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Ramsey Electronics FX Series Manual

220 mhz amateur pll synthesized fm transceiver 220 - 240
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220 MHZ AMATEUR PLL
SYNTHESIZED FM
TRANSCEIVER 220 - 240
Ramsey Electronics Model No.
•
Synthesized - no crystals to buy !
•
Perky 5 watt RF output
•
Dual conversion sensitive receiver with crystal and ceramic IF filters
•
PACKET ready ! Dedicated packet interface connector on back!
•
12 Channels, expandable to as many as you want - programmed with
diodes !
•
Easy 4 evening assembly - need only a voltmeter and another rig for
testing
•
Fantastic manual teaches as you build, rig is assembled in bite-sized
sections that are tested as you build - your kit will work first time !
•
Rig operate over 20 MHz of band, great for snooping out of band !
Published in Three Sections:
•
FX-series General Reference Information
•
Kit Assembly Phase I: Circuit Stages A through F
•
Kit Assembly Phase II: Circuit Stages G through TX
Plus:
•
Fold-out Schematic Diagram
FX-223

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Summary of Contents for Ramsey Electronics FX Series

  • Page 1 220 MHZ AMATEUR PLL SYNTHESIZED FM TRANSCEIVER 220 - 240 Ramsey Electronics Model No. FX-223 • Synthesized - no crystals to buy ! • Perky 5 watt RF output • Dual conversion sensitive receiver with crystal and ceramic IF filters •...
  • Page 2 Ramsey Publication No. M223FX First Printing: December, 1991 Copyright 1991,1994 by Ramsey Electronics, Inc. All Rights Reserved. Revision number 2.0 Published by Ramsey Electronics, Inc. Printed in the United States of America RAMSEY ELECTRONICS, INC. Amateur Radio and Hobby Kits Dept.

  • Page 3: Table Of Contents

    Basics of Externally-Controlled Frequency Switching ......38 FX-series GLOSSARY of Terms ............40 Troubleshooting Guide ..............46 Note on Replacement Parts..............49 RAMSEY ELECTRONICS FX Kit Warranty Terms ......51 FX-223 Master Component Index ............53 KIT ASSEMBLY: PHASE 1 Assembly and Explanation of Circuit Stages A through F (including Kit Parts List, kit-building tips and preliminary receiver &...
  • Page 4 FCC regulations ENFORCE severe penalties for unlicensed operation of radio transmitting equipment and for interference with other communications services, whether malicious or accidental. Ramsey Electronics, Inc. sells the FX-223 transceiver solely for correctly-licensed operation. It is the sole responsibility of builders and operators of this RF electronics device, capable of emissions controlled by FCC Rules, to understand and comply with those rules.
  • Page 5 SPECIFICATIONS FOR THE RAMSEY FX-223 General: Frequency Range: Any 20 MHz segment between 220 and 240 Tuning: Diode-programmable PLL synthesis 12 front panel selected frequency pairs, easily expandable by switches, microprocessors, computers, etc. Programming: 5 KHz steps with programmable offsets Transmit Offset: Programmable: Simplex, +1.6, -1.6, Aux Mode:...
  • Page 6 INTRODUCTION to FX-series VHF Transceiver Kit Assembly For the 1990's, Ramsey Electronics has adopted a "Learn As You Build" philosophy for ALL our electronics kits. We feel that licensed ham operators should know about the equipment they use, and also should have the desire to understand how their gear works.
  • Page 7 parts as a finished product! For a minimal investment of your time as well as your well-earned money, you will have a VHF FM voice-data transceiver that you will truly own. Real "owning" ultimately means knowing how to maintain and understand something that we have, in contrast to merely possessing a thing because you spent the bucks to do so.

  • Page 8: A Message To Ham Radio Beginners

    A MESSAGE TO HAM RADIO BEGINNERS: If you have just earned your Novice or Technician license, or are studying for either of them right now, we'd like to say a special Thank You for choosing this Ramsey VHF/UHF transceiver as part of your ham radio beginnings. We have tried to make this instruction manual as clear as possible.

  • Page 9: Dc Power Supply Considerations

    DC POWER SUPPLY CONSIDERATIONS : Your Ramsey FM Transceiver is designed to operate from any stable DC voltage source in the 12 to 15 volt range, from typical car, boat or plane 12V systems to a wide variety of battery packs or AC-powered DC sources. In a pinch, you can get on the air for quite a while with 8 to 10 ordinary "D"...

  • Page 10: Enclosure And Hardware Considerations

    Are we trying to discourage you? No, not really! We know you can see that there are good reasons to consider calling Ramsey Electronics and getting your CFX case on its way while you work on the PC-board and PLL Programming.
  • Page 11 Quantity RS Part No. Description 1992 Price ($) 270-272/74 Deluxe Project Enclosure 8.79 or 10.79 1 set 274-section Pkg. of 3 or 4 knobs 2.00-3.00 1 set 270-201 Rub-on project labels 2.99 2 sets 276-195 PC-board standoffs/ 2.38 This $16 to $18 (plus tax) in basic hardware also presumes availability of all needed drill bits and/or a reamer or punches of sufficient size to make the needed access holes for the rear panel jacks.

