20,34,38,53,62,80,88,96,97) 5 4.7K ohm resistors (yellow-violet-red) (R22,28,33,39,41) 25 10K ohm resistors (brown-black-orange) (R1,2,3,4,7,9,13,19,27, 35,48,49,52,54,57,59,67,70,78,79,81,84,85,94,111) 2 18K ohm resistors (brown-gray-orange) (R63,89) 7 22K ohm resistors (red-red-orange) (R5,21,43,51,69,73,98) 1 27K ohm resistor (red-violet-orange) (R112) 2 12K ohm resistor (brown-red-orange) (R6,113) 2 39K ohm resistors (orange-white-orange) (R61,87) 8 47K ohm resistors (yellow-violet-orange) (R14,30,37,40,71,90,91,110) 4 100K ohm resistors (brown-black-yellow) (R10,18,68,95) 1 220K ohm resistors (red-red-yellow) (R11) 1 470K ohm resistor (yellow-violet-yellow) (R23) Resistors (1% - fifth band is brown, only used in Section D) 2 3.32K ohm resistors (orange-orange-red-brown) (R66,93) 4 10.0K ohm resistors (brown-black-black-red) (R55,56,82,83) 2 51.1K ohm resistors (green-brown-brown-red) (R65,92) 2 61.9K ohm resistors (blue-brown-white-red) (R60,86) 4 82.5K ohm resistors (gray-red-green-red) (R46,47,76,77) 4 121K ohm resistors (brown-red-brown-orange) (R44,45,74,75)

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10A. Install DISP4, the other 10 segment bargraph display. Make sure to align this in the same way as before and solder all 20 pins. 11A. Install DISP1, one of the two digit displays. Notice how there is no indication of pin 1 on these. You want to orient the display so that the lettering on the one side faces towards U11. It should be positioned so that the Decimal Point is closest to U11. Solder all 18 pins. 12A. Install DISP2, the other two digit display. Again orient the lettering towards U11 before soldering all 18 pins.

1/4"

S ame height as D S 1+D S 2
13A. Install D7, one of the small red LEDs. Notice that if you look straight at the LED there is a flat side. This indicates the Cathode side of the LED. The Cathode side is also indicated by the shorter of the two leads. Make sure to install the flat side or the shorter lead in the same way as shown in your diagram. They only light up if they are installed correctly. Before soldering though, this and the next LED are the only parts that we do not mount flush to the PC board. In this case we want to mount them so the lens of the LED is at the same height as DISP1 and DISP2. These LEDs will eventually be lining up with holes in the front panel. Once the height is set, bend the leads to hold the LED in place, then solder. (Note: Some builders prefer to temporarily install the front panel on the case and line up D7 and D8 flush with the front panel overlay. This increases the viewing angle of the indicator when it is tight to the display.) 14A. Install D8 in the same fashion, making sure it is at the same height and orientation as in the previous step. Now would be a good time to check all of your solder connections for opens and bridges on the back side of the board. The next few steps will be to install the components that are mounted on the rear side of the front panel (two jumper headers and two electrolytic capacitors). These parts are shown in light gray instead of black on the Display Board Parts Layout Diagram. 15A. Install J11, a five pin jumper block (shorter leads soldered onto the board). Again make sure you are putting them on the opposite side of the board from where the rest of the parts have been located. This jack is where the numeric display gets its power and the data for display values. 16A. Install J10, another five pin jumper block. This is where the power for the bargraphs is applied and the signal levels for the bargraphs are sent for display (mount it on the backside like J11).

