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.
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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 ................... 18 Enclosure Ideas ...
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.
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 DIP) mixer-product detector-oscillator.
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 Components 1 10.24 MHz Crystal (Y1) 1 10.
3 4 4.
FR146 BLOCK DIAGRAM U1 SA602 MIXER U2, 3359 FR146 • 8
FR146 PARTS LAYOUT DIAGRAM FR146 • 9
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.
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. ❒ 9. Install C4, 56 pF. ❒ 10.
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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. Install C8, .
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.
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.
❒ 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.
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.
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.
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.
FR146 TROUBLESHOOTING HINTS Ramsey FR-series FM receivers are among our most widely-used and popular kits. The circuit itself, assembly and use are "cut-and-dried." If your receiver does not work, there is probably either an error in assembly or a defective part. Following is some help in case you experience difficulty. Problem: Receiver completely "dead"- no sound at all.
hearing about significant performance improvements, we do not recommend casual modification attempts. However, there is one practical customization which could be undertaken by experienced VHF experimenters who wish to take advantage of the NE602's ability to accept a crystal resonator instead of the existing L-C tank circuit. The goal would be a one channel repeater monitor or dedicated packet receiver. Inductor L3 and associated capacitors would be replaced by the appropriate crystal tank components.
The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting the factory. 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 a team of knowledgeable people have field-tested several "copies" of this kit straight from the Ramsey Inventory.
FR146 2 Meter FM Receiver Kit Quick Reference Page Guide Introduction to the FR146............... 4 Circuit Description .......................... 5 Parts List ........................................ 6 Simplified Block Diagram ............... 8 Parts Layout Diagram .................... 9 FR146 Assembly Instructions ........10 Testing and Alignment ...................18 Enclosure Ideas..............................20 Troubleshooting Guide ...................21 Notes for Advanced Users .............