  • Page 12: Ramsey Cfx Transceiver Enclosure Kit

    THE RAMSEY CFX TRANSCEIVER ENCLOSURE KIT: The CFX Kit is very obviously a fair value and solid investment for the long term performance and worth of your transceiver. As we have mentioned, we make it "optional" ONLY because some of our ham customers have specialized applications requiring only the basic PC board kit.
  • Page 13 resoldered after passing through the grommet. Snap in the locking section of the relief grommet only AFTER both the red and black wires are in place. 4. Remove the two screws from the SO-239 antenna connector, gently bend the lugs as needed to match the rear panel holes, then secure the jack and lugs to the rear panel.

  • Page 14: Guide To Pc-Board I/O Connections

    GUIDE TO PC BOARD I/O CONNECTIONS: In addition to primary interconnections required for jacks and controls, etc., your FX-series Transceiver PC board provides additional access to operating voltages and circuit features to make later customizing as neat and easy as possible. All these points are plainly marked on the board itself and highlighted on the facing page, with a few other components for...
  • Page 15 1. PRIMARY CONNECTIONS: PWR (near L20): +12-15 volts DC from S1. GROUND: - DC from battery or power supply. SPEAKER: both connections near U6 and U2. MIKE: both connections (IN & GND) near notched end of U1. SQUELCH: three connections near L1. VOLUME: three connections near VR1 and C42.

  • Page 16: Microphone & Speaker Information

    MICROPHONE & SPEAKER INFORMATION The FX transceivers with the hardware supplied are designed to accept standard ICOM or ICOM-compatible speaker-mikes such as MFJ-284. The most conveniently available such unit is Radio Shack No.19-310. Be aware that the receiver audio amplifier is capable of supplying a husky 2 watts or more of audio power and will drive full-size communications speakers to excellent volume levels.

  • Page 17: Vhf Packet Data Operation

    VHF PACKET DATA OPERATION Your FM transceiver was planned and designed to accommodate easy and reliable VHF packet radio operation. The J1 Packet I/O port can be quickly connected to many modern TNC's and the Ramsey P-IBM or P64 Packet Modems with Radio Shack's shielded DIN cable (42-2151).
  • Page 18 RAMSEY FX-SERIES FM TRANSCEIVER (With emphasis on the PLL and VCO) MC13135...

  • Page 19: Circuit Overview

    FX-223 CIRCUIT OVERVIEW The FX-223 VHF FM Transceiver circuit theory is explained in progressive stages and in some detail as part of our "Learn As You Build" approach to electronic kits. Builders are encouraged to study and learn about a stage or section, build it and then test it before going to the next stage.
  • Page 21 Stage CR: Integrated FM Receiver The MC13135 is a complete FM narrowband receiver from antenna input (pin 22) to audio output (pin 17). The low voltage dual conversion design results in low power drain, excellent sensitivity and good image rejection in narrowband voice and data link applications.
  • Page 22 connection as well as +DC, D6 is grounded through RF choke L17, which prevents the antenna RF from being shorted to ground. During Transmit, D7 passes RF from the transmitter to the antenna, and L17 again prevents loss of RF to ground. During transmit, D6 is blocking transmitter RF from the receiver circuit.
  • Page 23 thereby increasing available modulation voltage.
  • Page 24 FREQ. BINARY PROGRAMMING VALUES 1010 1101 0111 0000 222.000 44,400 1010 1111 1100 1000 225.000 29,600 The VCO requires a very pure source of well-filtered DC, free of AC hum, alternator whine or other disturbance. R19 and the 47 uf C40 form a basic low pass filter.
  • Page 25 on all 16 parallel inputs. Unlike simpler PLL IC's, U6's phase detector has TWO outputs at pins 7 and 8. These outputs go through very simple low pass filters (R44-C68, R53- C91) to cut back the 5 KHz whine sound of U6 at work. Op amp U5:A sums together the phase detector outputs and the output of U5:A is passed through a network of 2.2 uf electrolytic capacitors (C67,70,90,92) to smooth out the phase detector pulses to clean DC for controlling the VCO.
  • Page 26 particular frequency and its "N" number: 1. Descending Subtraction (see Programming Worksheet) 2. Printed reference lists (see Popular 2 Meter Frequency Pairs) 3. Computer programs (see our sample BASIC program) We recommend strongly that you fully understand how to make the calculation yourself, because that is your ONLY means for checking the accuracy of printed information, computer programs or the operation of experimental programming circuits.

