20 MTR 20 WATT QRP LINEAR AMPLIFIER KIT Ramsey Electronics Model No. QAMP20 Need a little extra boost for your QRP rig? Believe it or not, 20 watts is only about an `S' unit below a 100 watt rig! This nifty little amp will add some "punch" to any QRP transmitter. · · · · · · · · Works great with Ramsey QRP rigs or any other 1-2 watt transmitters Built-in T/R relay automatically switches between receive and transmit Runs on 12 volts DC at 2 to 4 amps; ideal for field day or battery operation Multistage low pass filter for a clean signal Operates all modes: CW, SSB, or AM Fast, easy, and fun 2 hour assembly Informative manual answers questions on theory, hook-ups, and uses - enhances resale value too! Clear, concise assembly instructions carefully guide you to a finished kit that works the FIRST time! QAMP20 · 1 RAMSEY TRANSMITTER KITS · FM10A, FM25B FM Stereo Transmitters · TV6 Television Transmitter · Cube TV Transmitters RAMSEY RECEIVER KITS · FR1 FM Broadcast Receiver · AR1 Aircraft Band Receiver · SR2 Shortwave Receiver · AA7 Active Antenna · SC1 Shortwave Converter RAMSEY HOBBY KITS · SG7 Personal Speed Radar · SS70A Speech Scrambler · TT1 Telephone Recorder · SP1 Speakerphone · MD3 Microwave Motion Detector · PH10 Peak hold Meter · LC1 Inductance-Capacitance Meter RAMSEY AMATEUR RADIO KITS · DDF1 Doppler Direction Finder · HR Series HF All Mode Receivers · QRP Series HF CW Transmitters · CW7 CW Keyer · CPO3 Code Practice Oscillator · QRP Power Amplifiers RAMSEY MINI-KITS Many other kits are available for hobby, school, Scouts and just plain FUN. New kits are always under development. Write or call for our free Ramsey catalog. QAMP20 QRP CW POWER AMPLIFIER KIT INSTRUCTION MANUAL Ramsey Electronics publication No. MQAMP20 Revision 1.5a First printing: January 1993 COPYRIGHT 1994 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York 14564. All rights reserved. No portion of this publication may be copied or duplicated without the written permission of Ramsey Electronics, Inc. Printed in the United States of America. QAMP20 · 2 Ramsey Publication No. MQAMP20 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR 20 METER QRP CW POWER AMPLIFIER KIT TABLE OF CONTENTS Introduction to the QAMP20........... 4 How it works................................... 4 Parts list ......................................... 5 Learn as you Build ......................... 6 QAMP20 assembly instructions ..... 7 Initial tests ..... .............................. 12 Verifying RF output power ........... 13 Troubleshooting tips..................... 15 Using the QAMP20 ...................... 16 Parts layout diagram .................... 17 Schematic diagram ...................... 18 Ramsey kit warranty .................... 19 RAMSEY ELECTRONICS, INC. 590 Fishers Station Drive Victor, New York 14564 Phone (585) 924-4560 Fax (585) 924-4555 www.ramseykits.com QAMP20 · 3 INTRODUCTION The Ramsey QAMP series of QRP power amplifiers are compact 10 to 20 watt RF amplifiers for QRP CW transmitters. These amplifiers are made to be driven by transmitters in the ½ to 2 watt range. Built-in to the power amplifier is a sensitive T-R relay which will switch the unit in and out of the antenna line. When in receive, the amplifier is bypassed and the antenna feeds directly to the input jack. When you go to transmit, the T-R circuit detects the transmit RF power and automatically switches the power amplifier into the circuit and amplifies the applied RF power. If you decide to run "barefoot", turning off the QAMP will disable the amplifier and your QRP transmitter will feed directly through the amplifier without any amplification. Power is supplied by any 12 to 15 volt DC source with a current draw of 1 to 3 amps depending upon RF power output. A 5 pole low pass filter using toroid cores keeps harmonics and spurious signals very low. The entire amplifier is very easy to construct, but does require you to wind a few coils and RF transformers - we'll lead you step-by-step through all steps! HOW IT WORKS The QRP amplifier is very simple with most of the "magic" being done by just a few parts, the pair of MOSFET transistors and the ferrite wideband transformers. Transformer T2 matches the 50 ohm amplifier input to the push-pull inputs of the FET transistors. The term