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2 METER FM
RECEIVER KIT
Ramsey Electronics Model No. FR146
Keep an ear on the local repeater action from your easy chair
with this simple and fun to build FM receiver. Tune the entire 2
Meter band or the VHF high Police and Fire band.
• Tunes any 5 MHz portion of the 136 to 175 MHz band.
• Excellent performance, less than 1 uV sensitivity.
• Tuned input, low noise preamp stage.
• True Dual-conversion superhet design with 2 pole
Ceramic High IF and 6 po
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PARTIAL LIST OF AVAILABLE KITS RAMSEY TRANSMITTER KITS • FM10A FM Stereo Transmitter • FM100B Professional FM Transmitter • FM25B Synthesized FM Stereo Transmitter • AM25 Synthesized AM Transmitter • AM1 AM Transmitter RAMSEY RECEIVER KITS • FR1 FM Broadcast Receiver • AR1 Aircraft Band Receiver • AA7 Active Antenna • SC1 Shortwave Converter RAMSEY HOBBY KITS • SG7 Personal Speed Radar
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Ramsey Publication No. MFR146 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR FR146 2 METER FM RECEIVER KIT TABLE OF CONTENTS Introduction to the FR146 .............. 4 Circuit Description ......................... 5 Parts List ........................................ 6 Simplified Block Diagram .............. 8 Parts Layout Diagram .................... 9 FR146 Assembly Instructions ........ 10 Schematic Diagram ....................... 12 Testing and Alignment ..............
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INTRODUCTION TO THE FR146 FM RECEIVER Most Ramsey kits can be classified as “Skill Level 1”. That means that our kits are intended to be sucessful for first-time kit builders. This FR146 FM Receiver is best regarded as a “Skill Level 2” project (or at least Level 1.46!) and should not be taken lightly, even by experienced, licensed radio amateurs. Still, this step-by-step manual is written with the beginner in mind, because we are well aware of the fascination that Two Meters and its
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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. FR146 CIRCUIT DESCRIPTION VHF signals from the antenna are amplified through the tuned input circuit (L1, C3 and L2,C4) by Q1, a microwave bipolar transistor. Q1's output is fed to the input of the SA602 IC, an efficient single-package (8-pin DI
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PARTS LIST Inductors 2 small 1 1/2 turn coils (L1,L2) 1 slug-tuned 3 1/2 turn coil [orange color] (L3) 1 shielded transformer coil [marked LB 53303] (L4) Semiconductors and IC's 1 2SC2498 or 2SC2570A transistor (Q1) 3 2N3904 transistor (Q2,Q3,Q4) 1 SA602 8-pin IC (U1) 1 MC3359 18-pin FM receiver IC (U2) 1 LM386 8-pin audio amplifier IC (U3) 1 Varactor diode, BB505 [orange body marked BB505] (D1) 1 1N4148 signal diode (D2) Special Com
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3 4.7 or 10 uF electrolytic (C15,30,36) 4 100 to 220 uF electrolytic (C14,32,33,35) Controls and Hardware 1 Printed circuit board 3 10K ohm potentiometer (R1,R2,R3) 1 DPDT push switch (S1) 1 PC mount RCA jack (J1) 1 PC mount subminiature speaker jack (J2) 1 9-volt battery bracket 1 9-volt battery snap-on clip REQUIRED, NOT SUPPLIED 1 9-volt alkaline battery 1 VHF antenna with cable terminated in RCA-style plug or adapter 1 Speake
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FR146 BLOCK DIAGRAM U1 SA602 MIXER U2, 3359 FR146 • 8
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FR146 PARTS LAYOUT DIAGRAM FR146 • 9
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RAMSEY “Learn-As-You-Build” KIT ASSEMBLY: We have a twofold "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. FOR EACH PART, OUR WORD "INSTALL" ALWAYS MEANS THESE STEPS: 1. Pick the CORRECT part value to start with. 2. Insert it
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FURTHER COMPONENT INSTALLATION All "directions" on the PC board (ie: right, left, above, below and so forth) assume orientation of your board as shown in the parts layout diagram. Therefore the rear of the board (connectors) is the lower end, and the front (controls) is the upper end. 1. ANTENNA INPUT AND TUNED RF PREAMPLIFIER ❒ 5. Install C1, 100 pF disc capacitor. ❒ 6. Install C2, 10 pF. ❒ 7. Install C3, 56 pF. ❒ 8. Install L1, one of the small 1 1/2 turn coils. ❒