  • Page 27: Quick-Reference Programming Guide

    Using the FX-series FM Transceiver Quick Reference Programming Guide: In addition to "pencil & paper math" calculation directions and also a handy computer BASIC program for programming the FX- series Transceiver for any frequency and transmit offset within its specified range, we provide this guide for binary programming of a variety of popular Repeater frequency pairs as well as some other frequencies of general interest.
  • Page 28 FX-223 Quick Program Reference Standard 220 MHz band repeater pairs and selected frequencies Program as follows: 1. Install diodes at 16K, 8K, 4K and NO diodes at 32K, 2K ,1K positions. 2. PLUS install diodes at 512 through 1 positions as needed per this Quick Reference Chart.
  • Page 29 Frequency 512 256 128 64 32 16 8 224.34 44,868 224.36 44,872 224.38 44,876 224.40 44,880 224.42 44,884 224.44 44,888 224.46 44,892 224.48 44,896 224.50 44,900 224.52 44,904 224.54 44,908 224.56 44,912 224.58 44,916 224.60 44,920 224.62 44,924 224.64 44,928 224.66 44,932 224.68...
  • Page 30 Some popular Simplex frequencies Frequency 512 256 128 64 32 16 8 223.42 44,684 223.44 44,688 223.46 44,692 223.48 44,696 223.50 44,700 223.52 44,704 223.54 44,708 223.56 44,712 223.58 44,716 223.60 44,720 223.62 44,724 223.64 44,728 223.66 44,732 223.68 44,736 223.70 44,740 223.72...
  • Page 31 RAMSEY FX-series Programming Worksheet To convert N from decimal to binary, simply TRY to subtract EACH of the 16 binary values from N, always in descending order, always starting with 32768 and always ending with 1. This process will always yield 16 YES or NO answers, which will give you exact diode installation instructions.

  • Page 32: Programming Worksheet

    Using Computer BASIC as a Diode Matrix Programming Aid The purpose of the following BASIC program is to be as CLEAR AND GENERIC as possible with no concern for programming efficiency or sophistication. Those who enjoy and understand programming in Basic can dress it up to suit themselves.
  • Page 33 Sample BASIC Program Listing 50 PRINT “Enter Receiver Frequency as 6 digits with NO decimal!” 52 INPUT “For example: 146520. Enter here: “; F 55 N = F/5 60 PRINT “The FX146 or FX220 N number for binary conversion is “; N 101 AA = 0 102 BB = 0 103 CC = 0...
  • Page 34 320 IF NL => 8 THEN MM = 1 325 IF NL > 8 THEN NM = NL - 8 326 IF NL < 8 THEN NM = NL 330 IF NM => 4 THEN NN = 1 335 IF NM > 4 THEN NX = NM - 4 336 IF NM <...

  • Page 35: How To Activate An Auxiliary (Non-Standard) Offset

    Here’s an example of the screen display for the program as written, showing the results for an entry of “146865” and ready for the next frequency to be entered as 6 digits: For example: 146.52 MHz. = 146520. Enter here >>> ? 146865 The FX146 or FX220 N number for binary conversion is: 29373 32768 - 0 16384 - 1...

  • Page 36: Programming "Minus" Offsets

    4. You can connect as many of the channel rows as you wish in this manner, but remember that each would follow the same non-standard split you have programmed. Only one such split can be programmed in the AUX matrix row.
  • Page 37 Then, ADD 1: This is our two's complement value which we program into our offset matrix. You'll see these diodes in the position for -1.6 MHz TX offset. Even though it appears that we are adding a huge N number to the original transmitter frequency, the binary adders will follow the rules of binary addition and provide the proper programming information to the PLL synthesizer.
  • Page 38 Invert all bits: Add 1: Sum at '8' bit position, carry 1 Sum at '16' bit position, carry 1 Sum at '32' bit position, carry 1 Sum at '64' bit position, carry 1 Sum at '128', no carry needed Final result: SWITCHING The 12 front panel switched channels, with never a need for a crystal will cover most applications generously.
  • Page 39 2. Any auxiliary programming device can be wired to a switched position on the FX- transceiver matrix as well as to the auxiliary points illustrated. 3. "SPDT" switching may be devised to select offsets. 4. Programming Shortcuts are possible for ham-band operation. (See text). FX TRANSCEIVER EXTERNAL PROGRAMMING BASICS FX-XCVR RIBBON CABLE 1N914/...
  • Page 40 FX-SERIES TRANSCEIVER GLOSSARY The following is a deliberately INFORMAL collection of: • Technical terms useful to know in understanding your FX- transceiver design. • Acronyms (phrases expressed by first letters of words: example: PLL = Phased Locked Loop) • Selected Electronics Industry "jargon" Any of these words or expressions might be used in this instruction manual or in conversation related to your FX- transceiver, either with other hams or with Ramsey technicians.
  • Page 41 CCW = see CW below. COR = "Carrier Operated Relay," a switching circuit activated by the detection of a carrier signal in a receiving circuit. "CW" = TWO common meanings in electronics: "Continuous Wave" for the communicating of Morse code signals, or "Clockwise" to designate a point on a variable control.
  • Page 42 to RF ground, the horizontal elements are called a "groundplane." HIGH = In solid-state circuitry, to say a given device pin or circuit point is at a "logic high" is to say that it shows a + DC supply voltage at that point. Switching to the opposite state (LOW) or back again for some specific purpose is a fundamental capability of the circuit.
  • Page 43 MUTE = to turn off, to render silent. (See also SQUELCH) N = can be any number to solve in a classroom problem, but "N" is THE magic number (decimal) to understand in FX binary frequency programming. N = the frequency in KHz divided by 5 KHz.
  • Page 44 Since such accessories can use ANY style of plug for either mic or speaker function, Ramsey Electronics has adopted the popular ICOM-compatible standard for the FX transceivers.
  • Page 45 UNLOCK, unlocked = refers to the condition in a PLL (phased locked loop) where one or more elements of the loop become defective or incorrect, preventing the phase detector from supplying the correct control voltage to the oscillator for the intended frequency of operation. VARACTOR = a diode whose capacitance can be varied in step by the amount of DC voltage applied to it.

