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Ten-Tec SSB-CW-AM Instruction Manual

Microprocessor-controlled,15 memories, dual conversion,tunes 100 khz to 30 mhz
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74477
No. 1254
COMPLETE KIT WITH CASE, HARDWARE
SSB-CW-AM RECEIVER
Microprocessor-controlled,
15 Memories, dual conversion,
tunes 100 kHz to 30 MHz
KIT
by TEN-TEC
INSTRUCTION
MANUAL
America's Best!

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Summary of Contents for Ten-Tec SSB-CW-AM

  • Page 1 74477 No. 1254 COMPLETE KIT WITH CASE, HARDWARE SSB-CW-AM RECEIVER Microprocessor-controlled, 15 Memories, dual conversion, tunes 100 kHz to 30 MHz by TEN-TEC INSTRUCTION MANUAL America’s Best!
  • Page 2 KIT Manual No. 74477 (865) 453-7172 Fax (865) 428-4483 Circuit board and manual Copyright © 2012. All Rights Reserved.

  • Page 3: Table Of Contents

    Table of Contents Section l: GETTING STARTED A. General Introduction to Receiver Design and Features B. About this Manual and T-KIT C. Working with the Kit Parts Before Assembly D. Detailed Kit Parts List 8-13 E. Checklist of supplies and tools needed for assembly F.
  • Page 4 Table of Illustrations, Charts and Diagrams 1 . Getting Started Section 16-18 Selected Component Illustrations 2. Assembly Section Phase 1.0 schematic details Phase 1.0 circuit board illustration Fig. 1.1 : LED alignment Fig. 1.2: Installation of J1 , J2 Fig. 1.3: Encoder wiring Phase 2.0 schematic details Phase 2.0 circuit board illustration Fig.
  • Page 5 A. Introduction to Model 1254 Receiver Features and Design Building one's own receiver from a kit has launched countless thousands of people into communications careers or the hobbies of amateur radio and shortwave listening ("SWLing"). The Model 1254 combines the satisfaction of the kit-building experience with the performance features expected in a modern shortwave receiver.

  • Page 6: Section L: Getting Started

    B. About This Manual and T-KIT This T-KIT Manual has THREE sections: 1. Getting Started (This one, which includes the KIT PARTS information prior to any soldering.) 2. Kit Assembly (Presented in seven step-by-step illustrated "Phases".) 3. Reference Information (Such as operating instructions, circuit description, troubleshooting guide and much more.) We understand you may be anxious to get going! When you are ready to do something instead of read,...

  • Page 7: Working With The Kit Parts Before Assembly

    Electronic kit-building has changed dramatically during the 50 years since TEN-TEC's founder (Al Kahn, K4FW) gave a boxcar loaded with war surplus parts to some friends who started a company which became known as Heathkit , so, the several generations of "the hams at TEN- TEC"...
  • Page 8 4. Check and organize ALL Main Board parts per the Kit parts List before you start soldering. Electronics hobbyists have many different ways of sorting and organizing small parts: standing them on a block of styrofoam or in the holes along the edge of corrugated cardboard, arranging them in an egg carton or muffin tin, or making logical piles in a small tray.
  • Page 9 D. T-KIT Model 1254 Receiver KIT PARTS LIST 1. Check and organize all parts before starting construction. 2. See T-KIT Warranty if you believe any parts are missing. The Warranty explains how to contact us. value, please refer to the Component Reference Index (in "Reference"...

  • Page 10: Getting Started

    B. Main Receiver Circuit Board Parts Fixed Resistors The 3 color bands denote resistance value. The 4th band (gold) denotes 5% tolerance. All resistors are l/4-watt unless specified otherwise. Quantity Schematic Part No. Description and Value JMP1-3, R66 30353 4.7 ohm (yellow-violet- ....
  • Page 11 Disc capacitors cont. Quantity Description and Value Schematic Part No. 23396 23245 23260 23261 Film Capacitors (5% tolerance) Quantity Description and Value Schematic Part No. C89, C90 23286 23338 C10, 12 23291 23340 23330 Other Capacitors Quantity Description and Value Schematic Part No.
  • Page 12 Integrated Circuits Quantity Description and Value Schematic Part No. PIC16C57-XT/P microcontroller IC (pre- 98394-1.0 MC7805CT (or LM340T-5) 5- 25095 U8, U9 25062 MC145170P1 PL 25296 NE612AN (orSA612AN) mixer-oscillator 25319 25336 25341 BA618 LED display driver IC 25400 ..........25356 NJM7801FA voltage regulator IC ..........Mounting hardware for U10 (packed with IC's): Quantity Description and Value...
  • Page 13 Other Components, Board-Mounted Hardware: Quantity Description and Value Schematic Part No. 78138 (U2) 27021 R73, R82 30267 NOTE: (The mounting nuts and washers for the volume and clarifier controls may be pre-attached or included with other hardware.) 30856 48079 Crystal, 44. 48235 48228 48339...
  • Page 14 C. Chassis Parts and 0ther Hardware See Foldout titled "Mechanical Assembly Details" inserted at the end of this section. This drawing will help you identify major mechanical parts. Quantity Description and Value Schematic Part No....93341-1A 93367 93342-CN1A ..93116 93109 93110...
  • Page 15 E. What YOU provide to build and operate this T-KIT Model 1254 Receiver REQUIRED, NOT SUPPIIED 9-volt battery (memory backup) Antenna(s) for bands of interest thin-diameter rosin core solder contact cement (to secure panel jack insert, speaker and logo) RECOMMENDED, NOT SUPPLIED: masking tape (to protect front panel during final assembly) headphones with 1/8"...
  • Page 16 F. Model 1254 Receiver Parts ldentification Notes We rely on you to know already what a resistor, transistor, lC "chip" and other common electronic parts "look like." REMINDER: Both the back and inside front covers of this manual provide some light-hearted help on basic parts identification. Each assembly step provides useful help in identifying any part, whether by shape, color-code, manufacturer's markings, or other description.
  • Page 17 Table 1-C Diode Identification Guide The main board uses eight 1N4148 diodes easily recognized as identical to the four diodes installed on the Display Board. The Zener, and Varactor diodes must be identified exactly. Here's some help: TYPE Body Type/Color Cathode Band 1N4148 (8) Glass, copper-color inside...
  • Page 18 Table 1-E CERAMIC DISC CAPACITORS The vast majority of capacitors in this circuit are the ceramic disc type. Our protocol is to identify those in picofarads up to 99 pF simply as 1 pF or 33 pF, etc. There may be one letter to identify temperature characteristics (e.g. 33J = 33 pF.) exact part marking (101, 102, 103, 151, 181, etc.) minus any letter.