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C. AUDIO MIXER While it is not completely seen, the audio mixer also involves some of the microphone section we just completed. This mixer section consists of out two pairs of summing amplifiers, and some of the Auto AGC circuit. We will hold off on the two big dual pots until later so do not install these in this section. 1C. Install R88, a 1K ohm resistor (brown-black-red). 2C. Install R73, a 22K ohm resistor (red-red-orange). 3C. Install R79, a 10K ohm resistor (brown-black-orange). 4C. Install R80, a 1K ohm resistor (brown-black-red). 5C. Install R70, a 10K ohm resistor (brown-black-orange). 6C. Install R69, a 22K ohm resistor (red-red-orange). 7C. Install R48, a 10K ohm resistor (brown-black-orange). 8C. Install R51, a 22K ohm resistor (red-red-orange). 9C. Install R53, a 1K ohm resistor (brown-black-red). 10C. Install R52, a 10K ohm resistor (brown-black-orange). 11C. Install R43, a 22K ohm resistor (red-red-orange). 12C. Install R62, a 1K ohm resistor (brown-black-red). 13C. Install R78, a 10K ohm resistor (brown-black-orange). Note this resistor is mounted in a stand-up fashion.

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14C. Install R85, a 10K ohm resistor (brown-black-orange). 15C. Install R59, a 10K ohm resistor (brown-black-orange). 16C. Install R49, a 10K ohm resistor (brown-black-orange). 17C. Install U5, one of the LF347 quad low noise opamps. Make sure the dot or tab indicating pin 1 is installed in the same orientation as the tab shown on the Parts Layout Diagram. Solder all 14 pins after making sure each pin has been inserted into the board. 18C. Install Q7, a BS170 FET. Make sure the flat side of the transistor is in the same orientation as shown on the Parts Layout Diagram. 19C. Install Q8, another BS170 FET. Again check orientation. Note that these are the transistors that can mute the audio when the Auto AGC function is enabled. 20C. Install R90, a 47K ohm resistor (yellow-violet-orange). R90 sets the recovery time for the audio to resume after an Auto AGC function. If you wish to customize the recovery time, lower this value to speed it up or raise it to slow it down. It is located way over on the right hand side of the board. Its time to take an eyeball break before we move on to the next section of our project! Not including the pots that will be used for control, the mixer and microphone sections are now complete. This would be a good time to go through and check your work for good assembly practice. Check for solder bridges, cold solder joints, and improperly oriented devices. A common practice among engineers and techs here at the factory when you cant find a mistake is to get up, take a short break and come back with a new perspective. You would be surprised how many problems you can find when you do this. Onward!

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D. LOW PASS AUDIO FILTERS Note that we will be installing all of our precision parts in these next few steps. The 5% and 1% components are listed together so follow the steps closely! 1% values are used so the filters are well matched on the Left and Right channels (these have 5 bands). 1D. Locate the center of the board where this group of parts is to go. We will begin on the left side of this area. 2D. Install R76, an 82.5K ohm 1% resistor (gray-red-green-red-brown). 3D. Install R95, a 100K ohm 5% resistor (brown-black-yellow-gold). 4D. Install R81, a 10K ohm 5% resistor (brown-black-orange-gold). 5D. Install R77, an 82.5K ohm 1% resistor (gray-red-green-red-brown). 6D. Install R89, an 18K ohm 5% resistor (brown-gray-orange-gold). 7D. Install R84, a 10K ohm 5% resistor (brown-black-orange-gold). 8D. Install R82, a 10.0K ohm 1% resistor (brown-black-black-red-brown). 9D. Install R93, a 3.32K ohm 1% resistor (orange-orange-red-brown-brown). 10D. Install R83, a 10.0K ohm 1% resistor (brown-black-black-red-brown). 11D. Install R87, a 39K ohm 5% resistor (orange-white-orange-gold). 12D. Install R94, a 10K ohm 5% resistor (brown-black-orange-gold). 13D. Install R75, a 121K ohm 1% resistor (brown-red-brown-orange-brown). 14D. Install R92, a 51.1K ohm 1% resistor (green-brown-brown-red-brown).

