20 METER (14 MHZ) ALL MODE RECEIVER KIT Ramsey Electronics Model No.
PARTIAL LIST OF AVAILABLE KITS RAMSEY TRANSMITTER KITS • FM10A, FM25B Stereo Transmitters • AM1, AM25 AM Transmitters • TV6 Television Transmitter • FM100B Professional FM Stereo 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 • MX5, MX-10 Mixers • MD3 Microwave Motion Detector • TFM3 Tri-Field Meter • STC1 Stereo Transmitte
Ramsey Publication No. MHR20 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR HR20 AMATEUR RECEIVER KIT TABLE OF CONTENTS Introduction to the HR20 .................4 About Direct Conversion .................5 Circuit description ...........................6 Parts list ..........................................7 Schematic diagram .........................9 Parts layout ...................................10 Assembly instructions ...................11 Initial testing ..................................
INTRODUCTION: If you like plenty of action and DX (long distance) communications, the 20 meter Ham band is the place to be. Almost 24 hours a day there’s something interesting happening on 20 meters. There are several groups of people who will enjoy this Ramsey HR20 Receiver: • Experienced Ham operators who want a simple extra receiver for keeping one ear on 20 meters while doing something else. • Beginners who would like to start by listening in on one of Ham radios most active bands.
This receiver circuit is ideal for discovering just how simple a true “Communications Receiver” can be . That’s right- there is a BIG difference between the Ramsey HR20 and other simple short wave radio circuits we can try to build. Yet it is very easy to build. Our HR-series are by far the easiest to build of all the Ramsey kit receivers and therefore very nice for radio newcomers.
Advantages of any Direct Conversion receiver include: • • It is simple, and therefore economical and easy to build It is quite sensitive even with a simple antenna • Its tuning oscillator could even be set up to serve directly as a transmitter VFO in a simple transceiver setup. A common problem with DC receivers is that they are easily overwhelmed by strong AM broadcast stations from almost anywhere, whether it’s your local rock and roll broadcaster, Radio Moscow or the Voice of America.
PARTS SUPPLIED WITH THE HR20 KIT: CAPACITORS: 1 1 2 4 2 3 15pF ceramic disc capacitor [marked 15 or 15K] (C4) 27pF ceramic disc capacitor [marked 27 or 27K] (C13) 36pF ceramic disc capacitor [marked 36 or 36K] (C1,C2) .01µF disc capacitor [marked 103 or .01 or 10nF] (C3,C5,C6,C7) 4.
"LEARN-AS-YOU-BUILD" RECEIVER ASSEMBLY STRATEGY: To help you learn just what exactly is going on we'll discuss the purpose of most of the components or groups of components as we go along. Since we are trying to keep assembly of the board simple, we will not be able to fully describe each individual component’s function as you build, but Ramsey's "Learn-As-You-Build" kit assembly philosophy still stands. Check off each step as understood and completed.
HR20• 9
HR20 PARTS LAYOUT DIAGRAM HR20• 10
RECEIVER ASSEMBLY: 1. Install the RCA antenna jack, J1. Solder all four points. 2. Install C5, a .01µF ceramic disc signal coupling capacitor . This capacitor brings the signal up to the front of the PC board. Notice the long PC trace from J1 through C5 to R1. 3. Install potentiometer R1, the RF gain control. Insert it into the PC board so that it seats firmly and is straight and even. Solder the three pins and the two mounting tabs. 4. Examine inductor L1.
are marked by polarity and must be installed in the proper direction. You’ll see that one side of the capacitor has a black band and is marked with a ‘-’ sign. This is the negative side, the other side is the positive lead. Make sure you insert the positive lead into the ‘+’ marked hole on the PC board. 12. Install C11, a 100-220µF electrolytic capacitor. Remember to observe correct polarity. C10 and C11 provide voltage stabilizing which directly improves the performance of the SA602 oscillator. 13.
25. Install the 9-volt battery snap connector, making sure that the red (+) and black (-) leads are correctly installed. 26. Install C7, .01µF disc capacitor (marked 103 or .01 or 10nF). 27. Install C8, 4.7-10µF electrolytic capacitor. Observe polarity. 28. Install U2, the LM386 audio amplifier IC chip. Just like the SA602, you must correctly position the notched or banded end. 29. Install R6, 10K ohm resistor (brown-black-orange). 30.
INITIAL TESTING OF YOUR HR20: You’re now ready to power up and test your HR20, but before you begin take some time to sweep off your bench of any loose component leads or solder splashes. A clean work area not only makes testing less frustrating but also less prone to problems.