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FR146 • 12
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FR146 • 13
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dot, or notch. Before soldering, make sure that the IC or socket is perfectly fflat against the top of the PC board. Install U1, the SA602, in accord with the preceding directions. ❒ 19. Install FL1, the ceramic filter. This component looks like a capacitor with 3 leads and may be installed either way. ❒ 20. Install jumper wire JMP4. Use a scrap component lead wire bent like a staple that connects the two PC board holes. Jumpers act as "bridges" over PC board traces underneath. ❒ 21. Ins
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PROGRESS SUMMARY So far, you have wired the tuned input from the antenna, the RF preamplifier, and the SA602 mixer-oscillator, including the varactor tuning circuit. The work you have done has actually formed a simple receiver capable of tuning in VHF signals of all kinds and converting them to a low-level 10.7 MHz output to be amplified by Q2. This is a good time to review the steps completed to this point before proceeding. Due to the many functions of the MC3359 FM receiver IC, furt
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4. MC3359 FM IC and ASSOCIATED COMPONENTS ❒ 55. Install R17, 10K ohms [brown-black-orange] ❒ 56. Install R14, 33K ohms [orange-orange-orange] ❒ 57. Install C24, .001 uF [marked .001, 102, or 1 nF]. ❒ 58. Install C25, .001 uF [marked .001, 102, or 1 nF]. ❒ 59. Install C26, .01 uF [marked .01, 103, 10 nF]. ❒ 60. Install L4, the 455 KHz quadrature coil [marked LB53303], soldering the two pins and the two mounting tabs. ❒ 61. Install MC3359 IC, U2. As in the case of the SA602 IC, you could
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❒ 73. Install R16, 100K ohms [brown-black-yellow]. ❒ 74. Install R15, 470K ohms [yellow-violet-yellow]. 5. FINAL CONNECTIONS: THE LM386 AUDIO IC STAGE You now have a working FM receiver ready for adjustment. The output of the MC3359 FM IC simply needs to be boosted to listening level. A few more connections, and your receiver will be ready for adjustment and testing! Now would be a good time to review some of your previous work and also to make sure you have on hand what you'll need f
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TESTING, ALIGNMENT AND ADJUSTMENT To prepare the FR146 FM VHF Receiver for reliable monitoring operation, you will need these basic tools: ❒ 1. A useful VHF signal source. ❒ 2. Hexagonal, non-metallic coil slug alignment tool for L3. ❒ 3. Small screwdriver to adjust L4. 1. Signal source: This signal can be from your test bench equipment or from a "live" source such as a local repeater. The "live" signals are best for fine-tuning, but they also have that VHF communications character
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Further alignment now consists of adjusting the oscillator coil L3 to permit the tuning control (R1) to cover the 5 MHz. segment between 135 and 175 MHz of primary interest to you. Assuming you wish to adjust for the Two Meter 144-148 MHz Amateur Band, adjust L3 until you hear your intended test signal. If you are a beginner with no license or other equipment, any Ham operator with a 2-meter transceiver should be willing to give you the test signal and extra help that you need. The FR14
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Locating the LED immediately above the on-off switch is logical and ideal. The simplest way to make a good installation is to drill a neat hole just slightly smaller than the diameter of the LED. Then, enlarge the hole a little bit at a time just enough to let the LED be pressed in and held firmly. The resistor may be connected to either the anode or cathode of the LED, but the anode MUST go to + DC, with the cathode connected to the nearest common ground point. If you are wondering why we