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DISPLAY SCHEMATIC

FM100B 27

15D. Install R74, a 121K ohm 1% resistor (brown-red-brown-orange-brown). 16D. Install R86, a 61.9K ohm 1% resistor (blue-brown-white-red-brown). 17D. Install C76, a 68 pF 5% ceramic capacitor (marked 68). All ceramic capacitors in this section are the small yellow 5% type that dont look like a disk. Use an eye loupe to carefully read the numbers on their side before installing them; the 5% body styles all look alike! 18D. Install C70, a 68 pF 5% ceramic capacitor (marked 68). 19D. Install C73, a 680 pF 5% ceramic capacitor (marked 681). 20D. Install C78, a 0.0022 uF 5% ceramic capacitor (marked 222). 21D. Install C75, an 82 pF 5% ceramic capacitor (marked 82). 22D. Install C74, a 56 pF 5% ceramic capacitor (marked 56). 23D. Install C80, a 180 pF 5% ceramic capacitor (marked 181). 24D. Install C79, a 22 pF 5% ceramic capacitor (marked 22). 25D. Install U8, one of the LF347N quad opamps. This IC handles the filtering for the Left channel audio with these surrounding parts. Make sure all 14 pins are through the board before soldering (Its easy to accidentally fold over a pin while installing it). 26D. Install R46, an 82.5K ohm 1% resistor (gray-red-green-red-brown). 27D. Install R68, a 100K ohm 5% resistor (brown-black-yellow-gold). 28D. Install R54, a 10K ohm 5% resistor (brown-black-orange-gold). 29D. Install R47, an 82.5K ohm 1% resistor (gray-red-green-red-brown). 30D. Install R63, an 18K ohm 5% resistor (brown-gray-orange-gold). 31D. Install R57, a 10K ohm 5% resistor (brown-black-orange-gold). 32D. Install R55, a 10.0K ohm 1% resistor (brown-black-black-red-brown). 33D. Install R65, a 51.1K ohm 1% resistor (green-brown-brown-red-brown). 34D. Install R66, a 3.32K ohm 1% resistor (orange-orange-red-brownbrown). 35D. Install R56, a 10.0K ohm 1% resistor (brown-black-black-red-brown). 36D. Install R61, a 39K ohm 5% resistor (orange-white-orange-gold). 37D. Install R67, a 10K ohm 5% resistor (brown-black-orange-gold).

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38D. Install R45, a 121K ohm 1% resistor (brown-red-brown-orange-brown). 39D. Install R44, a 121K ohm 1% resistor (brown-red-brown-orange-brown). 40D. Install R60, a 61.9K ohm 1% resistor (blue-brown-white-red-brown) 41D. Install C57, a 68 pF 5% ceramic capacitor (marked 68). 42D. Install C47, another 68 pF 5% ceramic capacitor (marked 68). 43D. Install C54, a 680 pF 5% ceramic capacitor (marked 681). 44D. Install C60, a 0.0022 uF 5% ceramic capacitor (marked 222). 45D. Install C56, an 82 pF 5% ceramic capacitor (marked 82). 46D. Install C61, a 22 pF 5% ceramic capacitor (marked 22). 47D. Install C62, a 180 pF 5% ceramic capacitor (marked 181). 48D. Install C55, a 56 pF 5% ceramic capacitor (marked 56). 49D. Install U4, another LF347N opamp. This opamp and the surrounding parts handles the Right channel audio filtering. Check all 14 pins before soldering. 50D. Install C52, a 10 uF electrolytic capacitor. Check orientation before soldering as these are polarity sensitive! 51D. Install C48, another 10 uF electrolytic capacitor. 52D. Install C72, yet another 10 uF electrolytic capacitor. 53D. Install C53, one more 10 uF electrolytic capacitor. Check your work up to this point to be sure you didnt make a mistake. It is much easier to check your work in small manageable groups than all at once. Again check for solder bridges and cold solder joints. Especially check around the pins of the ICs for solder bridges since it is a common occurrence.