  • Page 47: Troubleshooting Guide

    the detail of our explanations, be sure you set one channel up for 146.52 FX- TROUBLESHOOTING GUIDE MHz Simplex before you pursue troubleshooting. It is very important to have The FX- transceiver is designed to W-O-R-K with a minimum of adjustment or a clear understanding of how to program the frequency synthesizer and alignment.

  • Page 49: Note On Replacement Parts

    PNP transistors, Zener diodes, switching diodes, voltage regulator (5V), hookup wire, LED, controls, antenna connector, replacement 1-amp fuses. Order from RAMSEY ELECTRONICS: Most RF and VHF transistors, coils, crystals, PIN diodes, varactor diodes, trimmers, filters and most IC chips. U1 and U6 are Motorola devices These parts might be in stock at service shops featuring Motorola equipment.
  • Page 50 D11,D12 6.2 V Zener RS276-561 7808 ECG964, SK3630 or RE 7805 RS276-1770 MC13135 RE or Motorola LM380 ECG740A, SK3328 or RE UPB569 LM324 RS276-1711 LM358 ECG928, SK3691 or RE MC145152 RE or Motorola...
  • Page 51 Very rarely, a sour component might slip through. All our kit parts carry the Ramsey Electronics Warranty that they are free from defects for a full (90) days from the date of purchase. Defective parts will be replaced at our expense. If you suspect a part to be defective, please mail it to our factory for testing and replacement.