push-pull means that one transistor amplifies the positive portion of the input signal while the other transistor amplifier the negative portion - put another way, one is pushing while the other is pulling! The center tapped transformer splits the input signal so each transistor will only amplify the correct part of the input signal. Incidentally, this push-pull technique has been used for years in both vacuum tube and solid-state gear. The push-pull signal output from the FETs is combined and impedance matched to 50 ohms by ferrite transformer T1. To reduce any harmonic content, a 5 pole low pass filter consisting of L1,2,3 and C4,5,6,7 is used. The FET transistors are biased "on" slightly for best gain and linearity. Zener diode D1 provides a constant voltage for the bias network R2,3,4. Bias pot R4 allows adjustment of bias voltage to the FET transistor gates. It is adjusted for a set amount of current through the transistors. The T-R relay circuit uses a simple diode detector consisting of D2 and D3. The detector output is amplified by transistors Q3 and Q4 to drive relay K1. QAMP20 · 4 PARTS LIST FOR THE QAMP20 QRP POWER AMPLIFIER CAPACITORS: 1 1 4 2 2 2 1 3 1 2 1 1 2 1 1 1 100 to 220 µf electrolytic capacitor [C1] 10 µf electrolytic capacitor [C2] .1 µf disc capacitors (marked .1 or 104) [C3,8,10,13] 180 f disc capacitors (marked 180 or 181) [C4,7] 330 f disc capacitors (marked 330 or 331) [C5,6] .001 µf disc capacitors (marked .001 or 102 or 1000) [C11,12] .01 µf disc capacitor (marked .01 or 103 or 10 nf) [C9] 1 K ohm resistors (brown-black-red) [R1,5, TP1] 6.8 K ohm resistor (blue-gray-red) [R2] 10 K ohm resistors (brown-black-orange) [R3,12] 470 ohm resistor (yellow-violet-brown) [R6] 100 K ohm resistor (brown-black-yellow) [R7] 270 ohm resistors (red-violet-brown) [R8,9] 51 ohm resistor (green- brown-black) [R10] 2.2 K ohm resistor (red-red-red) [R11] 5 K potentiometer (marked 502M) [R4] RESISTORS: SEMICONDUCTOR DEVICES: 1 2 1 2 2 1 Zener diode, 6.2 volt (gray body with black band) [D1] 1N4148 type signal diodes (glass body with black band) [D2,3] 1N4002 style black epoxy diode [D4] Power MOSFET transistors (marked P16NF06) [Q1,2] 2N3904 NPN transistors [Q3,4] 221334 PNP transistor [Q5] OTHER COMPONENTS: 1 1 2 1 2 3 1 1 1 7' 2 2 Relay DPDT 12 volt [K1] PC mount pushbutton switch [S1] RCA style PC mount phono jacks [J1,2] 2.5 mm DC power jack [J3] Heatsink [HS1,2] Yellow toroid coil core [L1,2,3] 10 µH inductor [L4] 2 hole small ferrite transformer core [T2] 2 hole large ferrite transformer core [T1] #24 enameled magnet wire (thin wire) [for winding L1,2,3 and T1,2] 4-40 x ¼" machine screw 4-40 hex nut QAMP20 · 5 REQUIRED, NOT SUPPLIED: Ramsey case, knob and panel set, Ramsey part no. CQRP Matching input and output cables to existing QRP transmitter 12 volt DC power supply 3 amp rating Proper dummy load or resonant antenna "THE RAMSEY LEARN-AS-YOU-BUILD ASSEMBLY STRATEGY" Take a look at the parts layout diagram. There is quite a lot to the construction of the QAMP20. It's easier than it seems once you get going, especially after you have installed a few of the "landmark" components. Once these "landmark" components are placed, other parts' positions are referenced to them, and construction goes quite smoothly. This will help in relating from one part to another what specific holes it may require on the board, and that part's orientation. In addition, we will discuss the purpose of most components or groups of components as we go along. This is the Ramsey Learn-As-You-Build kit assembly philosophy. Be sure to read through all the steps, and check the boxes as you go to be sure you didn't miss any important steps. Most of the problems we find here at the factory are due to faulty assembly, no matter how experienced the builder may be: it's especially tough to tell a 30 year experienced ham that he goofed! Before you run the circuit, check all diodes and polarized capacitors for proper orientation. TIPS AND NOTES: Use a good soldering technique - let your soldering iron tip gently heat the traces to which you are soldering. Heat both wires and pads simultaneously. Apply the solder on the iron, lead, and the pad when pad and wire is hot enough to melt the solder. The actual joint should look like a drop of water on