  • Page 19: Building Electronic Kits: The Essentials

    G. Building Electronic Kit Projects: THE ESSENTIALS If you've never built an electronics kit before, you are a GOOD candidate for successful construction of this receiver - because we think you'll rely on this instruction manual very diligently. ("Experienced" builders tend to be more inclined to shortcuts which can lead to mistakes!) Both this manual and the engineering discipline for this receiver were done with YOU very much in mind.
  • Page 20 3. SOLDERING: If you are inexperienced, ask any electronics technician to show you how it's done, then do practice soldering/de-soldering on a junked circuit board before working on your kit. Here's what is important: Keep the soldering iron tip CLEAN, using a damp sponge Let the heated connection itself melt the solder, not the iron tip Use a thin diameter of rosin-core solder Use VERY good lighting;...
  • Page 21 H. Model 1254 SWL Receiver Kit Assembly OVERVIEW You will build the Display Board first and then occasionally plug it into the Main Board for further testing. To get a good fit of the LED's and 3- digit displays, you'll be handling the front panel and display lens - be VERY careful not to touch these with your soldering iron! After finishing PHASE 2.0 (Logic and DC Power Input sections), the powered-up Display Board plugged to the Main Board (via P1, P2) can...

  • Page 22: Phase 1.0 Display Board Assembly

    Model 1254 Receiver Kit Assembly Steps and Illustrations Installing parts on the boards Preview of Display Board Assembly Phase 1.0: Display Board Assembly Sectional Schematic Parts Quick-Reference and Display Board Pictorial Step-by-Step Assembly 6-10 Notes on Main Board Assembly 11-12 Phase 2.0: Logic Section and Display Drivers Sectional Schematic and Circuit Board Pictorial 14-15...
  • Page 23 Before you do ANY soldering, we remind you again to do the following: Check and organize your kit parts in whatever way Is most convenient for you. A special IDENTIFICATION GUIDE is provided after the Parts List. Go through this entire manual: familiarize yourself with its organization and illustrations.
  • Page 24 Model 1254 SWL Receiver PREVIEW of Phase 1.0 Display Board Assembly The Display Board is a useful "warmup" project before getting started on the more complex Main Board. It will be plugged in temporarily for Progress Tests in Phases 2.0 through 5.0 and installed permanently at the end of Phase 6.0.
  • Page 25 1254 Assembly...
  • Page 26 QUICK REFERENCE SUMMARY PHASE 1.0: Display Board Encoder Freq/Memory TUNE 1N4148 pushbutton switch multiplexing diode 1N4148 1N4148 1N4148 Green LED AM mode indicator Green LED SSB mode indicator Green LED FAST tuning mode indicator U1-U6 Display LED frequency display 33 ohm, 1/4watt LED display current limiting 33 ohm, 1/4 watt 33 ohm, 1/4 watt...
  • Page 27 PHASE 1.0 Display Board Assembly All parts used for the Display Board are packed together with the board itself . Except for the common 1N4148 diode, all parts in the Display Board kit bag are unique to this assembly phase, even the resistors! (The display board uses 1/8 watt resistors, while all other resistors are 1/4 watt.) All parts except J1 and J2 are mounted on what we will refer to...
  • Page 28 1-3b. Examine one of the small LEDs and the LED outlines illustrated in Figure 1.1 Notice that the anode and cathode ends of the LED's are clearly silkscreened on the board. The anode is the LONGER of the two LED leads. Figure 1.1 1-4.
  • Page 29 Figure 1.2 IMPORTANT: Examine these sockets and notice the row of openings and tiny metal tabs on one side. These tabs will protrude when the sockets are mated to plugs. Therefore install the sockets with the tab rows facing UP, so there is no chance that extended spring tabs can short against the main board.
  • Page 30 1-26. Install switch SW1 (MODE) per Step 1-25. 1-27. Install switch SW2 (MW) per Step 1-25. 1-28. Install switch SW3 (V/M) per Step 1 -25. 1-29. Install switch SW4 (SPEED) per Step 1-25. IMPORTANT SOLDERING TIP! Examine the Rotary Encoder: regardless of whether the 3 silver terminals appear to you to be tarnished, rub them anyway with a clean pencil eraser.
  • Page 31 1-36. Cut two 1/2" lengths of insulating sleeve and slip one on each of the two switch wires. 1-37. Solder one wire to the center lug of the SPDT switch. 1-38. Solder the other red wire to the bottom switch lug. The bottom lug is identified per mounting done in step 1-34.
  • Page 32 Model 1254 Main Circuit Board Assembly In discussing the Display Board, we referred to the "front" and "back" sides of the board. In the Main Board assembly steps, we will refer to the silkscreened side as the TOP and the solder side as the BOTTOM.
  • Page 33 We suggest inserting 3-5 parts, bending the leads to hold them well, double-check, then solder and trim. In choosing the kit-building experience, we are not trying to outpace the robotic manufacturing processes used at TEN-TEC and worldwide! 1254...
  • Page 34 This space is for your notes Phase 2.0 Assembly begins on page 14 1254 Assembly - 13...
  • Page 35 Phase 2.0 Schematic Diagram Details 1254 Assembly - 14...
  • Page 36 Phase Display Driver, Microprocessor and DC Power Input Circuits PLL synthesizer IC U3 and some of its supporting parts are included, in this phase because its 3.580 MHz reference oscillator also supplies the microprocessor clock signal. 1254 Assembly - 15...