  • Page 52: Kit Assembly Phase 1

    KIT ASSEMBLY PHASE 1: Stage A: DC Power Regulation & Distribution Plus Packet Data I/O Connector Stage B: Receiver Audio Amplifier Stage CR: Integrated Circuit FM Receiver Stage DR: Receiver, Tuned RF Input and Preamp Stage E-F: Transceiver VCO with Buffer Stages Each set of Assembly Instructions is introduced by an explanation of how that part of the circuit works and what it is for.
  • Page 53 FX-223 MASTER PARTS LIST Before beginning assembly, take some time to check and organize these kit components in such a way that you can find them easily and not lose any or confuse them. Leave parts supplied on tape strips in the strips until you need them.
  • Page 54 CRYSTALS: 1 10.240 MHz, has 2 leads (Y2, PLL reference frequency) 1 21.855 MHz, has 2 leads (Y1, receiver IF oscillator) 1 21.4 MHz crystal filter, has 3 leads (FL1, 1st IF filter) INDUCTORS: 1 455 KHz shielded inductor, marked LB53303HK (L1) 1 Shielded variable coil, orange bottom (L7) 2 .015 uH, 1.5 turns, .125"...
  • Page 55 1 27 pf (C72) 2 39 pf (C80,C87) 6 100 pf (may be marked 100 or 101)(C17,27,32,35,39,46,50) ADDITIONAL DISC CAPACITORS: 22 .001 uf (may be marked .001, 102 or 1nf) (C1,2,3,4,10,18,23,24,38,44,47,52,57,59,61,62,64,77,83,86,88,89) 15 .01uf (may be marked .01, 103 or 10 nf) (C11,33,36,37,45,53,55,63,68,69,91,97,98,99,103) 10 .1 uf (may be marked .1 or 104) (C5,6,8,9,13,14,41,58,65,85) ELECTROLYTIC (Polarized) CAPACITORS:...
  • Page 56 to 100K) (R7,S1) 1 10K squelch control potentiometer (R13) 1 12-position rotary switch (S2) 1 3.5 mm. jack, miniature (J2, speaker) 1 2.5 mm. jack, subminiature (J4, microphone) 1 5-pin female DIN PC-mount connector (J1, packet) 1 SO-239 coaxial RF connector (J3) 1 28 pin DIP IC socket (for U6) 1 DC power cord with inline fuseholder and 1A fuse 1 1/2"...
  • Page 57 VERY IMPORTANT PC BOARD ASSEMBLY INFORMATION FOR A-L-L OUR BUILDERS! 1. Your FX- transceiver PC board is double-clad with plated-through holes. What this means in practice is that it is VERY important to select and install correct part values the FIRST time around. This type of board makes "desoldering"...
  • Page 58 at the factory have tried to help by grouping similar or related parts in individual sealed bags. Sorting organizers popular among kit builders include empty egg cartons, muffin tins, small box tops, or the corrugated edges of box cartons. Since the assembly of this kit is presented in distinct stages, some builders may prefer to group their parts by stage before beginning assembly.
  • Page 59 21. Use the extra spaces provided throughout this manual to write down the details of any changes or revisions noted on additional sheets that may be supplied with your kit. 22. You will be installing various wires for switches, controls and jacks very early in the assembly procedure.
  • Page 60 STAGE A: DC POWER INPUT REGULATION & DISTRIBUTION and PACKET RADIO I/O CONNECTOR (J1) The "power supply" for your FX- transceiver is, basically, any "12-volt" battery or well designed power supply operating from 120VAC or other source. In theory, all "12V" sources should provide pure DC voltage to your FX- transceiver DC input.
  • Page 61 Stage A DC Power Input, Regulation, and Distribution. Plus, Packet Radio I/O Connector (J1).
  • Page 62 Stage A: ASSEMBLY STEPS A1. Strip 1/8" of insulation from the heavier-gauge black wire, insert and solder in the GROUND hole. This connection may be soldered on the TOP side of the board as well as the solder side. FUSE A2.
  • Page 63 A10. Study the PC board, locate the triangular set of 3 holes for VR2 (type 7805), and insert VR2 so that the flat metal tab side is toward the center of the board. Press VR2 in as far as it will go, solder and trim. A11.
  • Page 64 1000 pf is the same as .001 uf. This notation (102) is similar to the resistor color code to indicate resistance values. A14. Install C3, .001 uf. A15. Install C4, .001 uf. A16. Install C1, .001 uf (Don't confuse with C65). A17.
  • Page 65 Stage B: Receiver Audio Amplifier The secret to the fine performance of the LM380 audio amplifier lies in careful selection and physical positioning of the several external components required to complete its circuit. The LM380 is a self contained general purpose audio amplifier capable of over 2 watts audio output with a voltage gain of 50.
  • Page 66 Stage B: Receiver Audio Amplifier and Speaker Connection...
  • Page 67 Stage B: AUDIO AMPLIFIER CIRCUIT ASSEMBLY: Some of the Stage "A" steps required more detailed explanation than simply inserting and soldering parts. As we move along, there will be more and more short "one liners"! The following steps will complete a working audio amplifier ready to power up and test.
  • Page 68 B13. Use two 8" lengths of hookup wire (or 8" of 2 conductor wire) to prepare the Speaker Cable. Neatly strip and tin all 4 ends as in Step B11. B14. Solder both wires of one end of this speaker cable to the two marked points near C37.
  • Page 69 STAGE CR: FM RECEIVER CIRCUIT DUAL CONVERSION SUPERHET WITH IF FILTERS...
  • Page 70 U1 is minimal in comparison to what was previously required for a quality FM receiver circuit For years, Ramsey Electronics has employed a similar IC, the MC3359 as the heart of our popular FM receivers for the 10, 6, 2 and 1.25 Meter bands. We adopted the MC13135 IC for the FX-series because of its features especially suited for state-of-the-art FM voice and digital communications requirements.
  • Page 71 diminish other signals while boosting signals in the 223 MHz region. 2. The First IF converts the incoming 223.50 MHz signal down to 21.4 MHz. In order to do this job, the IC's 1st IF Mixer needs ANOTHER frequency source to mix with the signal presented by the antenna through the filters and preamps of Stage DR.
  • Page 72 ADDITIONAL RECEIVER IC FUNCTIONS AND FEATURES In addition to audio output at pin 17, a separate high speed data output (up to 35000 baud) is available and may be linked directly to a packet TNC or other data controller using the jumper wire pad provided on the PC board. The MC13135 is capable of detecting true FSK (frequency shift keying) in addition to AFSK.