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E. BARGRAPH PEAK HOLD In this section we will be installing the parts that monitor the peak audio levels and holds them for a long enough period so that we can see the value on the meters (this section is located toward the back of the board). We will also be installing a few capacitors that are actually part of the mixer section (for convenience we decided to install them here). 1E. Install R91, a 47K ohm resistor (yellow-violet-orange). 2E. Install R71, another 47K ohm resistor (yellow-violet-orange). 3E. Install D6, a 1N4148 type diode (orange glass body with black stripe on one end). Make sure this diode is installed in the correct way with the stripe on the same end as shown in the Parts Layout Diagram. This diode and its surrounding circuitry rectifies the audio signal into a DC level. Capacitor C81 then holds this level for a long duration. The resistance of R91 then determines how long C81 holds its charge (the less the value the less time C81 holds the charge). This is seen on the bargraph meters when you have a single pulse like a drum beat. 4E. Install D5, another 1N4148 type diode (orange glass body with black stripe on one end). Again check orientation before soldering. This is the rectifier for the other channel. 5E. Install U7, a LM358 opamp. Make sure to orient it in the same direction as shown in the Parts Layout Diagram. Check all 8 pins to be sure they are through the board before soldering any of them! 6E. Install C81, a 10 uF electrolytic capacitor. Check polarity!

FM100B 30

7E. Install C69, a 10 uF electrolytic capacitor. 8E. Install C83, a 10 uF electrolytic capacitor. Dont get confused the closely spaced + marks on the board for C72, 82, and 83. All three should face the same direction. 9E. Install C82, a 10 uF electrolytic capacitor. 10E. Install J8, a 5 pin jumper header. Make sure and leave the longer leads facing up, with the shorter ends soldered to the board. This is where the connection is made to the front panel. 11E. Install C51, a 10 uF electrolytic capacitor. 12E. Install C58, another 10 uF electrolytic, remember to check polarities! 13E. Install C71, a 10 uF electrolytic capacitor. 14E. Install C77, the last 10 uF electrolytic capacitor in this section. Well thats it for the peak hold circuits and the 15 KHz low pass filter. Quick and painless, wasnt it? We have to go back now and check all our work to make sure that we didnt install anything in the wrong way or have any soldering errors such as bridges and cold solder joints. When youre done, go grab a soda (preferably caffeinated) and give yourself another eyeball break! Our next section is the toughest of the whole kit so make sure you have all of your skills primed and ready for the true test!

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F. TRANSMITTER This is where we definitely want to have clean soldering skills and proper mechanical mounting of parts. If you need a review, shoot back to the start of the manual in the STRATEGY section for tips, especially for surface mount assembly. Make sure all your parts are flush to the board and not waving in the breeze. You will not only lose performance if parts arent installed correctly, but your kit may not work at all! Have patience and follow all directions and you should have no trouble at all. 1F. Install R33, a 4.7K ohm resistor (yellow-violet-red). 2F. Install R28, a 4.7K ohm resistor (yellow-violet-red). 3F. Install R41, a 4.7K ohm resistor (yellow-violet-red). 4F. Install R39, a 4.7K ohm resistor (yellow-violet-red). 5F. Install C29, a 10 uF electrolytic capacitor (orientation, dont forget!) 6F. Install C35, a 10 uF electrolytic capacitor. 7F. Install C21, a 33 pF ceramic disk capacitor (marked 33). 8F. Install C27, another 33 pF ceramic capacitor (marked 33). 9F. Install C38, a 150 pF ceramic capacitor (marked 151). 10F. Install C37, a 0.0033 uF ceramic capacitor (marked 332). 11F. Install C33, a 150 pF ceramic capacitor (marked 151). 12F. Install C32, another 0.0033 uF ceramic capacitor (marked 332).