  • Page 37 QUICK REFERENCE SUMMARY Phase 2.0: Frequency Synthesizer and DC Input Filter Cap for display driver 470/16v el. 5-40 pF var. Trimcap for master clock (adjust to 3.58 MHz) Bypass on PLL chip Bypass on PLL chip 33/16v el. 33pF Shunt cap on clock crystal 1/50v el.
  • Page 38 Phase 2.0 Assembly Steps Before You Start: A Quick Reference Summary of the parts used in Phase 2.0 is printed on page 16. It may be used first as a guide to gathering parts for this phase. It is provided as an extra help in double-checking correctness of parts values with brief notes on the function of each part.
  • Page 39 2-13. Install right-angle header P1 per Step 2-12. 2-14. Install right-angle header P2 per Step 2-12. 2-15. Install the 28-pin DIP socket supplied for the U2 PIC microprocessor, with the notched end aligned per the notch outlined on the board. Insert carefully, making sure all pins mate their holes with no pin bent back under the socket.
  • Page 40 2-28. Install JMP1 , a "zero ohm resistor" (one black band.) 2-29. Install JMP2 per step 2-28. 2-30. Install electrolytic capacitor , being sure to insert the longer ( + ) lead as shown on the board. 2-31a. Install electrolytic per Step 2-30.
  • Page 41 2B. DC Power Circuitry The following parts are installed near the left rear of the board. 2-43. Install the two-pin terminal J2 with the vertical locking side toward the back end of the board as outlined and illustrated in Figure 2.2. Figure 2.2 2-44.
  • Page 42 OPTIONAL: For Educators and Experimenters Circuit Stage Demonstrations Each Phase of the receiver construction process adds several related circuit stages. In most cases, these circuit sections are capable of "doing something" of possible interest to you if connected to external test equipment of some kind. For example, you can hear an oscillator signal using another receiver, 0r use a signal generator to hear that an IF section is working.
  • Page 43 Phase 4.0: 455 kHz 2nd IF An RF signal generator tuned to 455 kHz can be coupled to the input of U7 at C40 after completing Phase 4B. A nearby general coverage HF receiver or transceiver can be tuned to 455 kHz to confirm oscillation of ceramic resonator Y2.
  • Page 44 Phase 2.0 Progress Test 2-50. Carefully plug the Display board into the sockets on the solder side of the board. With the display facing you correctly, the solder side of the main board faces up. 2-51. Plug the encoder cable into J4. 2-52.
  • Page 45 At this point, further testing of this circuitry consists simply of just playing with it as much as You care to! For example, you can turn to the Operating Instructions in the Reference Section and try out the [MW] and [V/M] functions. You can use the [MW] (Memory Write) function to store frequencies in memory, but keep in mind that the stored information will be lost when power is turned off, because the...
  • Page 46 This space is for your notes Phase 3.0 Assembly begins on page 26 1254 Assembly - 25...
  • Page 47 Phase 3.0 Schematic Details 1254 Assembly - 26...
  • Page 48 Phase VCO's and PLL Circuit The VCO's (Voltage Controlled Oscillators) will be permanently enclosed in metal shields only after their operation is thoroughly verified in Phase 7.0. Four different transistor types are used in Phase 3.0: be sure to identify them correctly and to orient them as outlined on the board.
  • Page 49 QUICK REFERENCE SUMMARY Phase 3.0: VCO's and PLL Circuit DC block on VCO PLL loop filter PLL active filer VCO bypass cap Supply bypass for Q25 Base bypass for Q25 10/25v el. Supply bypass for Q25 27 pF VCO bypass filter VCO coupling cap to PLL 33 pF VCO lowpass filter...
  • Page 50 Phase 3.0 QUICK REFERENCE SUMMARY, cont. VCO source resistor VCO select Active loop filter emitter VCO pull-up resistor Varactor bias resistor VCO switching VCO switching Supply resistor for Q25 Base bias for Q25 Bias for Q26 Emitter resistor for Q26 Bias resistor for Q26 Varactor bias resistor Charge pump bias...
  • Page 51 Phase 3.0 Assembly This receiver uses two voltage-controlled oscillator (VCO) circuits to cover the total tuning range. We'll begin with VCO-1 which uses adjustable coil L3 to tune the 45-58 MHz 1st LO range. 3A. VCO-1 Components Adjustable coil L3 is marked with a brown paint dot and is the VCO coil with the greater number of windings.
  • Page 52 Install the following resistors: 3-7. Resistor (brown-green-brown). 3-8. Resistor R22, 10K (brown-black-orange). 3-9. Install R11, 47K (yellow-violet-orange). 3-10. Install R25, also 47K. 3-11. Install R27, also 47K. Install the following disc capacitors: 3-12. Capacitor C91,100 pF.(marked 101). 3-13. Capacitor (marked 102). 3-14.
  • Page 53 3-22. Identify and install varactor diode D8, type KV3902 (was BB911A). 3-23. Identify and install PIN diode D4, type 1SS135. Install the following resistors: 3-24. Resistor (brown-green-brown). 3-25. Resistor R24, 47K (yellow-violet-orange). 3-26. Resistor R26, also 47K. 3-27. Resistor R37, also 47K. Install the following disc capacitors: 3-28.
  • Page 54 1/4-watt resistors, cont. 3-48. Resistor R18, 4.7K (yellow-violet-red). 3-49. Resistor R19, also 4.7K. 3-50a. Resistor R29, 10K, (brown-black-orange). 3-50b. Resistor R30, also 10K. 3-51. Resistor R32, also 10K. 3-52. Resistor R38, also 10K. 3-53. Resistor R15, 15K, (brown-green-orange). 3-54. Resistor R23, 22K (red-red-orange). 3-55.
