Vectronics QRP CW Transmitter Kit - Owner's Manual

IMPORTANT WARRANTY INFORMATION

Return Policy on Kits When Not Purchased Directly From Vectronics: Before proceeding with your VEC kit, consult your Dealer regarding their return policy. If returns are permitted, the kit must be returned in its pre-assembled condition.

Return Policy on Kits When Purchased Directly From Vectronics: Kits returned to the factory must be in their pre-assembled condition. Once assembly and soldering begin, the builder assumes the role of the manufacturer. Vectronics cannot be held accountable for the quality or outcome of the builder's work. Returns are not accepted for kits in progress or completed work as a warranty item. New or inexperienced builders are urged to read the manual carefully. Kits may be returned within ten (10) working days of arrival, provided construction has not begun.

Vectronics Warrants: Each kit contains the items specified in the parts list.

Missing Parts: If a part is missing during pre-construction inventory, contact Vectronics for a free replacement. Double-check markings and ensure an alternative part has not been substituted. Vectronics reserves the right to make substitutions if a part is unavailable or a more suitable alternative exists, usually noted in a manual addendum.

Defective Parts: If a part is found to be broken or unserviceable during inventory, return it to Vectronics with an explanation. Upon testing, if found defective and unused, a new part will be shipped free of charge.

Missing or Defective Parts After Assembly Begins: Parts lost or damaged after construction starts are not covered. However, most parts are inexpensive and can be replaced by Vectronics for a reasonable charge. Contact the factory with a complete description.

Factory Repair After Assembly Begins: Kits in progress or completed kits are excluded from warranty. As a service, technicians are available for evaluation and repair for a minimum service fee of $18.00 (1/2 hour rate) plus $7.00 shipping and handling (prices subject to change). To qualify, the kit must be fully completed, unmodified, and assembled using rosin-core solder. Technicians will contact the customer before performing work exceeding one hour ($36.00). Ship defective units prepaid to: Vectronics, 1007 HWY 25 South, Starkville, MS 39759. Include minimum payment ($25.00 total) plus shipping and handling, a valid UPS return address, and a daytime phone number.

INTRODUCTION

This kit offers an introduction to QRP (low power) operation in amateur radio. The VEC QRP-CW Transmitter Kit is designed for ease of building and includes sophisticated features for enjoyable QRP operation. Features include a built-in diode antenna switch for full QSK operation, shaped keying, and crystal-controlled frequency stability with a wide-range VXO circuit. Each kit includes a crystal for the QRP calling frequency. The transmitter provides a solid 1-watt plus signal filtered through a high-Q toroid low-pass filter for FCC compliance.

TOOLS AND SUPPLIES

Construction Area: Requires a clean, well-lighted area. A sheet of white poster board is recommended for the work surface. Ensure adequate lighting and use a high-temperature stand for the soldering iron, keeping the area free of clutter.

Universal Kit-building Tools:

• Soldering Iron
• High-temperature Iron Holder with Cleaning Sponge
• Rosin-core Solder (thin wire-size preferred)
• Needle Nose Pliers or Surgical Hemostats
• Diagonal Cutters or "Nippy Cutters"
• Solder Sucker, Vacuum Pump, or Desoldering Braid
• Bright Desk Lamp
• Magnifying Glass

Special Tools for This Kit:

• RF power meter or VSWR bridge
• 50-ohm dummy load or 1-watt 47 ohm carbon-film resistor
• Telegraph key with a 3.5 mm "mini" phone plug
• LED (any color)

BEFORE YOU START BUILDING

Avoid common builder mistakes:

1. Installing the Wrong Part: Double-check part values (e.g., 1K vs. 10K resistors, capacitor codes like 102 vs. 103).
2. Installing Parts Backwards: Verify polarity for electrolytic capacitors (+ lead), transistors (flat side/emitter tab), ICs (notch/dot), and diodes (banded end).
3. Faulty Solder Connections: Inspect for cold-solder joints (insufficient heat) and solder bridges (excess solder creating shorts).
4. Omitting or Misreading a Part: Ensure each step is completed and parts are correctly identified.

Soldering Tips:

• Cleanliness and heat distribution are key. Ensure leads/pins are free of oxidation.
• Heat the lead and pad for ~1 second before applying solder.
• Apply solder sparingly to the connection, not directly to the iron tip.

Desoldering Tips:

• Grasp component with pliers, heat pad, and gently pull.
• Use a pin to clear solder-filled holes.
• Use desoldering braid or a vacuum bulb for ICs and multi-pin parts.
• Replace damaged or severely overheated parts.