  • Page 73 Verify that filter FL2 is properly seated and soldered. So far, most disc capacitors installed have been from your endless supply of .1, .01 and .001 capacitors. If you have not done so already, now would be a good time to sort and organize all your "picofarad" capacitors, ranging in value from 2 to 100 pf.
  • Page 74 diode (gray body, black band). Observe correct placement of the banded cathode end. Zener diodes are widely used as voltage regulators. They have the interesting property of keeping a constant voltage across their terminal leads. CR26. Install Q1, NPN type 2N3904. Before soldering, press the transistor as far into its holes as possible, with the flat side oriented as shown in the parts diagram.
  • Page 75 FX SERIES TRANSCEIVER Simplified Receiver Block Diagram ANTENNA PASS FILTER HIGH BAND PASS RECEIVE PASS RECEIVE FILTER PRE-AMP FILTER PRE-AMP FIRST 21.4 MHz FILTER, MIXER AMPLIFIER 21.885 MHz SECOND LOCAL PLL CONTROLLED OSCILLATOR MIXER PROGRAMMED 21.4 MHz LOWER THAN 6 POLE...
  • Page 76 Stage DR: Receiver Tuned RF Input and Preamp...
  • Page 77 Stage DR: Antenna Input and RF Preamplifier The operation of the FM receiver IC was discussed in Stage CR. The purpose of the following circuitry is to minimize the strength of unwanted signals and to boost signals in the 220 - 240 MHz range before they reach the 1st mixer input of U1 (pin 22).
  • Page 78 STAGE DR ASSEMBLY: In keeping with our “learn-as-you-build” kit building philosophy, we will install only the components needed for receiving. Be very attentive to capacitor values (in picofarads) and to coil descriptions throughout this section. DR1. Correctly identify and install PIN diode D6. It is the only BA479 used in the circuit, and its number is stamped plainly on the diode body.
  • Page 79 DR12c. After making sure that the body of Q3 is snugly against the PC board and correctly oriented as shown above, solder and trim all three wires. That's all there is to it! DR13: Install C20, 8.2 pf. (marked 8.2). DR14: Install C30, 22 pf (marked 22).
  • Page 80 Stages E - F: Transceiver VCO (Voltage Controlled Oscillator) and Buffer Stages...
  • Page 81 Stage E-F: The FX Transceiver VCO The VCO (Voltage Controlled Oscillator) provides basic frequency control for both transmit and receive modes. It is essential to understand its function in the transceiver circuit. Q7 is the oscillator transistor and the key VCO components are L7, D3 and D23.
  • Page 82 VCO CIRCUIT SUMMARY: The control voltage for the D3 and D23 varactor diodes is supplied through R47 and R25 by the output of U5:A in the PLL synthesizer circuit. We know already that there must be a 21.4 MHz difference between the receive and transmit frequencies of the VCO.
  • Page 83 Stage E: BASIC VCO ASSEMBLY In this Stage, we will assemble the basic VCO (Voltage Controlled Oscillator) circuit. Understanding the function of this stage is especially important for knowing how the FX transceiver works. E1. Select and install shielded coil L7 (orange bottom). It fits in two different ways, and either way will work.
  • Page 84 E20. Install R35, upright, 100K ohm (brown-black-yellow). R35 is between positions for D5 and C62. Steps E1-E20 are presented as a group primarily as a help in visualizing the location of the VCO on the PC board. You have built up the VCO itself and the capacitance multiplier voltage filter provided by C40, Q4, etc.
  • Page 85 F16. Install C35, 100 pf disc capacitor (marked 100 or 101). C35 couples the VCO buffer to the receiver IC. F17. Solder 1/4" lengths of bare wire (trimmed from resistors or capacitors) in the two test point holes marked TP2 and TP3. Study the following optional test procedure before installing a similar test point at TP1.
  • Page 86 test point. The potentiometer will vary the voltage to D3 and D23, thereby varying the VCO frequency and tuning your receiver. VCO AND RECEIVER TEST PROCEDURE: 1. Make sure work area is tidied up and that the PC board has been checked for stray scraps of wire, etc.
  • Page 87 RAMSEY FX-223 VHF FM TRANSCEIVER KIT ASSEMBLY PHASE 2: • Stage G: Understanding and Building the PLL Frequency Synthesizer • Stage H: Building and Programming the Diode Matrixes • Stage M: Microphone Amplifier and PTT Circuit • Stage "TC": Preparing Transmitter Coils, RF Chokes •...
  • Page 88 Stage G: The PLL Synthesizer: Understanding and Assembly...
  • Page 89 Stage G: The FX- Transceiver PLL Synthesizer A reassuring feature of the FX Transceiver is that if you build it correctly and make just a few adjustments, it will work fine whether you understand how it works or not. For most amateurs and beginners, the functions of the PLL Frequency Synthesizer and VCO will present the greatest challenge to understanding.
  • Page 90 Inserted into this circle is the frequency synthesizer (U6 with U3), which compares the output of the VCO with the output of its own 10.24 MHz. Reference Oscillator (see Y2) and also with the frequency programming which you have set up. After making these comparisons, it gives an instruction to the VCO in the form of a precision voltage applied to the varactor diodes, and the cycle repeats itself at lightning speed.
  • Page 91 soon as both strings are exactly on the same frequency. By tuning the one string to the exact pitch of the other, you have corrected the phasing of the two independent frequency sources. Pilots of multi-engine planes (or boats) make slight RPM adjustments to get all engines in phase. If you have two audio oscillators handy, listen carefully as you adjust both to EXACTLY the same frequency.
  • Page 92 • The Phase Detector (or "phase corrector") which compares the 5 KHz Reference Frequency with the "intended" 5 KHz output of the divide by N counter and sends correcting pulses to the VCO to keep the output of the N divider right at 5 KHz. •...
