Ramsey Electronics Radio SR2 User Guide

4-19.5 MHz  
SHORTWAVE RADIO  
Ramsey Electronics Model No.  
SR2  
Have you ever wanted to get into the fascinating world of radio?  
The Ramsey SR2 is a fine performer that will bring in the world  
using just a few feet of wire as an antenna! Folks of all ages  
have successfully built and enjoyed this easy and fun kit.  
Enjoy hours of fascinating international listening using just a simple  
indoor wire antenna  
Select portions of the 4 to 19.5 MHz shortwave band, easily re-tuned at  
any time  
Smooth varactor diode tuning  
Excellent sensitivity and selectivity  
Front panel Volume and Tuning controls  
Multi-stage audio amplifier for room filling volume  
Well designed superhetrodyne circuit is easy to build, makes a nice  
one-evening project  
Ideal scout, school, or club project  
Clear, concise step-by-step instructions carefully guide you to a  
finished kit that not only works - but you’ll also learn too!  
Runs on a standard 9 volt battery  
Add our matching case and knob set for a finished ‘pro’ look  
 
Ramsey Publication No. MSR2  
Manual Price Only: $5.00  
KIT ASSEMBLY  
AND INSTRUCTION MANUAL FOR  
4-19.5MHz  
SHORTWAVE RADIO  
TABLE OF CONTENTS  
Introduction to the SR2........................................ 4  
What You Can Expect to Hear............................. 4  
Shortwave Listening as a Hobby ......................... 5  
Circuit Description................................................ 6  
Parts Layout Diagram .......................................... 8  
Block Diagram ..................................................... 9  
Parts List.............................................................. 10  
Assembly Instructions.......................................... 12  
Schematic Diagram ............................................. 14  
Shortwave Antenna Ideas.................................... 20  
Initial Testing and Adjustment............................. 21  
Troubleshooting Tips ........................................... 23  
Ramsey Kit Warranty........................................... 27  
SR2 3  
 
INTRODUCTION TO THE SR2  
The SR2 is a single-conversion superheterodyne receiver designed  
specifically for listening to AM broadcasting stations in the range of 4 to 19.5  
MHz. Because of this "superhet" design, your favorite foreign broadcasting  
services will come in loud and clear, with pleasing audio sound quality, with  
a minimum of overload, frequency drift or heterodyne whistles. Because of  
this broadcast oriented design, other shortwave signals such as Morse code  
(CW), single-sideband (SSB) voice communications and some Teletype  
signals will usually sound like garbled hisses. On the other hand, similarly  
inexpensive receivers designed for CW and SSB can give only marginal  
performance in receiving broadcast stations due to the lack of  
superheterodyne design. For example, our popular Ramsey direct-  
conversion receivers for the 40,30 and 20 Meter Amateur bands will also  
pick up AM broadcast stations, but you'll mainly hear their strong AM  
"carrier" signal due to the lack of the superheterodyne circuitry. Even if such  
a carrier is tuned to a "null," listening fidelity is less than desirable.  
WHAT YOU CAN EXPECT TO HEAR  
First, let's take a look at what is POSSIBLE to hear on your SR2. The  
following are the international shortwave broadcasting bands within its  
tuning range:  
4.750-5.060 MHz. (Lower power, regional "tropical" broadcasting)  
5.950-6.200 MHz (Late evening)  
7.100-7.300 MHz. (Late afternoon, early evening) (This band is always  
shared with the 7.0-7.3 MHz Amateur Radio Band)  
9.500-19.500 MHz. (Always "something" on, 24 hours a day!)  
Especially strong signals include these, among others:  
SR2 4  
 
BBC London: an intelligent perspective on world affairs  
Radio Canada International: editorial quality similar to BBC  
Radio Moscow: powerful signals, increasingly honest and open  
Voice of America: VOA broadcasts are "aimed" outside the USA, but if  
you're in the "path" you'll hear it loud and clear!  
U.S. Armed Forces Radio-TV "Feed" Service: Master programming  
source for U.S. military radio- hear CBS-NBC-ABC-Mutual news all on  
the same "channel," plus many other features and spots which give a  
feel for how it's going with those in uniform  
Numerous South American stations  
USA religious broadcasting to other continents  
You'll easily tune in broadcasts from many other countries as well. As you  
become more and more familiar with the world of shortwave broadcasting,  
you'll be deciding on your own favorite band.  
You will hear a variety of other "interesting" sounds, but just remember that  
this receiver is designed for AM only. If a Morse Code signal really sounds  
"good," it is because it is being transmitted in AM tone-modulated form, or  
perhaps the signal is so close to an AM broadcast carrier that the carrier  
acts as a "beat-frequency-oscillator" (BFO). Even though this receiver can  
let you tune through several different HAM radio bands, the signals are not  
likely to be intelligible. Reception of CW and SSB signals on an AM receiver  
requires a BFO. This is not a complicated feature, but it is beyond the  
purpose of the SR2. Our companion receivers designed for the HAM bands  
will let you tune into these SSB and CW broadcasts.  
SHORTWAVE LISTENING AS A HOBBY  
Many people worldwide enjoy listening to shortwave broadcasts of all kinds,  
and they keep written records of what they hear. Almost every nation on  
earth has some sort of shortwave broadcast service, though many are  
much more challenging to tune than the powerful signals of Radio Moscow  
and the BBC. In addition, these "SWLs" (Shortwave Listeners) listen to HAM  
operators, government and commercial stations and even clandestine  
operations. Some shortwave listeners enjoy collecting QSL cards from  
stations which they have logged. Shortwave listening is, for some, a step  
toward getting a HAM radio license. For others, it is a great hobby in itself.  
The SR2 Shortwave Receiver is a good introductory receiver for this hobby.  
After you decide exactly what kinds of listening are of the most interest to  
SR2 5  
 