Work Habits: Work for short periods when fresh and alert. Take your time and enjoy the process.

Sorting and Reading Resistors

Resistor values are indicated by a color code. The first two bands indicate the value, the third is the multiplier, and the fourth band indicates tolerance (gold = 5%, silver = 10%).

Resistor Color Code:

Sort resistors by multiplier band first, then by specific value. Molded chokes may resemble resistors but are typically larger in diameter.

Reading Capacitors

Capacitor values are printed on the body. Small values are in pF (pico-Farads), larger values in uF (micro-Farads). 1000 pF = 0.001 uF.

Three-Number Code: The first two digits are the value, the third is the multiplier (e.g., 103 = 10 x 10³ pF = 10,000 pF = 0.01 uF).

Electrolytic Capacitors: Marked in uF, polarized. The longer lead is positive (+). Ensure correct orientation during installation.

Diodes

Diodes are polarized. Install with the banded (cathode) end matching the PC board marking.

Transistors

Identification:

• Metal Case: Small tab near emitter indicates position.
• Plastic Case (TO-92): Flat side identifies mounting orientation.
• Tab-cooled Devices (TO-220): Cooling tab position indicates orientation.

Integrated Circuits (ICs)

Position ICs using the dot or square marking on the device, aligning it with the corresponding mark on the PC board. Pin numbers start at the keyed end and proceed counter-clockwise.

PARTS LIST

The parts list is divided into generic parts (common to all models) and specific parts for each kit model (VEC-1220K, VEC-1230K, VEC-1240K, VEC-1280K).

Generic Parts

Resistors:

Capacitors:

Chokes, Coils:

Semiconductors:

Jacks, Switches:

Miscellaneous Items:

VEC-1220K (20-Meter QRP-CW Transmitter Kit)

Capacitors:

Inductors/Chokes:

Crystal:

VEC-1230K (30-Meter QRP-CW Transmitter Kit)

Capacitors:

Inductors/Chokes:

Crystal:

VEC-1240K (40-Meter CW Transmitter Kit)

Capacitors:

Inductors/Chokes:

Crystal:

VEC-1280K (80-Meter CW Transmitter Kit)

Capacitors:

Inductors/Chokes:

Crystal:

If parts are missing, consult the warranty section. Once inventory is complete, you are ready to begin building. Remember, returns are not possible after construction begins.

Making copies of the parts placement and schematic diagrams for your work area is recommended. A parts placement layout is also printed on the circuit board.

PARTS PLACEMENT

Refer to the provided diagram for the location of each component on the printed circuit board.

STEP-BY-STEP ASSEMBLY

The kit construction is divided into three stages: installing small generic parts, frequency-determining components, and larger generic parts.

Install: Locate, identify, and insert the part into its mounting holes. Pre-bend leads as needed. Bend leads over to hold the part, then clip excess lead length before soldering. Ensure trimmed leads do not touch other pads or tracks.

Solder: Solder the part's leads and inspect connections for flaws or solder bridges. Trim excess leads.

Phase 1: Resistors

• Install two (2) 100 ohm resistors at R4 and R7.
• Install one (1) 270 ohm resistor at R8.
• Install three (3) 470 ohm resistors at R5, R9, and R11.
• Install one (1) 1K resistor at R10.
• Install three (3) 10K resistors at R1, R2, and R3.
• Install one (1) 47K resistor at R6.

Save clipped resistor lead ends for jumper leads.

Phase 2: Ceramic and Electrolytic Capacitors

• Install ten (10) .01 uF disc ceramic capacitors (marked 103) at C1, C3, C9, C10, C11, C12, C15, C17, C18, C21.
• Install one (1) .1 uF disc ceramic capacitor (marked 104) at C2.
• Install the 470 uF electrolytic capacitor (C4) observing polarity (longer lead is positive, matching PC board marking).

Phase 3: Jumpers

• Form and install four (4) jumper leads at JMP1 (11/32"), JMP2 (11/32"), JMP3 (3/8"), and JMP4 (1/4").

Save one resistor lead for connecting variable capacitor C5.

Phase 4: Chokes

• Install two (2) 100 uH chokes at RFC4 and RFC5.

Phase 5: Transistors and Diodes

• Install 2N3906 transistor (Q1) with flat side aligned to PC board marking.
• Install 2N3904 transistor (Q2).
• Install PN2222 transistor (Q3).
• Install 2N3053 transistor (Q4) with metal case resting on PC board, emitter tab towards R7.
• Install two (2) 1N4007 diodes (D1, D2) with the white band matching the PC board marking.
• Install 1N4148 diode (D3) with the banded end matching the PC board marking.