  • Page 55 which you will connect your voltmeter to do the L2 and L3 VCO coil adjustments. lf more convenient for your test leads, you can also solder a length of insulated hookup wire instead, and trim it shorter after completing the adjustment. 3-75.
  • Page 56 3-84. Tune from 13.235 MHz to 13.240 MHz. You will likely observe a sharp downward shift in DC voltage at the VCO Test Point, indicating that VCO-2 has been switched in. 3-85. Adjust VCO-2 coil L2 as needed for a DC voltmeter reading of 2.5 volts at 13.240 MHz.
  • Page 57 Phase 4.0 Schematic Details 1254 Assembly - 36...
  • Page 58 Phase Audio Section, AGC, 455 kHz 2nd IF After part 4A this phase is completed, we can test for audio output and proper operation of the volume control. When this phase is completed, the receiver also can detect a 455 kHz signal such as from its 2nd mixer (Phase 5.0) in either AM or SSB mode.
  • Page 59 Phase 4.0 QUICK-REFERENCE SUMMARY Before You Start: The following Quick Reference Summary of the parts used in Phase 4.0 may be used first as a guide to gathering parts for this phase. lt is provided as an extra help in double-checking correctness of parts values with brief notes on the function of each part.
  • Page 60 Phase 4.0 Quick Reference, cont. 1.0K AM detector emitter resistor 2.2K AGC discharging resistor 1.0 M AGC time constant 220K AGC charging resistor AGC rectifier pull-down AGC input resistor 4.7K IF amp input load 1.0K AM detector emitter resistor Forward bias for AM detector 2.2K IF amp output load, U8 1.0K...
  • Page 61 Phase 4.0 Assembly Steps Section 4A. Audio Amplifier Circuit U6 is a self-contained audio amplifier SIP (single inline pin) IC, using only a volume control and a very few resistors and capacitors to complete a 1.5 watt audio amplifier. We will assemble this circuitry plus the speaker/headphone connections now, then test their functioning, to confirm audio amplifier performance before adding further stages to the receiver.
  • Page 62 4-13. Strip 1/8" insulation from the ends of the black and white wires of the 2-conductor speaker cable. Solder the stripped ends to the two terminals of the 3" speaker supplied in the kit. (White is "+", black is "-", but speaker polarity is not critical in this application.) 4-14.
  • Page 63 4-17. Reconnect the 15 volt DC supply to J1 as for the phase 3.0 VCO tests. For this test, re-attaching the Display Board is optional, but DO connect the power switch plug to J2. If you do attach the display board, handle the volume control gently. 4-18.
  • Page 64 Install the following ceramic disc capacitors: 4-29. Capacitor C37, 150 pF (marked 151). 4-30. Capacitor C36, 220 pF (marked 221). 4-31. Capacitor C40, 180 pF (marked 181). 4-32. Capacitor (marked 104). 4-33. Capacitor 4-34. Capacitor C46, also 4-35. Capacitor 4-36. Capacitor 4-37.
  • Page 65 Section 4C: IF Amplifier and AGC 4-50. Install U8, a MC1350P 8-pin DIP IC, being the notched or dotted end as outlined on the board. 4-51. Install U9, a MC1350P 8-pin DIP IC, being the notched or dotted end as outlined on the board. 4-52.
  • Page 66 4-75. Capacitor 4-76. Capacitor 4-77. Capacitor 4-78. Capacitor 4-79. Capacitor 4-80. Capacitor 4-81. Capacitor 4-82. reserved 4-83. Install electrolytic capacitor with correct ( + ) polarity. Final (4C) Phase 4.0 Progress Test Some technicians may feel the only way to fully prove to all your senses that all the circuitry built in Phase 4.0 is working properly is to see if a nearby 455 kHz signal can be detected.
  • Page 67 4-88. If there is NO or very little sound in SSB mode, there is a problem in the circuitry associated with U7, the Product Detector. 4-89. If you get the above-described result, turn off DC power, disconnect all cables from the 1254 board, set aside the display board, and proceed to Phase 5.0! If not, please read on.
  • Page 68 This space is for your notes 1254 Assembly...
  • Page 69 Phase 5.0 Schematic Details 1254 Assembly - 48...
  • Page 70 Phase Second Mixer and 45 MHz First IF The result of successful completion of this assembly phase will be a receiver circuit capable of detecting very strong nearby 45 MHz signals in either AM or SSB-CW mode. The Model 1254 has a built-in 45.000 MHz test signal capability.
  • Page 71 Phase 5.0 QUICK-REFERENCE INFORMATION 75 pF Second LO output filter 15 pF Output coupling cap from Q4 Source bypass cap on Q4 47 pF Resonating cap on input of Q4 Input cap to FL1 47 pF Resonating cap on input to FL1 Gate-2 bypass on Q4 33 pF Second LO capacitor at Q6 base...
  • Page 72 Phase 5.0 Assembly Steps Before You start: The preceding Quick Reference Summary of the parts used in Phase 5.0 may be used first as a guide to gathering parts for this phase. It is provided as an extra help in double-checking correctness of parts values with brief notes on the function of each part.
  • Page 73 Install the following 1/4-watt resistors: 5-11. Resistor R54, 100 ohms (brown-black-brown). 5-12. Resistor R83, also 100 ohms. 5-13. Resistor R84, also 100 ohms. 5-14. Resistor R86, also 100 ohms. 5-15. Resistor R60, 220 ohms (red-red-brown). 5-16. Resistor R75, also 220 ohms. 5-17 Resistor R77, 1K (brown-black-red).
  • Page 74 5-49. Install the unshielded slug-tuned coil L9, being sure it is seated squarely on the board before soldering. 5-50. Install the unshielded slug-tuned coil L10, being sure it is seated squarely on the board before soldering. 5-51. Slip the smallest shield can over L11 and the two larger shield cans over L9 and L10.