you, you'll be in a better position to choose a more elaborate receiver. While  
there are various multi-band portable radios available, you can expect to pay  
at least $100 for a receiver offering a significant improvement over your  
trusty SR2.  
To learn more about this SWL hobby, look for a copy of "Popular  
Communications" at newsstands. An inexpensive and interesting general  
introduction to all kinds of radio listening is the book, "Shortwave Listening  
Guide" by William Barded, Jr. (1987; Radio Shack Catalog Number 62-  
1084). This book also includes helpful introductory information about VHF  
monitoring, which you can enjoy with the Ramsey FR-146 and AR-1 receiver  
kits, as well as HAM radio, CB, antennas, and other topics.  
To learn more about Ramsey Electronics HAM radio kits, write for our  
complete catalog. (And, be sure to tell us how you're doing with your SR2  
Receiver!) To learn more about the hobby of HAM radio, write ARRL  
(American Radio Relay League), 225 Main Street, Newington, CT 06111 or  
CIRCUIT DESCRIPTION  
The following paragraphs describe the circuit operation of the SR-2  
Shortwave Receiver kit. Through the use of a simplified block diagram the  
basic circuit theory is easy to understand. The full schematic (pg. 14) shows  
the details concerning specific operation and component variable  
configurations.  
Take a moment and examine the circuit block diagram found on page 9. The  
simplified signal flow of the block diagram shows the basic sections of the  
receiver. The corresponding components are noted under each main block  
and can be cross referenced to the schematic  
The start of our circuit begins with the Antenna. RF Signals (Fc = carrier  
frequency) from the Antenna are applied to the RF Input and Filtering  
allowing only the signals of interest to pass through. The high pass filter  
helps eliminate unwanted signals picked up by the antenna improving the  
overall reception quality of the radio.  
After the input signal is filtered, it moves to the Mixer stage. Notice on the  
diagram that there are two inputs to the mixer. We have discussed one of  
these input signals coming into the mixer but not the other as of yet. Drop  
down to the Local Oscillator block. The local oscillator (LO for short) acts as  
your tuning control for what frequencies you can receive by generating a  
signal on the board close in value to that which will be used by the mixer.  
There is a direct relationship between the generated frequency of the local  
oscillator (LO) and the exact receive frequency (Fc) you want to listen to.  
This will become clear when we finish discussing the block diagram.  
The LO section is a Colpitts oscillator that takes advantage of smooth  
SR2 6  
 