Alignment: Turn on whatever reference signal source you plan to use. This can be a regular transceiver keying a few milliwatts into a dummy load, a crystal oscillator or a signal generator. Or, you can look for a known signal that you have tuned in on another receiver. If you are without any reference signal whatsoever but have a reasonable antenna , you can use your familiarity with the 20m band to make a rough alignment of the receiver.
USING YOUR RECEIVER: In your first tests, you might feel that tuning in CW and SSB stations by turning the control shaft seems tricky. Don't despair! The addition of a simple knob to the final version of your kit will result in more comfortable tuning right away. Also, the larger the knob, the easier tuning is. Even smoother control can be accomplished by a vernier dial, which will also provide calibration marks.
SA602 audio output at the volume control, and switch in a pleasant oscillator pitch (keying sidetone) which is amplified to listening level by LM386. The Ramsey Electronics Universal timer kit No. UT-5 is easily adapted as a sidetone oscillator. • SPEAKER OPERATION A fifty cent, two inch diameter speaker, lying naked on your workbench will give you a fair test of the speaker output capability.
• MORE AUDIO POWER - ANOTHER WAY If you want to use your HR20 for casual band monitoring while you are busy across the room, in the shop, to share with a class or club or group and want LOTS more volume, try building up our very inexpensive Ramsey BN-9, 2 watt general purpose amplifier kit. Supply DC voltage to such an amplifier separately, using D-cells, a lantern or auto battery , or a well filtered power supply.
TROUBLESHOOTING TIPS: PROBLEM: ALL signals are chirpy and unstable. SOLUTION: Sorry to have to say it , but this condition is only caused by a weak battery! Use a fresh alkaline cell. Any strong signal forces the audio circuit to rob voltage from the oscillator, which cause the instability. PROBLEM: Occasionally good but erratic operation. SOLUTION: Check very carefully for a poor solder connection. PROBLEM: Signals have an unpleasant hissing pitch.
GENERAL NOTES FOR EXPERIENCED QRP BUILDERS: We at Ramsey Electronics deliberately designed the HR-series of DC receivers to be easily available, affordable and buildable by any person willing to follow the assembly directions. To achieve this goal, the current models, with direct coupling of the SA602 to the LM386 operating with a gain figure of 50, use an amazing minimum of parts.
BANDSPREAD AND TUNING RANGE: The easiest way to enjoy finer tuning , if you plan to use your receiver only for checking your favorite segment of the band, is to adjust the oscillator coil so that your desired segment falls within the second half of the rotation range of the tuning control. The first half of the rotation range covers about 70% of the actual tuning in KHz, while the other 30% is spread over the other half of the rotation range.
FREQUENCY STABILITY: A kilohertz of drift is not a big deal in FM circuits or a shortwave broadcast configuration, but ANY frequency instability is annoying when trying to receive CW or SSB. The varactor - controlled Local Oscillator is indeed a VFO, and therefore needs all the consideration given to any VFO circuit.
another way of getting bandspread for your favorite frequencies. Finally, it may be necessary to operate the counter on battery power only; connection of an AC adapter might introduce considerable hum into the receiver. THE LM386 AUDIO OUTPUT: As already mentioned the LM386 is certainly capable of far more audio power output than is given in this basic receiver circuit. It can only boost what it gets directly from the SA602.
The ‘-’ side of the new capacitor is connected to the circuit trace leading to the volume control. Mount this capacitor as close to the body of the new LM386 as possible. Keep all leads as short as possible. This modification results in very good speaker volume but will also require closer attention to battery quality and condition or else the audio circuits will cause oscillator instability. Two alkaline cells in parallel or a 12 volt supply are recommended.
CONSTRUCTION NOTES: HR20• 25
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.
3. FACTORY REPAIR OF ASSEMBLED KITS: To qualify for Ramsey Electronics factory repair, kits MUST: 1. NOT be assembled with acid core solder or flux. 2. NOT be modified in any manner. 3. BE returned in fully-assembled form, not partially assembled. 4. BE accompanied by the proper repair fee. No repair will be undertaken until we have received the MINIMUM repair fee (1/2 hour labor) of $25.00, or authorization to charge it to your credit card account. 5.
HR20 AMATEUR RECEIVER KIT Quick Reference Page Guide Introduction to the HR20 ................ 4 Circuit description ........................... 6 Parts list ......................................... 7 Schematic diagram ........................ 9 Parts layout .................................. 10 Assembly instructions .................. 11 Initial testing ................................. 14 Alignment ..................................... 15 Troubleshooting guide .................. 19 Warranty..............