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13F. Install R6, a 12K ohm stand-up resistor (brown-red-orange). 14F. Install R21, a 22K ohm stand-up resistor (red-red-orange). 15F. Install C7, a 10 pF ceramic capacitor (marked 10). 16F. Install C36, a 0.001 uF ceramic capacitor (marked 102). 17F. Install X2, the 7.6 MHz crystal. This is the crystal which generates the reference frequency for our transmissions. 18F. Install C15, a 10 uF electrolytic capacitor. Again check orientation! 19F. Install C39, a 10 uF electrolytic capacitor. 20F. Install Q3, a 2N3904 NPN transistor. Pay close attention to where the flat side is pointing upon installation. 21F. Install Q4, another 2N3904 NPN transistor. If you look closely at the schematic for this section you will see these two transistors form what is called a Darlington Pair. This gives us the current gain we need for the phase locked loop to work properly. Note the flat side in the opposite direction from Q3. 22F.Install R37, a 47K ohm resistor (yellow-violet-orange). 23F. Install R40, a 47K ohm resistor (yellow-violet-orange). 24F. Install C42, a 0.1 uF ceramic capacitor (marked 104). 25F. Install R26, a 100 ohm stand-up resistor (brown-black-brown). 26F. Install R22, a 4.7K ohm resistor (yellow-violet-red). 27F. Install R7, a 10K ohm resistor (brown-black-orange). 28F. Install C23, a 0.047 uF ceramic capacitor (marked 473 or.047). 29F. Install R27, a 10K ohm stand-up resistor (brown-black-orange). 30F. Install R18, a 100K ohm stand-up resistor (brown-black-yellow). 31F. Install C28, a 47 uF electrolytic capacitor. Again note orientation. 32F. Install C18, a 10 uF electrolytic capacitor. Orientation. 33F. Install C8, a 0.001 uF ceramic capacitor (marked 102). 34F. Install D1, one of the MV2105 varactor diodes. These look a lot like transistors because they are in TO-92 type cases, but they only have two leads. This makes it easy to orient them properly to the flat side as shown in the board layout. D1 is the primary tuning diode.

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35F. Install D2, the other MV2105 varactor diode. Again note orientation. This diode provides our modulation. 36F. Install C9, a 10 pF ceramic capacitor (marked 10). 37F. Install R9, a 10K ohm stand-up resistor (brown-black-orange). 38F. Install R23, a 470K ohm stand-up resistor (yellow-violet-yellow). 39F. Install C30, a 0.001 uF ceramic capacitor (marked 102). 40F. Install R14, a 47K ohm stand-up resistor (yellow-violet-orange). 41F. Install C11, a 0.1 uF ceramic capacitor (marked 104). 42F. Install R10, a 100K ohm resistor (brown-black-yellow). 43F. Install R11, a 220K ohm stand-up resistor (red-red-yellow). 44F. Install C3, a 10 uF electrolytic capacitor. The + sign indicates the positive lead and the negative lead is marked by a stripe or a band on the part itself. The positive lead (it is also the longer of the two) should be placed in the hole marked with the + sign. Proper orientation of this part will ensure proper operation of your VCO and therefore your whole kit. 45F. Install R36, a 1K ohm trimmer potentiometer. The top is orange and marked 102. This pot is used to adjust your RF level to minimum requirements to prevent interference. 46F. Install C43, a 0.001 uF ceramic capacitor (marked 102). 47F. Install L1, the large metal can inductor with the tunable slug. Make sure the pins are through the holes before soldering into place. Whew! That was a lot of steps. Definitely check all of your work up to this point for orientation mistakes. Double check all of your electrolytic capacitors to be sure the positive symbols are on the opposite side of the negative stripe. Also make sure there are no solder bridges or cold solder joints. Lastly check your surface mount components with an eye loupe or magnifier to see if there are any solder blobs where there shouldnt be. If there are no problems up to this point it is time to move on! Now we are on to easier stuff with less steps. Be careful with your assembly, you wouldnt want to get this far and then make a mistake causing the project not to work. With soldering iron in hand, on to the next section!