  • Page 93 Unlike simpler PLL IC's, U6's phase detector has TWO outputs at pins 7 and 8. These outputs go through very simple low pass filters (R44-C68, R53-C91) to cut back the 5 KHz whine sound of U6 at work. Op amp U5:A sums together the phase detector outputs and the output of U5:A is passed through a network of 2.2 uf electrolytic capacitors (C67,70,90,92) to smooth out the phase detector pulses to clean DC for controlling the VCO.
  • Page 94 make mistakes: skipping connections, causing solder bridges, etc. Some builders may prefer to push ahead and do all of the repetitive soldering as a single operation, while others do better work with frequent breaks in the phases that involve repetition of steps. The suggested order of assembly is for the benefit of the latter group.
  • Page 95 G17a. Insert and solder U9 as in step G15a. G18a. Insert and solder U10 as in step G15a. Soldering the remaining pins for U7, U8, U9 and U10 may be done either as a single operation or at any other pace preferred by you to ensure careful work (no missed pins, no solder bridges).
  • Page 96 G36. Similarly, install diode D10, same type as D8. G37. Similarly, install diode D24. G38. If you have not done so already, install the MC145152 PLL IC into the 28 pin DIP socket. Be sure to orient the notched end correctly and that all 28 pins are seated in the socket.
  • Page 97 Stage H: Frequency Programming, Understanding and Building your Diode Matrix...
  • Page 98 Stage H: FREQUENCY PROGRAMMING: Understanding and Building the Diode Matrix The labeling of the 16 parallel programming inputs of U6 should have a familiar ring to anyone with at least some understanding of computer principles, which should include all of us by now. Even though our desired "N"...
  • Page 99 "N" for 223.50 MHz = 223500 ÷ 5 = 44,700 Subtracting from N: Remainders & Doodles Position Can you subtract 32768? 11,932 Can you subtract 16384? Can you subtract 8192? 3,740 Can you subtract 4096? Can you subtract 2048? 1,692 Can you subtract 1024? Can you subtract 512? Can you subtract 256?
  • Page 100 Even though there are 16 matrix positions to program, there are some shortcuts to make your job easier for normal ham band operation. Let's look at the upper and lower band edges for the 220 MHz band: Freq 222.00 44,400 225.00 45,000 223.50...
  • Page 101 Can we subtract 512 from 632? YES (Therefore diode at 512) 668 - 512 = 156 Can we subtract 256 from 156? NO (Therefore NO diode at 256) Can we subtract 128 from 156? YES (Therefore YES diode at 128) Can we subtract 64 from 28? (Therefore NO diode at 64) Can we subtract 32 from 28?
  • Page 102 THE RX/TX OFFSET PROGRAMMING MATRIX Diode placement in this matrix follows the same binary number principles as used for frequency programming. This matrix is connected to the 16 programming inputs of U6 through the four binary adders (U7-U10). Fewer programming positions are provided on the board simply because there is no practical use for extremely large or very tiny frequency offsets.
  • Page 103 receiver or repeater output frequency, simply find the the N number for the offset and program it on the offset matrix. Here's one more example. Let's say we want a + 1 MHz offset. 1 MHz = 1000 KHz. 1000 ÷ 5 = 200 = N Converting to binary: (Obviously 200 is less than all values from 8K through 256, meaning that we need no diodes in those positions.) Can we subtract 128 from 200? YES (Therefore diode at 128)
  • Page 104 H1: R68, 1K (brown-black-red). H2: R69, 1K (brown-black-red). H3: R114, 1K (brown-black-red). H4: R65, 1K (brown-black-red). H5: R67, 10K (brown-black-orange). Install the following diodes, be sure to orient the cathode banded end correctly. (Diodes are type 1N914/1N4148): H6: D19 H7: D15 H8a: D13 H8b: D14 H9: D16...
  • Page 105 H41. Form one diode matrix "bridge" for the RECV row of holes. Using the heavier gauge bare wire in your kit, shape, insert and solder this wire bridge as illustrated. HEIGHT ABOVE BOARD = .25 IN. LENGTH = 2.375 H42a. Select five (5) diodes from the master supply of 1N914 or 1N4148 switching diodes provided with this transceiver kit.
  • Page 106 the primary matrix. If you already have a firm plan for how you wish to program some or all of the channel positions, you can proceed with making the frequency programming lines that you are sure about. If you have little or no sure idea of how you want to set up the channel selector switch, you can build up a simple switching system that will let you try any frequency of your choice.
  • Page 107 In lieu of constructing diode bridges and wiring the channel selector switch, you may elect to build your own switching system, using DIP, slide or toggle switches. Do such projects only after your transceiver is finished and working.
  • Page 108 Channel Switch S2 may be installed at whatever point in the procedure that is most convenient for you. Its purpose is to apply +5V to the desired diode bridge. Connect the desired channel positions on the switch to corresponding matrix channel rows using 2" lengths of hookup wire.
  • Page 109 Stage M: Microphone Amplifier and Push-to-Talk Switching...
  • Page 110 Stage M: Microphone Amplifier and PTT Circuit If you have studied all preceding circuit explanations, you have a good idea of what the Microphone and PTT circuitry is supposed to accomplish. Understanding our design clearly and assembling it correctly will save many headaches and will ensure reliable FX transceiver operation.
  • Page 111 R70 limits the current drawn by D17 to a safe level. This LED usefully assures that the otherwise-silent PTT circuitry is indeed functioning and obviously has nothing to do with the RF output of the transmitter. The PTT circuit may also be activated at pin 3 of the Packet I/O jack. A direct short to ground is not necessary.
  • Page 112 M18. Install Q11, NPN transistor type 2N3904. Be sure to orient flat side as shown. M19. Identify and install R46, the yellow color modulation control trimmer potentiometer. It differs from trimmer capacitors by having three terminals. Simply place it in position and solder all three points. NOTE: The remaining three transistors used in this section are PNP types, 2N3906 or similar, marked 228256.