Save clipped lead ends from 1N4007s for supporting C5.

Phase 7: Frequency-Determining Parts

Installing Multilayer Capacitors: Pre-form leads to the correct spacing before installation. Avoid stressing leads during installation.

Winding and Installing Toroid Coil L1: Wind the specified number of turns (counted inside the form) tightly onto the T37-2 form. Trim leads to 1/2" and tin with solder. Install at L1.

VEC-1220K 20-Meter QRP-CW Transmitter Kit

• Install capacitors C6 (22 pF), C8 (47 pF), C16 (68 pF), C7, C19, C20 (220 pF), C14 (330 pF), C13 (470 pF).
• Install 1.8 uH chokes at RFC1, RFC2, RFC3.
• Wind twelve (12) turns for L1.
• Install 14.060 MHz crystal at Y1.

VEC-1230K 30-Meter QRP-CW Transmitter Kit

• Install capacitors C6 (33 pF), C8 (47 pF), C16 (100 pF), C7 (220 pF), C19, C20 (330 pF), C13 (470 pF), C14 (680 pF).
• Install 2.2 uH chokes at RFC1, RFC2, RFC3.
• Wind fifteen (15) turns for L1.
• Install 10.108 MHz crystal at Y1.

VEC-1240K 40-Meter CW Transmitter Kit

• Install capacitors C6 (47 pF), C8, C16 (100 pF), C7 (220 pF), C13, C19, C20 (470 pF), C14 (1000 pF).
• Install 4.7 uH chokes at RFC1, RFC2, RFC3.
• Wind eighteen (18) turns for L1.
• Install 7.040 MHz crystal at Y1.

VEC-1280K 80-Meter CW Transmitter Kit

• Install capacitors C6 (68 pF), C8, C16 (100 pF), C13, C16 (470 pF), C19, C20 (820 pF), C7, C14 (1000 pF).
• Install 10 uH chokes at RFC1, RFC2, RFC3.
• Wind twenty-two (22) turns for L1.
• Install 3.579 MHz crystal at Y1.

Phase 8: Completing your Kit

• Install two (2) DPDT push-button switches at SW1 and SW2.
• Install two (2) RCA jacks at J3 and J4.
• Install the 3.5 mm key jack at J1.
• Install the 2.1 mm DC power jack at J2.
• Secure the variable capacitor (C5) using double-sided tape and leads from 1N4007 diodes.
• Install a resistor lead between SW2 and C5's solder tab.
• Attach the TO-5 heat sink to Q4.
• Install the 1/2" tuning shaft extension onto the main tuning capacitor shaft.

PC Board Inspection (Quality Control):

• Compare part locations and values against the Parts Placement Diagram.
• Inspect solder side for cold joints and solder bridges. Joints should be smooth and shiny.
• Check polarity of electrolytic capacitors and diodes. Verify transistor installation (Q1-Q4).

TESTING AND ALIGNMENT

The VEC QRP-CW Transmitter is a "no-tune" design. If built correctly, it should work without alignment.

Tools and Materials Required:

• 50-ohm dummy load (or two 100-ohm 1-watt resistors in parallel).
• RF power meter or VSWR bridge.
• Telegraph key with a 3.5-mm stereo phone plug.
• Well-regulated 12-14 Volt, 500-mA DC power supply.
• RF Cables (RG-174 or RG-58) with appropriate connectors.

Test Set-up and Procedure:

1. Connect dummy load to ANT jack (J3). Connect key to J1. Connect power supply to J2 (observe polarity). Ensure power switch (SW1) is OFF and crystal select switch (SW2) is in the OUT position (Y1 selected).
2. Turn power switch SW1 ON. No RF output should be indicated.
3. Press the key. Power meter should indicate 1 watt or more.
4. Release the key; output power should drop to zero.
5. Press SW2 (in position) and key. There should be no output.
6. Return SW2 to OUT position.
7. Key the transmitter and find its signal with a receiver tuned to the approximate frequency.
8. Monitor the CW note for chirp, ripple, or key clicks.
9. Key and tune the VXO capacitor; the transmit frequency should shift.
10. Test receiver side of T/R switch: Connect LED across J4 (REC). Key transmitter. If LED does not illuminate, T/R switch is likely working.

If a wattmeter is unavailable, a standard 5 mm LED can indicate output when connected across the terminated antenna jack. The LED should illuminate brightly.