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MAIN BOARD PARTS LAYOUT

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G. TRANSMITTER AMPLIFIER This section covers the transmitter section of the standard FM100B. If you purchased the High Power version, you will be installing the added components right after these steps before you move on to the Microcontroller section. U6 has already been installed for you. 1G. Install C88, 0.01 uF capacitor (marked.01, 103 or 10nF). 2G. Install D9, IN4148 glass diode. Be sure to match the band on the diode with the polarity band on the PC board. 3G. Install L7, 2.2 uH inductor (looks like a fat resistor with red-red-goldsilver bands). 4G. Install R99, 100 ohm resistor (brown-black-brown). 5G. Install C89, 2.2 pF (marked 2.2). 6G. Install C49, a 0.01 uF ceramic capacitor (marked 103). 7G. Install R58, a 120 ohm large 1 Watt resistor (brown-red-brown). This resistor will run a bit hot but dont worry; this is normal and well within the ratings of the component. Place the component in the holes in a stand-up fashion to increase the parts heat dissipation abilities. The body of the part should be closest to U6 and off the circuit board by about 1/16 to avoid physical contact with the amplifier. 8G. Install C50, a 0.1 uF ceramic capacitor (marked 104). 9G. Install C65, a 0.001 uF ceramic capacitor (marked 102). 10G. Install C66, a 4.7 pF or 5 pF ceramic capacitor (marked 4.7 or 5). 11G. Install L3, one of the pre-wound 4 turn inductors.

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12G. Install C63, a 39 pF ceramic capacitor (marked 39). 13G. Install C59, a 0.001 uF ceramic capacitor (marked 102). 14G. Install C67, a 27 pF ceramic capacitor (marked 27). 15G. Install L4, a 4 turn pre-wound inductor. 16G. Install C64, a 75 pF ceramic capacitor (marked 75). 17G. Install L5, the last of the 4 turn pre-wound inductors. 18G. Install C68, a 47 pF ceramic capacitor (marked 47). 19G. Install C44, a 0.01 uF ceramic capacitor (marked 103). 20G. Install C46, a 0.001 uF ceramic capacitor (marked 102). 21G. Install C45, a 100 uF electrolytic capacitor. Pay very close attention to the orientation of this large capacitor, it must be installed correctly! 22G. Install L8, 13 turn air core inductor. 23G. Install the whip antenna with the provided screw (Std. version only). 24G. Solder the whip antenna screw in place on the bottom side of the board. This may take a bit of time due to the heat that must be transferred from your soldering iron to the large metal area you are working on. This will allow you to remove the antenna at a later time while keeping the mounting screw captured (Std. version only). 25G. Remove the whip antenna until the later casing instructions (be careful, its hot!). Jump to the High Power Manual (FM100BEX) if you have purchased that version. Install the High power parts before moving on to Section H.

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H. MICROCONTROLLER Although the microcontroller interconnects and controls the entire circuit. This section deals with the parts which are fairly exclusive to the controller itself. Well wait until later to install the switches because they get in the way while were installing the rest of the parts. Note that components C6, R8, and X1 are not installed (these holes are provided for future use only if needed should a different microcontroller be used). The current version of U1 does not require or operate with these three parts installed so leave these positions open. 1H. Install C17, a 0.1 uF ceramic capacitor (marked 104). 2H Install R5, a 22K ohm resistor (red-red-orange). 3H. Install C4, a 10 pF ceramic capacitor (marked 10). 4H. Install C12, a 0.001 uF ceramic capacitor (marked 102). 5H. Install C5, a 0.01 uF ceramic capacitor (marked 103). 6H. Install R17, a 1K ohm stand-up resistor (brown-black-red). 7H. Install Q1, a 2N3904 NPN transistor. Note the flat side for installation. 8H. Install R4, a 10K ohm resistor (brown-black-orange). 9H. Install C10, a 0.1 uF ceramic capacitor (marked 104). 10H. Install R12, a 10 ohm resistor (brown-black-black). 11H. Install SP1, the mini speaker. Make sure the + terminal (labeled on