  • Page 113: Test)

    M36: D22, near VR1, type 1N914 or 1N4148. Orient the banded end correctly. (+8T through R107 and D22 turns on Q6 to mute the audio amp IC during transmit). M37: C62, near R105, .001 uf. M38: Diode D5, near R35, type 1N914 or 1N4148. M39: R31, near D5, 47K (yellow-violet-orange).
  • Page 114 OPTIONAL: Interested builders might wish to verify microphone amplifier operation at PC board point "PL" before proceeding, but such a test is not essential at this point. Simply connect a utility test amp to "PL", press the mike button and talk! Assembly Stage "TC": Transmitter Coil &...
  • Page 115 The legs or leads for inserting L12,13,15,16 and L22 should be 1/4" long. The coil should sit 1/8" maximum above the PC board groundplane. 2.5 TU RN 1.5 TU RN Assembly Stage "TO": Programming Standard Repeater Offsets (- 1.6 and + 1.6 MHz) If you did not go ahead and do so when setting up the PLL Synthesizer for receiver testing in Stage "H", now would be a good time to install the diode programming for the standard transmit offsets.
  • Page 116 Stage TX: Transmitter, Buffer and Final Amplifier...
  • Page 117 Stage TX: Transmitter Buffer, Driver and Final The transmitter section, Q10, Q9 and Q8, is conventional VHF RF circuitry that has proven quite reliable in Ramsey transceivers. Just a few circuit notes are in order. Transistor Q10, the transmit Buffer, amplifies the VCO output from C56 to about 10 milliwatts, quite sufficient for checking modulation and PLL alignment in transmit mode as soon as this stage is built.
  • Page 118 IMPORTANT: DO NOT install any parts near Q8 until after Q8 has been installed in accord with the explicit directions in Step TX2. If you fail to observe this caution, it will be virtually impossible to perform the installation of Q8 correctly. DO NOT INSTALL L9, R32 or L10 UNTIL AFTER ALIGNMENT HAS BEEN COMPLETED.
  • Page 119 easily. E. Solder the other end and touch up the first one if necessary. Identify and install the following components: TX4: C56, 10 pf. TX5: R29, 100 ohms (brown-black-brown). TX6. L11, miniature .33 uh. inductor (small green body, two orange stripes) TX7.
  • Page 120 TRANSCEIVER PLL ALIGNMENT (May also be done before Step TX35) Our goal in this test is to verify speech amplifier operation (U4), actual FM modulation of a low-level RF signal (Q10), and correct operation of the PLL Frequency Synthesizer in Transmit mode. If an antenna is connected for this test, it will affect receiver operation only.
  • Page 121 9. Disconnect power and proceed with completing the transmitter section (Steps TX15, etc.) IMPORTANT: If you do not achieve the test results discussed above, there is no point in doing more work on the transmitter section until the problem is solved.
  • Page 122 TX31: L8, 2.2 uH molded inductor (2 red, 1 gold and 1 black stripe). At this point, every single main PC board component has been installed except for L10, R32 and L9, which apply power to the RF output transistors (driver Q9, final Q8).
  • Page 123 TX37. Install C16, 15 pf. TX38. Install C72, 27 pf. TX39. Install C71, 15 pf. TX40. Install L12, the 2 1/2 turn coil prepared in stage TC. Insertion will require you to spread the windings slightly to fit the holes. When mounting these coils, do not allow the wire spirals to contact the PC board ground plane area under them.
  • Page 124 assembly operation. Use the two screws and four nuts supplied and consult the illustration as needed.
  • Page 125 The flange of the connector sits on the outside of the rear panel. Mount the connector with one set of nuts, then mount the low pass filter PC board using the other two nuts. Solder the connector center pin to the board.
  • Page 126 Other FCC licensing is required for operation of this equipment on frequencies outside the Amateur Band. It is illegal for licensed amateurs or other persons to transmit on frequencies for which they are not properly licensed. RAMSEY ELECTRONICS, INC.

  • Page 127: Technicians Notes

    FX-223 TECHNICIAN’S NOTES Throughout production of the “FX” series transceivers, the technicians here at Ramsey have been speaking with customers, making repairs, experimenting, and compiling notes on the FX-223. These notes, and the circuit overview and theory of operation sections of your FX-223 manual, provide extensive information on the inner workings of the FX-223.
  • Page 128 VCO & PLL Faults: (manual pages 21-24, 82 - 89, 90 - 97) 1. PLL not locking. (L7 will not set correct voltage @ TP1) a. Check for proper programming inputs to U6 (pins 10-25). If incorrect, fault lies between diode matrix and inputs to U6. VOLTAGES ON U6 @ 223.5 MHZ IN RECEIVE/TRANSMIT pin ~ VDC pin ~ VDC...
  • Page 129 Some channels are off frequency by different amounts. (Refer to preliminary check # 5) *Common faults: • Improper diode programming. • Solder shorts between traces. (There’re a lot of traces between U6 and the diode matrix!) Transmit Section Faults: (manual pages 25 - 26, 118 - 123) 1.
  • Page 130 • Improper output power measurement.

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