paper (somewhat soaked in). Parts are mounted on the top side of the board. This is the side that has no traces or pads on it. Part orientation - All parts in this kit are mounted at 90 degree angles, meaning parts are either parallel or perpendicular to the sides of the board. Part installation - When parts are installed, the part is placed flat to the board, and the leads are bent on the backside of the board to prevent the part from falling out before soldering. The part is then soldered into place, and the spare leads are removed. Make sure lead lengths are as short as possible when dealing with the RF section of this kit. QAMP20 · 6 In all the following instruction steps, our word "INSTALL" means to do the following: · · Insert the part, oriented correctly, into its correct holes in the PC board. If helpful, gently bend the part's wire leads or tabs to hold it in place, with the body of the part snugly against the top side (component side) of the PC board. Solder all wires or pins of the part, whether the 2 wires of a resistor or the 3 or 4 wires of a transistor. · · Trim all excess wires extending beyond each solder connection, taking care that wire trimmings do not become lodged in PC board solder connections. CONSTRUCTION: Since you may appreciate some "warm-up" soldering practice as well as a chance to put some "landmarks" on the PC board, we'll first install some "hardware" components. 1. Install S1, PC mount pushbutton switch. Solder all 6 pins securely. 2. Install J1and J2, PC mount RCA phono jacks. Solder all 4 pins on each securely as these connectors will be subjected to some stress when coax cables are connected to them. 3. Install J3, PC mount DC power jack. 4. Install relay K1. Notice that it installs only one way. 5. Install potentiometer R4. This pot allows adjustment of the bias to the power transistors. 6. Install C9, .01 µf disc capacitor (marked .01 or 103 or 10 nf). 7. Install Q5, 221334 PNP transistor, with the flat side oriented toward D2. 8. Install R6, 470 ohm resistor (yellow-violet-brown). 9. Install R10, 51 ohm resistor (green-brown-black). 10. Install R11, 2.2 K ohm resistor (red-red-red). 11. Install R12, 10 K ohm resistor (brown-black-orange). 12. Install D2 and D3, 1N4148 style signal diodes (glass body with black band). Pay special attention to the banded ends. The banded end on a diode is the cathode and must be oriented correctly or the circuit will not work. Both diode D3 and diode D2 are detectors for sensing applied RF power. 13. Install C10, .1 µf disc capacitor (marked .1 or 104). 14. Install R7, 100 K ohm resistor (brown-black-yellow). QAMP20 · 7 15. Install Q3 and Q4, 2N3904 NPN transistors, observing proper orientation of the flat side. These two transistors amplify the signal diode's output to a level high enough to close relay K1. 16. Install diode D4, 1N4002 style black epoxy diode. Check positioning of the banded end. 17. Install jumper JMP2. Use a piece of scrap component lead wire bent into a "staple" shape and inserted into the board like a component. Jumpers act as electronic "bridges" carrying signals over PC board circuit traces underneath. 18. Install C13, .1 µf disc capacitor (marked .1 or 104). 19. Install L4, 10 µH inductor (green body with brown-black-black bands). 20. Install R3, 10 K ohm resistor (brown-black-orange). 21. Install C2, 10 µf electrolytic capacitor. Electrolytic capacitors are polarized with a ( + ) and a ( - ) lead and must be installed correctly for proper operation. Generally, capacitors have their ( - ) lead marked with a black stripe while PC boards have the ( + ) hole indicated. 22. Install D1, 6.2 volt Zener diode (gray body with a black band). This diode provides a stable voltage which is used to provide bias for the power transistors. 23. Install R5, 1 K ohm resistor (brown-black-red). 24. Install R2, 6.8 K ohm resistor (blue-gray-red). 25. Install R1, 1 K ohm resistor (brown-black-red). 26. Locate another 1 K ohm resistor (brown-black-red). Trim back one lead to a length of ¼ inch. Bend this wire into a small loop as shown. This loop will act as a convenient point to connect a test probe for setting the bias voltage. Insert the resistor into the PC board and hold it carefully while you solder it to the board. 27. Install R8, 270 oh ...