  • Page 75 5-56. Install FL1, the 45 MHz crystal filter (45U1A), which looks like a small crystal but with three leads. 5-57. Slip a base insulator over the leads of crystal Y3. 44.545 MHz, then install Y3 in the normal manner. 5-58. Install 10K potentiometer R82, the Clarifier control. Before soldering, make sure the control is mounted squarely against the board, to assure proper mating to the display board.
  • Page 76 5-64. Touching the probe as explained above should cause a very distinct increase in background noise level. Adjust coils L9 and L10 for maximum noise level. If you can do this, you have confirmed that there is a functioning signal path from C55 through all the circuitry you installed in Phase 4.0 and 5.0 to the audio amplifier.
  • Page 77 Phase 6.0 Schematic Details 1254 Assembly - 56...
  • Page 78 Phase 6.0 QUICK-REFERENCE INFORMATION Coupling cap into Q27 Supply bypass for Q27 10 pF 1st LO output filter 10 pF " " " Source bypass on Q27 2 pF 1st LO output filter 18 pF 8 pF Resonating cap on mixer T6 Supply bypass on first mixer RF bypass on mixer transformer "...
  • Page 79 Phase RF Input Circuit and First Mixer For your convenience, the complete hoard drawing for Phase 6.0 is presented on Page 62 after we finish the two shielded sections for which separate drawings are provided. Phase 6.0 Assembly Before You Start: The preceding Quick Reference Summary of the parts used in Phase 6.0 may be used first as a guide to gathering parts for this phase.
  • Page 80 Install these mylar film capacitors: 6-1. Capacitor (marked 222). 6-2. Capacitor 6-3. Capacitor Install these ceramic disc capacitors: 6-4. Capacitor C94, 20 pF. 6-5. Capacitor C95, 20 pF. 6-6. Capacitor C70, 47 pF. 6-7 Capacitor C73, 47 pF. 6-8. Capacitor C71, 180 pF (marked 181). 6-9.
  • Page 81 6B. Shielded First Mixer Section This circuitry will be enclosed within a shield just like the VCO's. Therefore, careful attention to correct parts selection is especially important. Figure 6.2 is provided for your convenience. The complete Phase 6.0 parts placement drawing is on page 58. Figure 6.2 6-20.
  • Page 82 Install the following ceramic disc capacitors: 6-24. Capacitor C57, 8pF. 6-25. Capacitor C60, 0 (marked 104). 6-26. Capacitor 6-27. Capacitor NOTE: There is an unlabeled outlined for a capacitor next to C57 which would serve as a shunt across trifilar balun T9. However, further engineering determined no capacitor is needed here, and this is the-only such "vacancy"...
  • Page 83 6C. Components Outside the Shielded Enclosures Figure 6.3 Install these 1/4-watt resistors: 6-31. Resistor R34, 47 ohms (yellow-violet-black). 6-32. Resistor R35, 100 ohms (brown-black-brown). 6-33. Resistor R56, also 100 ohms. 6-34a. Resistor R36, 220 ohms (red-red-brown). 6-35. Resistor R71, also 220 ohms. 6-36.
  • Page 84 Ceramic disc capacitors, cont. 6-48. Capacitor 6-49. Capacitor C76, (marked 104). 6-50. Capacitor 6-51. Capacitor 6-52. Install electrolytic capacitor with correct polarity. 6-53. Install 3.9v zener diode D17 , type 1N748A. (Review p. 62 if you have any question about identifying this diode.) Install these molded inductors: 6-54.
  • Page 85 Phase Final Assembly of Model 1254 Receiver ALIGNMENT SUGGESTION: The completed Model 1254 Receiver can indeed be fully aligned and tested NOW while still in "board form" before adding the front panel and other hardware. Doing it this way seems advisable ONLY if you have nagging doubts about a previous circuit phase test and if you feel the added hardware might interfere with testing and possible parts replacement in confined...
  • Page 86 7-4. Make sure none of the LED wires have been bent. 7-5. Set the display lens in position, making sure that the "AM-SSB" lettering is facing correctly. The lens is locked into place by carefully melting with your soldering tip the 6 molded posts inside the panel along the sides and bottom of the lens.
  • Page 87 Glue is also used to secure the TEN-TEC logo and to mount the speaker to its aluminum support shelf. You may wish to study those instructions and take care of those chores now.
  • Page 88 7-11. Tighten all 5 Display Board mounting screws. 7-12. Install the the Volume and Clarifier control knobs. Before tightening the setscrews, line up the index stripes correctly in reference to the silkscreened dot markings on the panel. 7-13. The large Tuning knob can be mounted to the encoder shaft in any way convenient to you.
  • Page 89 7-16. Mount the RIGHT side panel to the board using two 1/4" #4-40 screws and two #4 lock washers. 7-17. Secure the front panel to the right side panel using two #4-40 undercut screws. 7-18. Mount the rear panel to the ends of the two side panels, using four 1/4"...
  • Page 90 7-27. If needed, re-adjust L3 for a VCO voltage of 2.5 volts DC at 100 kHz. As you observed in Phase 3.0, increasing the frequency will increase the VCO voltage to a maximum of about 8.0 volts at 13.2 MHz. 7-28.
  • Page 91 7-39. Recheck all screws for reasonable tightness. 7-40. With considerable pride, attach the TEN-TEC logo to the front panel in the corner above the microphone jack. Use a bit of contact cement on the back of the logos and between the two mounting holes.
  • Page 92 This completes construction of the T-KIT Model 1254 SWL Receiver. We thank you very much for your trust in T-KIT products by TEN-TEC! See REFERENCE SECTION, Part III of this Manual, For all Model 1254 Operating Instructions,...
  • Page 93 This space is for your notes 1254 Assembly - 72...