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the bottom side of the speaker) is facing towards C10 and away from Q1. This is where confirming tones are sounded when a button is depressed. 12H. Install R1, a 10K ohm resistor (brown-black-orange). 13H. Install R2, a 10K ohm resistor (brown-black-orange). 14H. Install R3, a 10K ohm resistor (brown-black-orange). 15H. Install J4, a 5-pin connector. Solder the short end to the board. This is where the display power and signals are sent for the front panel. 16H. Install the 20 pin IC socket for U1. If the socket has a notch in one end, install it in the same position as shown on the Parts Layout Diagram to prevent confusion later. 17H. Install U1, the IC with the sticker labeled FM100B into the socket. Find the dot or notch on one end of the chip and orient it as shown in the Parts Layout Diagram. If your chip has a large 1 on one end (signifying pin 1), this end is oriented as though it were a notch. It should be placed at the end of the socket closest to R17. This is the brains of your unit that keeps track of all the button presses, the frequency lock, and the rest of the circuitry. Be sure all 20 pins are firmly in the socket and none are bent under. Take another break and check all of your work for soldering and part installations for possible problems before we move on to the Jacks and Switches.

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15K. Plug in the AC Input Molex plug onto the Molex strip labeled J2. The locking header holds it snugly in place. 16K. Take the other end of the coax that you soldered to the board in step 14K and connect the BNC connector to the BNC barrel you placed on the rear panel in step 13K. That takes care of that! Were almost ready to plug it in the wall and give her a run. But first we want to check everything we have done up to this point very closely. Especially the circuitry involved with the line voltage connections. Check and double check your wiring against that shown in the diagram and pictures. Also make sure that the two high voltage connections are to either side of the Molex plug and not in the center. The green wire of the line cord is Earth ground, not a high voltage connector. It can be connected to either of the center pins of J2. Be very careful around these connections. When we plug it in they will always be live! Especially be careful of the power switch S1. The top pins on the switch are connected directly to the ones mounted in the PC board so line voltage (117 VAC) will be present on those as well! When you have completely finished the unit and its up and running, you may want to coat these connections with nonconductive 100% silicone (such as tub sealant). Be careful to not get it inside the switch movement however or you wont have a good switch any longer!

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L. PC BOARD MOUNTING In order to test the unit it is much easier to have the PC boards mounted in the case assembly. This keeps down the possibility of wires crossing or metal objects shorting out across the back of the PC board (not to mention the live AC circuitry). MAIN BOARD MOUNTING 1L. Mount the main board to the bottom of the case making sure the holes line up with the standoffs in the bottom. Note that you will be installing 5 board screws; the screw under the power switch is not used. 2L. Using the shorter pre-made 5 wire jumper cable, connect from J4 to J11. Make sure pin 1 of J4 is connected to pin 1 of J11 (J11 pin 1 is closest to DISP1). Verify your orientation of the connectors by looking at the mark you made previously indicating pin one. 3L. Using the other pre-made 5 wire jumper cable, connect from J8 to J10. Again make sure that pin 1 of J8 is connected to pin 1 of J10 (J10 pin 1 is the top pin closest to R96). 4L. Connect the 4 pin Molex connector from the rear panel to J2 on the main board. You can then set the cover in place without having to screw it down until your initial tests are made. FRONT PANEL MOUNTING 5L. Align the front panel display PC board with the holes in the front panel assembly. 6L. Check the LEDs for proper installation height and positioning. If they are misaligned, now is a good time to correct that. 7L. Using 3 of the #4-40x1/4 screws, mount the board securely to the front panel. 8L. Admire your work up to this point. (WOW!)