20 METER (14MHz) CW TRANSMITTER Ramsey Electronics Model No. QRP20 THE RAMSEY QRP20 IS AN AMAZING PERFORMER THAT WILL WORK THE WORLD ON ABOUT A WATT! FOLKS OF ALL AGES HAVE SUCCESSFULLY BUILT AND ENJOYED THIS EASY, FUN KIT. • Ideal for portable or travel fun • VCXO design allows up to 8 - 10 KHz of tuning about the crystal frequency • Front panel switching of TWO channels and includes a crystal for 14.
RAMSEY TRANSMITTER KITS • The “Cube” MicroStation Transmitter • FM25B Synthesized FM Transmitter • FM100B Stereo FM Transmitter • AM1 AM Transmitter • AM25 Synthesized AM Transmitter 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 • BS1 “Bullshooter” Digital Voice Storage Unit • AVS10 Automatic Sequential Video Switcher • WCT20 Cable Wiza
Ramsey Publication No. QRP20 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR QRP20 20 METER CW TRANSMITTER KIT TABLE OF CONTENTS Introduction to the QRP20 ............. 4 Understanding Power Levels ......... 5 QRP20 Circuit Description ............. 7 Block Diagram ................................ 8 Parts List ........................................ 9 Schematic Diagram ...................... 10 Parts Layout Diagram .................. 11 QRP20 Assembly Instructions .....
INTRODUCTION: Most "QRP" transmitters are one-of-a-kind experimental circuits which take some patience and fine-tuning to get clean keying and satisfactory performance. Most QRP building projects presume either unlimited radio junkboxes with all the right coils and capacitors, or that you have a lot of time on your hands to track down needed parts. And that is part of what ham radio can be all about.
If you're studying this manual before deciding to try this Ramsey "QRP" transmitter project, perhaps the following discussion will be helpful to you. The purpose of this manual is to help you construct this Ramsey Electronics 4stage, variable-frequency CW transmitter efficiently and successfully, not necessarily to "sell" you on the merits and fun that have been discovered in ham QRP operation.
start at the proverbial "30 db. over S-9" and work itself down to S-1 for reasons that will become obvious. S9+10 db. 1000 watts output S9 100 watts output S8 25 watts output S7 6.25 watts output S6 1.56 watts output S5 .39 watts output We can see that it becomes easy to play games with such numbers. For example, an RST of 439 is a legitimate report which permits reasonably effective communication.
On the other hand, if you hear a 1000 watt station producing a moderate signal such as S4 or S5, you can reasonably assume that you will not have a lot of luck over that path right now with the theoretical S1 signal level of your QRP transmitter. While these figures also can be used to show how nice it is to have a power amplifier and beam antenna, they indeed serve to show that reasonable signal levels indeed are achievable with low power and a dipole antenna.
Q3 is a Class C RF amplifier that amplifies the RF output of Q2 to the final RF power output level. L6,C17 and C18 form a low pass filter (Butterworth) to match the output of Q3 to the antenna and reduce harmonics to acceptable levels as specified by the FCC.
PARTS SUPPLIED WITH QRP20 TRANSMITTER KIT: CAPACITORS: 1 47 pf capacitor (C6) 2 68 pf capacitor (C2,C12) 2 220 pf capacitor (marked 220 or 221) (C17,C18) 1 330 pf capacitor (marked 330 or 331) (C3) 11 .01 uf capacitors (marked .01 or 103 or 10 nf) (C1,4,5,7,8,9,10,13,14,15,19) 1 100 to 220 uf electrolytic capacitor (C16) INDUCTORS: 3 100 uh inductor (looks like a resistor with brown-black-brown-gold or silver bands) (L2,L4,L5) 1 2.
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QRP20 PARTS LAYOUT DIAGRAM: QRP-20 • 11
"LEARN-AS-YOU-BUILD" TRANSMITTER ASSEMBLY STRATEGY: As you can see in examining the circuit board and components, there is a bit more to this transmitter kit than soldering a few parts and putting a signal on the air. So that you don't spend extra time "troubleshooting" instead of getting on the air, we strongly recommend you follow the assembly strategy and step-bystep procedures we are providing.