  • Page 94: Model 1254 Operating Instructions

    Section 3: REFERENCE INFORMATION for T-KIT Model No. 1254 SSB-CW-AM Microprocessor-Controlled 100 kHz - 30 MHz Receiver Specifications: T-KlT Model 1254 Model 1254 Operating Instructions Functions of Primary Controls Tuning AM signals Storing Frequencies in Memory Recalling or Tuning Memory Frequencies...
  • Page 95 Model 1254 Receiver Specifications and Features Frequency coverage: 100 kHz to 30 MHz Modes: AM, SSB/CW Main Tuning: Normal or Fast tuning (2.5 kHz SSB, 5.0 kHz AM, or 100 kHz steps for either mode) "Clarifier" Control: for ± 1.5 kHz SSB/CW fine tuning between 2.5 kHz steps.

  • Page 96: Tuning Am Signals

    Model 1254 Receiver Operating Instructions 1. Control Functions The TUNE control performs two functions: Direct frequency tuning Memory Tuning (Memories 01 through 15) The VOLUME control sets the receiver audio gain. The CLARIFIER control permits fine-tuning of SSB and CW signals within the 2.5 kHz tuning steps in SSB mode.

  • Page 97: Storing Frequencies In Memory

    3. Storing Frequencies in Memory To place the currently displayed frequency and reception mode in memory, do the following: Press [MW]: the most-recently addressed memory location will be displayed. Rotate the TUNE control to the memory you wish to use, either an empty location or to replace an unneeded frequency.

  • Page 98: Tuning Ssb Signals

    5. Tuning SSB Signals Set the Clarifier control to its 12:00 position. Select SSB Mode and tune to a signal of interest. Use the Clarifier control to adjust for intelligible voice audio. Tune up (clockwise) for USB signals and down for LSB signals. If you are tuning the Clarifier clock- wise and the signal still seems "out of reach,"...

  • Page 99: Circuit Description

    Model 1254 Receiver Circuit Description Before we begin a stage by stage description of the circuitry in this receiver, let's take a broader view of how shortwave receivers are designed in general. This should help show how signals actually make their way from the antenna to the speaker. Depending on their intended function, radio receivers can be designed using several different electronic architectures.
  • Page 100 processing. This is illustrated with some example spectrum plots in Figure 2R. Fig. 2R: Spectrum Plot examples The stage of selectivity and gain that follows the mixer is called the intermediate frequency (IF) amplifier. Notice how the position of the local oscillator determines which part of the incoming spectrum falls within the bandwidth of the IF amplifier.

