220 MHZ FM RECEIVER KIT Ramsey Electronics Model No. FR220 Keep an "ear " on the local repeater action from your easy chair with this simple and fun to build FM receiver. Tunes the entire 220 MHz band. Ideal way to "audition" before buying a rig! • Tunes any 5 MHz portion of the 220 to 240 MHz band. • Excellent receiver for new Novice classes! • Excellent performance, less than 1 uV sensitivity. • Tuned input, low noise preamp stage.
PARTIAL LIST OF AVAILABLE KITS RAMSEY TRANSMITTER KITS • FM10A FM Stereo 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 • SS70 Speech Scrambler • TT1 Telephone Recorder • SP1 Speakerphone • MD3 Microwave Motion Detector • TFM3 Tri-Field Meter • LC1 Inductance-Capacitance Meter RA
Ramsey Publication No. MFR220 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR FR220 FM RECEIVER KIT TABLE OF CONTENTS Introduction to the FR220 .............. Circuit Description ......................... Parts List ........................................ Simplified Block Diagram .............. Parts Layout Diagram .................... FR220 Assembly Instructions........ Testing and Alignment ................... Enclosure Ideas ............................. Troubleshooting Guide ..................
INTRODUCTION Because all but the most expensive scanners skip over the 220 MHz band, and most Ham rigs are 144 or 440 MHz, 220 is the long forgotten child. This nifty little receiver will allow you to check out 220 at a very affordable price! When you see how uncrowded the band is, and it's excellent VHF propagation characteristics, we're sure you'll order our 220 MHz transceiver and join in.
BUILDING YOUR FR220 KIT There are just over 200 solder connections on the FR220 printed circuit board. That means your work could be 99% excellent and you could STILL have 2 or 3 cold solder points or solder bridges. Since this circuit is more sophisticated than a direct-conversion HF receiver or a simple transmitter, a beginner or casual amateur could have a harder time tracing a problem due to a poor solder connection.
The MC3359 IC has an internal oscillator controlled by the 10.245 MHz crystal. The 10.245 MHz signal is mixed with the 10.7 MHz input from U1 to convert down to the low IF of 455 KHz. The 455 KHz IF is filtered by FL2 and then amplified by a limiting amplifier in U2. Audio demodulation takes place in the quadrature detector, with L4 adjusting the detector. The audio modulation is detected in U2, and the background noise is used to control the squelch.
Fixed Resistors ❒ 1 2 ohm [red-black-gold] (R22) ❒ 3 270 ohm [red-purple-brown] (R6,9,20) ❒ 1 470 ohm [yellow-purple-brown] (R5) ❒ 2 1K ohm [brown-black-red] (R11,12) ❒ 3 10K ohm [brown-black-orange] (R7,17,19) ❒ 1 18K ohm [brown-gray-orange] (R18) ❒ 1 33K ohm [orange-orange-orange] (R14) ❒ 4 47K ohm [yellow-purple-orange] (R4,8,13,21) ❒ 1 100K ohm [brown-black-yellow] (R16) ❒ 1 470K ohm [yellow-purple-yellow] (R15) ❒ 1 1 megohm [brown-black-green] (R10) Capacitors ❒ 1 2 or 2.2 pf (C2,12) ❒ 4 4.
FR220 BLOCK DIAGRAM U1 SA602 MIXER U2, 3359 FR-220 • 8
FR220 PARTS LAYOUT DIAGRAM FR-220 • 9
NOTE CONCERNING THE AUDIO OUTPUT JACK Your receiver kit is supplied with a standard subminiature 2.5 mm (3/32”) audio jack, which mates with commonly available earphone plugs and adapters available at Radio Shack, such as 274-290 (plug) or 274-327 (adapter for 1/8” mono plug). If you prefer to use another size and style jack, we suggest that you still install the original jack and then wire your own jack in parallel with it rather than rough up the PC board to accommodate your jack.
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.
Also, if you plan to use an enclosure other than the custom Ramsey enclosure and knob kit, you may wish to locate the controls differently than provided by the PC board. In this case, the control lugs are wired to the PC board using your own insulated hookup wire, kept as short as possible for neat installation. FURTHER COMPONENT INSTALLATION All "directions" on the PC board (i.e.: right, left, above, below and so forth) assume orientation of your board as shown in the parts layout diagram.
❒ 16. Install R5, 470 ohms [yellow-violet-brown]. 2. SA602 OSCILLATOR-MIXER and VARACTOR TUNING ❒ 17. Install R6, 270 ohms [red-violet-brown]. ❒ 18. Install C7, a .001 uf bypass capacitor (marked .001 or 102). In installing the SA602 IC, you may wish to use an 8-pin DIP socket rather than soldering the IC directly to the board. Reasons for doing this might include the peace of mind of beginners afraid of damaging the IC, or experienced builders testing the merits of the SA602's cousin, the SE602.