Troubleshooting Notes:

• Reverse power connection may blow the etched fuse trace near J2. Replace with wire or a 1A fuse.
• A "buzz" on the CW note may indicate power supply filtering issues or ground loops.
• VXO tuning range varies by band (e.g., ~7 kHz on 20m, ~1.5-2 kHz on 80m).

OPERATING INSTRUCTIONS

Connecting the VEC QRP-CW Transmitter:

1. Crystal Select (SW2): Selects calling frequency (Y1) or optional crystal.
2. VXO Tune (C5): Varies oscillator frequency.
3. Key Jack (J1): Accepts manual or electronic keys.
4. Power Switch (SW1): Applies power.
5. Power Jack (J2): For 12-14V DC @ 0.5A supply.
6. Antenna Jack (J3): RCA connector for 50-ohm antenna, rated for >1 watt output.
7. Receiver Jack (J4): Routes antenna to receiver via T/R switch.

Receiver Hook-up: Most receivers can be patched to J4 without damage. Transmitter output is ~+32 dBm; receiver input is ~+7 dBm. Use receiver attenuator if available; disable preamplifiers. Reduce receiver volume if necessary.

QRP Antennas: A good antenna is crucial for QRP. Full-sized dipoles or slopers, installed high and tuned for low VSWR, are recommended. The transmitter uses a broadband output network matching 50-ohm loads. The ARRL Antenna Handbook provides additional information.

Balun: A balun (coiled RG58) can help eliminate unwanted feedline radiation and noise pickup.

QRP Operating Tips:

• Use the "hunt-and-pounce" method: answer CQs and call stations that have just finished QSOs.
• Call CQ near the QRP calling frequency.
• Don't hesitate to call weak stations; they may also be operating QRP.

IN CASE OF DIFFICULTY

Troubleshoot systematically. Check power source, connections, polarity, and fuses.

• Does not power up: Check power source, cable, polarity of D1, fuse trace near J2.
• Does not key: Check key/plug, Q1/Q2 circuitry, Y1 installation, SW2 position.
• Weak Signal/No Output: Check Q3/Q4 circuitry, D2/D3 positions, Vcc on Q4, C13/C14 values, L1 winding.
• Chirp/Key-Clicks: Check Q2 circuitry, C1/R1/C2 values.
• Transmitter remains on: Check RFCs, Q3/Q4 circuitry, load connection.
• LED lights at J4 when keyed: Check D3 circuitry, test D3.
• VXO fails to shift: Check RFC1, C5 connections.
• Blown Crowbar Fuse: Usually caused by reverse power or short circuit. Replace fuse trace or use #32 wire.

Voltage Analysis: Use a voltmeter to check DC voltages at transistor leads. Disable oscillator Q2 by pushing SW2 IN before measurements. Compare readings to the provided VOLTAGE CHART.

VOLTAGE CHART:

If problems persist, repeat the QC check. Most issues are due to misplaced parts, incorrect polarity, improper transistor installation, or faulty solder connections. Kit repair services are available through Vectronics.

THEORY OF OPERATION AND SPECIFICATIONS

Technical Circuit Description:

The VEC QRP-CW Transmitter is a three-stage oscillator/amplifier with no tune-up requirement. Q1 is keyed by the input signal to power oscillator Q2, driver Q3, and T/R switching diode D2. Q2 is a crystal-controlled oscillator with VXO capability. Q3 drives power amplifier Q4. Q4 is a class-C amplifier. In transmit, the antenna line is routed via D2; in receive, via D3. A pi-section low-pass filter provides impedance matching and harmonic suppression.

Specifications:

• RF Power Output: 1.25 watts at 14 MHz
• Suppression: 35 dBc or better
• Receiver Isolation: -25 dBc
• VXO tuning range: 8 kHz at 14 MHz (less at lower frequencies)
• Stand-by current: 10-15 mA
• Transmit current: 250-350 mA at 13.8 Volts DC

ENCLOSURE

A matching metal enclosure (Model: VEC-1200KC) is available separately. Follow these instructions for installation:

1. Apply front and rear panel decals, cutting out holes carefully.
2. Install L-brackets on the chassis using 3/16" screws.
3. Install 1/2" mounting screws from the bottom.
4. Place 3/16" round spacers on mounting screws.
5. Insert the PC board at an angle, aligning controls with holes. Push down on the rear, aligning mounting screws with PC board holes.
6. Secure the PC board with four hex nuts. Ensure components are centered before tightening.
7. Place switch caps on SW1 and SW2. Place knob on C5, tightening the set screw if necessary.
8. Install the top cover using the remaining 3/16" screws.
9. Place the four rubber feet on the bottom corners of the enclosure.