  • Page 101: Block Diagram

    Figure 3R: Model 1254 Block Diagram 1254 Reference - 8...
  • Page 102 The first stage in the Model 1254 is an input bandpass filter. Since we are not interested in signals beyond the 0.100 to 30 MHz tuning range of the receiver, this filter protects the mixer from energy outside this range. In particular, the filter must suppress any energy that occurs at the first IF frequency- We would not want input signals at the IF frequency leaking-past the first mixer and directly into the IF amplifier.
  • Page 103 This brings us to the first mixer stage which is made up of JFET transistors Q2 and Q3 and transformers T6 and T9. This circuit takes an incoming signal and combines it with the local oscillator to create a replica that is shifted up to the first IF frequency of 45.000 MHz.
  • Page 104 to a level sufficient to drive the diodes. A variable capacitance diode, "varactor", in series with the crystal gives this oscillator approximately ± 1.5 kHz of adjustment range for fine tuning. This varicap device exhibits a variable capacitance depending on the reverse bias voltage from the front panel clarifier control.
  • Page 105 Microchip Technology PIC series of CMOS micro- controllers. The device's 2K ROM is permanently programmed at TEN-TEC with the instruction code to run the receiver's numerous features and the chip's 80 byte RAM provides room to store 15 frequencies.
  • Page 106 only one digit is actually lit at a time. The processor continuously scans through all six digits very rapidly however so they appear to be lit simultaneously. As each digit is enabled by the high current driver IC U5, the processor feeds a BCD output to the 7 segment decoder U4.
  • Page 107 the phase detector. This division ratio is programmed into the reference divider at power on and sets the size of the tuning steps. The other input to the phase detector comes from a second divider that monitors the LO output. Its division ratio depends on the receiver frequency and is automatically updated by the processor as the receiver is tuned up or down.

  • Page 108: Connecting Antennas

    CONNECTING ANTENNAS The Model 1254 receiver is designed to work best with 50-ohm antennas resonant at the desired receiving frequency. In practice, a wide variety of antenna designs, both indoor and outdoor, will give good results. Receive-only antennas may be modeled on various ham radio transmit designs but may be constructed with lighter, less expensive materials such as hookup wire and TV/VCR coax or even lightweight shielded audio cable.
  • Page 109 Antenna Resources for Beginners: Antenna experimentation, design and maintenance are at the heart of the hobby of ham radio. Experienced hams or avid SWL's in your own town are probably the best resource for help in planning and putting up a SWL antenna suitable for your particular residence.

  • Page 110: Active Antenna Notes

    "Active" Antennas As already mentioned, any antenna should be located as far away from the receiver as possible to minimize multiplexing interference generated by the receiver itself . This applies especially to "active" antenna devices, both commercially- designed and homemade. The least expensive active antenna on the market is the T-KIT Model 1552, a module board kit supplied without enclosure or telescoping whip.
  • Page 111 Antenna Connection and Switching Suggestion The RCA-type phono jack on the rear panel of the Model 1254 is intended for "normal use," which means occasional plugging and unplugging a lightweight shielded cable terminated in an RCA- type plug. It is not designed to withstand repeated manipulation of, for example, RG-8 coax with a PL259 plus the required phono plug adapter.

  • Page 112: Dc Power Supply Considerations

    DC POWER SUPPLY Considerations For immediate convenience, the Model 1254 Receiver is supplied with a wall-type 15VDC 800 mA power supply. The 1254 receiver is also designed to operate from any 12 to 16 volt properly-filtered DC power source or a suitable vehicle battery system.

  • Page 113: Mobile Swling

    Mobile SWLing The rugged steel case and 12VDC power requirement of your receiver might give you the idea that the Model 1254 would be a nice addition to a car, RV, etc. We think this receiver is ideal for such installations for those very reasons. The center holes in the sides of your receiver case match threaded inserts in the chassis which will accept standard #6-32 machine screws.

  • Page 114: External Audio Connections

    Listening to a signal while observing the computer screen will help you gain the knack of proper tuning. TEN-TEC Technical Assistance cannot provide further information on data-related devices connected to the receiver.

  • Page 115: Swl Basics And Communications Applications

    SWL Information and Logging Any issue of the Popular Communications or Monitoring Times magazines will provide plenty of basic information on Short Wave Listening (SWL) as a hobby with enthusiasts worldwide. Like amateur radio, there are various specializations within the SWL hobby such as collecting OSL cards, listening for exotic broad- casts or to communications from airliners, embassies, world hot spots, revolutionaries, "pirate"...

  • Page 116: Beyond 30 Mhz

    Beyond 30 MHz . . . Your Model 1254 can be used with a receiving converter or even a transverter to receive VHF signals, particularly on the amateur 6 meter (50-54 MHz) and 2 meter {144-148 MHz) bands. The following T-KIT products will work nicely with the Model 1254 to permit monitoring of the 6 meter and 2 meter bands.
  • Page 117 SOME HELP WITH TERMS & ABBREVIATIONS The following are intended to be helpful descriptions, not formal definitions. We try to use plain language as much as possible in this manual, avoiding unnecessary jargon. Active Antenna A combination of a very short antenna, such as a telescoping whip, and electronic circuitry designed to correct shortened antenna impedance mismatch and provide amplification or gain.
  • Page 118 FILTER-ACTIVE FILTER-CERAMIC FILTER-CRYSTAL Filters are used in DC, Audio and RF FILTER-HI-PASS circuits. Understanding them is essential FILTER-LOW-PASS electronics know-how. FILTER-BANDPASS FILTER-PASSIVE FREQUENCY SYNTHESIS frequencies are a crystal oscillator or the L-C oscillator where the frequency is determined by coil (L) and capacitor ©. However we can process the output of an L-C oscillator through digital circuitry to simulate many different, precise crystal-like frequencies, using only one crystal as a reference standard.
  • Page 119 filter smooths out these pulses into a clean DC control voltage for the VCO. (See: VCO) see HIGH. LSB (Lower Sideband) See SSB. A miniaturized computer circuit capable of being programmed to perform control functions in a circuit. In the Model price of this receiver.
  • Page 120 PRESCALE, Prescaler a circuit or device which divides an incoming frequency down to a lower frequency so that it can be handled more easily by later digital counting circuitry or devices. This function is built into U3. REFERENCE FREQUENCY a precise, known frequency, usually crystal controlled, compared with another frequency, as is done in a PLL circuit.