FR-220 • 14
FR-220 • 15
❒ 29. Install varactor diode D1, it has a small black body with white and green bands. The white banded end signifies the cathode side. It is important that you have correctly identified D1 as type BB405 and have not confused it with the common signal diode D2. ❒ 30. Install R8, 47K ohms [yellow-violet-orange]. ❒ 31. Install R9, 270 ohms [red-violet-brown]. ❒ 32. Install C13, .01 uf (marked .01 or 103 or 10nf). ❒ 33. Installation of C14.
3. TRANSISTOR COUPLING & AFC CIRCUITS, VOLUME & SQUELCH CONTROLS ❒ 38. Install Q2, a 2N3904 transistor. Observe correct positioning of the flat side. ❒ 39. Install R13, 47K ohms (yellow-violet-orange). ❒ 40. Install C20, .001 uf (marked .001 or 102). ❒ 41. Install R12, 1K ohms (brown-black-red). ❒ 42. Install Q3, 2N3904 transistor. ❒ 43. Install R10, 1 megohm (brown--black-green). ❒ 44. Install R11, 1K ohms (brown-black-red). ❒ 45. Install R22, 2 ohms (red-black-gold). ❒ 46. Install C29, .
❒ 60. Install C25, .001 uf (marked .001 or 102). ❒ 61. Install C26, .01 uf (marked .01 or 103 or 10nf). ❒ 62. Install L4, the 455 KHz quadrature coil, soldering the two pins and the two mounting tabs. ❒ 63. Install U2, MC3359 IC. As in the case of the SA602 IC, you could choose to install an 18-pin IC socket rather than soldering the IC directly. Re-read the previous discussion of IC sockets offered for the installation of U1.
❒ 76. 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 FR220 FM VHF Receiver for reliable monitoring operation, you will need these basic tools: ❒ 1. A useful 220 MHz 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.
❒ 7. Turn the power ON. ❒ 8. Turn R2 (Volume control) until you hear some noise. ❒ 9. Adjust L4 for maximum noise in the speaker. Further alignment now consists of adjusting the oscillator coil L3 to permit the tuning control (R3) to cover the 5 MHz segment between 222 and 227 MHz of primary interest to you. If you are a beginner with no license or other equipment, any Ham operator with a 220 MHz transceiver should be willing to give you the test signal and extra help that you need.
The small 4 turn coils are stretched or compressed when receiving a weak signal. Typically the coils are spread to about 1/4 inch width. Make this adjustment only when receiving a constant weak signal, this simple "tweak" will significantly perk up your reception! RECEIVER SENSITIVITY Your FM receiver features sensitivity under 1 uv.
(1) We wanted to stretch your battery budget: with the LED drawing about 6 ma, how long will your battery last if you leave your receiver on for a few days, just like we leave our computers and Ham or computer accessories on all the time? (2) We thought you'd have more fun planning and installing your own lamp that glows in the dark! (3) We could not decide which color you would like best! THE RAMSEY ELECTRONICS CASE, KNOB & HARDWARE OPTION Your finished receiver can be installed in a variety of enclosures
FR-6 TROUBLESHOOTING GUIDE The 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 an error in assembly or defective part. Following is some help in case you experience difficulty. Problem: Receiver completely "dead"- no sound at all.
Problem: Squelch does not function Re-check all connections and components associated with pins 10 through 16 of the MC3359. Check polarity of C27 and D2. C27 sets the time constant for the squelch circuit. SOME NOTES FOR ADVANCED USERS Unlike Ramsey HF receivers and transmitters, the FR-series of VHF receivers do not offer much PC board space or real need for customization or other modifications.
for fine tuning purposes only. Try reducing C12 to 1 or 2 pF for starters. Finally, the only pin of the MC3359 not used in our circuit is pin 15, for scan control. Perhaps you will come up with some fascinating idea for it! Again, please be sure that you understand your warranty, and that you understand your receiver and how to keep it working, before attempting any modifications. If you've enjoyed this kit, be sure to check out the entire Ramsey kit line.
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.
FR220 220 MHz FM Receiver Kit Quick Reference Page Guide Introduction to the FR220 .............. Circuit Description.......................... Parts List ........................................ Simplified Block Diagram ............... Parts Layout Diagram .................... FR220 Assembly Instructions ........ Testing and Alignment ................... Enclosure Ideas ............................. Troubleshooting Guide .................. Notes for Advanced Users............. Ramsey Kit Warranty .........