5. Insert and solder R1, the 10K tuning potentiometer. 6. Insert and solder S1, pushbutton switch. Carefully select, insert and solder the following components in the order given in the following steps. Check off each step as completed. 7. C16, 100 to 220 uf electrolytic. Electrolytic capacitors are polarized, which means there is a right and a wrong way to install them! Generally, the Negative ( - ) side is indicated on the capacitor, while the Positive ( + ) is shown on the PC board.
18. Install R14, 10K ohms [brown-black-orange]. 19. Install Q4, be sure to orient its flat side correctly as shown. 20.Install C15, .01 uf (marked .01 or 103 or 10 nf). So far, here's what we've accomplished. First, we've got over a third of all the parts soldered onto the board, which should make you happy, and you should be used to locating the correct component holes with increasing ease by seeing them in relation to previously installed components.
29. Install C3, 330 pf (marked 330 or 331). 30. Install R6, 470 ohms (yellow-violet-brown). With the above components installed correctly, the three holes for Q1 should be clearly apparent. Make sure Q1 is correctly identified as a 2N3904. 31. Install Q1, 2N3904. Orient its flat side correctly. 32. Install C5, .01 uf 33. Install R7, 100 ohms (brown-black-brown). 34. Install C4, .01 (marked .01 or 103 or 10 nf). 35. Install R5, 10K ohms (brown-black-orange). 36. Install C6, 47 pf.
CRYSTAL OSCILLATOR TESTING: ◊ ◊ ◊ ◊ Connect a key, keyer or momentary switch to J3. Connect +12VDC to power connector J4. Note that the CENTER connection is the positive (+) side. Tune a nearby receiver to the anticipated crystal frequency. Make sure that S1 is set to the correct crystal position. Keying J3 should result in a crisp, clean oscillator signal in your receiver. Adjusting the R1 tuning control should vary the crystal frequency up to 7 KHz.
46. Install C14, .01 uf (marked .01 or 103 or 10 nf). 47. Install C9, .01 uf (marked .01 or 103 or 10 nf). 48. Install D1, 1N4002 (large black epoxy body), notice placement of banded end. 49. Install L4, 100 uh inductor [brown-black-brown-silver]. 50. Install R8, 47K (yellow-violet-orange). 51. Install C7, .01 uf (marked .01 or 103 or 10 nf). 52. Install C12, 68 pf (marked 68 or 68K). 53. Install Q3, 2N3053. Again observe the placement of the tab. 54.
14 to 15 volts DC. The easiest method is to place two fresh "D cells" in series with your power source, if a full 13.6-15 volts DC is not available. If your supply voltage is in the 11-12 volt range, you can expect a 200 to 250 ma current flow and about one-half watt of the RF output power. With a solid 14 to 15 volt supply, you can expect about 400 ma current draw and up to 3/4 watt of RF output power.
Please remember, though, that a flashlight bulb does NOT present the proper load impedance to the transmitter output, so theoretical calculations based on the bulb`s rating can only be approximate. For example, the PR-4 at full brilliance presents only an 8.2 ohm load to the transmitter. If ANY flashlight bulb lights up when connected to the antenna jack of this transmitter, you can be satisfied that you have RF output power ROUGHLY comparable to the DC power rating of the bulb you are using.
is the Ramsey CW-7 CMOS Keyer, with built-in sidetone. This transmitter is an ideal travel companion to the growing number of portable shortwave broadcast receivers which feature digitally synthesized tuning, memories and other features, provided that a BFO for CW-SSB reception is one of the features.
FINAL CONSIDERATIONS: Our earlier discussion of how a watt of RF output can indeed offer satisfying communications has several presuppositions: 1. A resonant antenna (dipole or quarter-wave vertical) 2. Good quality coaxial feedline and connectors 3. An effective earth ground We cannot expect good results from low levels of RF output if the power gets wasted in lousy coax, corroded connections, or poor antennas.
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The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting the factory. Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too! All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual is your assurance that a team of knowledgeable people have field-tested several "copies" of this kit straight from the Ramsey Inventory.
20 METER CW TRANSMITTER KIT Quick Reference Page Guide Introduction to the QRP20 .............. 4 Understanding power levels ........... 5 QRP20 Circuit description .............. 7 Parts list .......................................... 9 Schematic Diagram ...................... 10 Parts layout diagram .................... 11 QRP20 Assembly instructions ...... 12 Initial tests .................................... 17 Options for finishing project .......... 20 Troubleshooting guide ..................