  • Page 121: Terms & Abbreviations 24

    TRIMMER either a capacitor or resistor, miniature and variable, intended to permit exact, final adjustment of circuit values. 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.

  • Page 122: Component Reference Index

    T-KIT Model 1254 Receiver COMPONENT REFERENCE INDEX (See Kit Parts List for TEN-TEC part numbers not repeated below.) CAPACITORS (el. = electrolytic; film = mylar film; all others are disc ceramic) Reference Description Step No. Part No. Circuit Notes: 470/16v el.
  • Page 123 Reference Description Step No. Part No. Circuit Notes: 75 pF 5-32 23382 Second LO output filter 180 pF 4-31 23389 Coupling cap into U7 4-77 23261 Input bypass on U9 23261 High frequency shunt on U8 470/16v el. 4-5a 23228 Audio output coupling cap 4-33 23261...
  • Page 124 Reference Description Step No. Part No. Circuit Notes: 56 pF 5-31 23379 Output resonating cap for Q4 75 pF 5-33 23382 Second LO output filter 5-41 23260 Supply bypass for Q5 6-50 23261 RF bypass on AGC diode D14 2-24 23261 Supply bypass for U2 5-42...
  • Page 125 INDUCTORS Reference Description Step No. Part No. Circuit Notes: 2-40 21164 RFC for U3 DC supply VCO coil 3-18 85421-1 VCO-2 coil VCO coil 85421-2 VCO-1 coil 3-56 21105 PLL feedback lowpass filter 3-57 21107 " " " " 6-55 21120 LO amplifier DC choke 6-54...
  • Page 126 Reference Description Step No. Part No. Circuit Notes: 2N4124 25258 Second LO buffer 2N4124 5-10 25258 Second LO oscillator J310 5-55 25115 455 kHz amplifier 2N4124 4-21 25258 AM detector 2N4124 4-52 25258 AGC rectifier 2N5087 4-54 25001 AGC integrator 2N4124 4-53 25258...
  • Page 127 Reference Description Step No. Part No. Circuit Notes: 3-11 20157 VCO switching 3-41 30122 Supply resistor for Q25 3-50a 30150 Base bias for Q25 3-50b 30150 Bias for Q26 3-44 30134 Emitter resistor for Q26 3-51 30150 Bias resistor for Q26 6-33 30150 Gate Pull-down for Q27...
  • Page 128 Reference Description Step No. Part No. Circuit Notes: 5-24 20157 Clarifier varactor bias 5-21 30154 Second LO bias 5-22 30154 Second LO bias 5-25 20157 Gate 2 bias for Q4 10K var 5-58 30267 Front panel clarifier pot 5-12 30126 Supply feed for Q4 5-13 30126...

  • Page 129: Troubleshooting Guide

    Model 1254 Receiver TROUBLESHOOTING GUIDE This section presumes that the receiver has been working and that you now suspect a problem. Problems encountered DURING kit assembly phases should be corrected before progressing to the next assembly phase. 1. Look for the simple and obvious first: Power supply or batter connection problem Blown power supply fuse Broken antenna coax connection...
  • Page 130 TEN.TEC is the sole source is the pre-programmed U2 microprocesser IC and the fabricated steel, aluminum or plastic parts 0f the enclosure. All parts used in the receiver may be ordered by TEN-TEC part number as specified in the Parts List or Component Index. Minimum order charges may be applicable.

  • Page 131: Chart Of Significant Voltages

    Model 1254: Selected DC Voltage Measurements Measuring point Typical VDC Your reading Q5 base Q7 course (at R86) T7 (cold end) U9 pin 4 pin 6 (measuring here will generate noise) pins 1 and 2 U8 pin 4 pin 6 (measuring here will generate noise) pins 1 and 2 T3 (measure at anode of D12) D7 cathode...

  • Page 132: Modification Notes

    Modifications to the Original Receiver Design It is in the very nature of hobby electronics to "customize" equipment, especially that which we build ourselves. It is good practice, to make written notes about any changes or additions you make to the original design, even simple ones such as auxiliary DC, audio or antenna connections.

  • Page 133: Checking For Solder Bridges

    CHECKING FOR SOLDER BRIDGES This view of the main circuit board solder-side traces is exactly as you would view the board itself, with no need to look "through" the board from top to bottom. If you wonder whether certain points should be joined by solder, compare what you see on the board with this view of the traces.
  • Page 134 T-KIT Limited Warranty Please read carefully BEFORE building your Kit This limited warranty applies solely to KITS sold by TEN-TEC, Inc. under the trade name :T- products of any kind manufactured by TEN-TEC Inc., nor shall any other warranties published by TEN-TEC Inc., or any TEN-TEC customer service policies for its manufactured products, be construed as applicable to T-KIT products.
  • Page 135 9. TEN-TEC, Inc. reserves the right to revise this limited warranty, to change or discontinue any kit product or revise its instruction manual with no liability to previous purchasers.

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