varactor diode tuning. The varactor (D3) forms an L/C (Inductor/Capacitor)  
tank circuit with T3. Increasing the voltage on the varactor diode with R21  
(Tuning Pot) increases the capacitance of D3 thus increasing the frequency  
output of the LO section.  
Now that we know the two signals coming into the Mixer stage, both the Fc  
(receive carrier frequency) and the LO (generated local oscillator), we can  
better cover its operation. The mixer takes these input signals and performs  
a few very basic operations. The technical explanation of how the mixer  
combines these signals through Fourier Series is interesting but very drawn  
out. The point of using the block diagram, however, is to simplify matters.  
Therefore, the function of the mixer is to obtain the ‘product’ and the ‘sum’ of  
the input signals. This means you take the input signals and merely ‘add’  
and ‘subtract’ their values to determine what you get on the output. The  
general formulas to use are quite simply, ‘Fc + LO = Mixer Output’ and ‘Fc –  
LO = Mixer Output’.  
The realistic output of the mixer stage unfortunately has other signals  
besides the ones we want. This brings us to the next stage, Intermediate  
Frequency Filtering. An Intermediate Frequency (IF) is a signal somewhere  
between the RF signal Fc we started with and the final audio message we  
are trying to get. The desired IF we are dealing with is a fixed number, such  
as 455 kHz. As long as the proper relationship between Fc and the LO  
exists, the IF value will stay constant. Due to the fact that the IF frequency  
stays the same all the time, the Intermediate Frequency Filter can be very  
narrow. The filter will remove any other signals coming from the mixer that  
are not in the proper pass band and yield a clean signal for further  
processing.  
The next stage is an Amplifier with an adjustable gain feedback loop. The  
gain control is dependant on the amount of signal being received (this  
Automatic Gain Control ‘AGC’ will be covered in a moment). The amplifier  
boosts the signal level of the incoming IF and gives us a stronger signal to  
work with.  
After the amplifier stage is another Intermediate Frequency Filter. This helps  
remove any unwanted residual signals still present and cleans up the  
amplified IF for a high quality signal.  
At this point the audio signal we are trying to obtain is riding on the IF signal.  
The Demodulator circuit finally extracts the message from the IF through a  
process called envelope detection. Now that we have our message back in  
the audio realm, it is directed through the audio circuitry to the speaker  
output.  
Wait, there are still a few sections we have not discussed!  
The demodulated audio branches off before the audio circuitry and is used  
to perform some useful functions. The RSSI LED, Received Signal Strength  
Indicator Light Emitting Diode, gives us a general signal level feature. The  
stronger the signal we receive, the brighter the LED will glow. This is great  
for help pulling in those weak transglobal transmitter signals. The gain of the  
SR2 7  
 
RSSI circuit is controlled by the value the feedback resistor R17. If you are  
commonly using a small antenna and listening to weak signals, increase the  
value of R17 to customize the response indication of D2, the signal strength  
LED.  
The final stage, and the real secret to the sensitivity of the receiver, is the  
Automatic Gain Control (AGC). The gain control looks at the amount of  
signal level present at the output of the demodulator and varies the amount  
of gain the Amplifier has accordingly. If there is a strong signal coming  
through the demodulator the AGC circuit lowers the gain of the amplifier. If  
the receive signal coming through the demodulator is very weak, the AGC  
circuit increases the gain of the amplifier (Q2) allowing us to receive signals  
from around the world and listen to them with clarity.  
SR2 PARTS LAYOUT DIAGRAM  
SR2 8  
 
SR2 9  
 
PARTS LIST  
CAPACITORS  
ˆ 1 10 pF ceramic disc capacitor [marked 10] (C30)  
ˆ 1 47 pF ceramic disc capacitor [marked 47] (C15*)  
ˆ 4 100 pF disc capacitor [marked 100, 101, or 100K] (C5,15*,16*,17)  
ˆ 1 330pF disc capacitor [marked 330 or 331] (C2)  
ˆ 6 .001µF disc capacitors [marked .001, 102, or 1nF]  
(C1,3,16*,20,21,25)  
ˆ 1 .0039 uF disc capacitor [marked 392 or 392K] (C31)  
ˆ 4 .01µF disc capacitors [marked .01, 103, or 10nF] (C4,6,8,28)  
ˆ 6 .1µF ceramic disc capacitor [marked .1 or 104] (C7,10,12,18,19,29)  
ˆ 2 1µF electrolytic capacitors (C9,24)  
ˆ 3 10µF electrolytic capacitors (C11,22,23)  
ˆ 2 220µF electrolytic capacitors (C13,14)  
ˆ 1 1000 µF electrolytic capacitor (C26)  
INDUCTORS  
ˆ 2 1 µH inductors [looks like a resistor with brown-black-gold bands]  
(L1,L2)  
ˆ 1 12 µH inductor [looks like a resistor with brown-red-black bands]  
(L3)  
ˆ 2 Shielded can inductors [marked 42IF-103] (T1,2)  
ˆ 1 Shielded can inductors [marked 42IF-123] (T3)  
RESISTORS  
ˆ 1 2 ohm [red-black-gold] (R15)  
ˆ 1 100 ohm [brown-black-brown] (R26)  
ˆ 3 270 ohm [red-violet-brown] (R16,22,25)  
ˆ 8 1K ohm [brown-black-red] (R3,7,9,10,13,17,18,24)  
ˆ 5 10K ohm [brown-black-orange] (R6,8,11,19,23)  
ˆ 2 22K ohm [red-red-orange] (R2,4)  
ˆ 3 100K ohm [brown-black-yellow] (R1,5,20)  
ˆ 1 1M ohm [brown-black-green] (R12)  
SEMICONDUCTORS  
ˆ 1 Red LED (D2)  
ˆ 1 1N270 diode, glass bead style (D1)  
ˆ 1 Varactor diode, transistor style body with two leads (MVAM108) (D3)  
ˆ 3 NPN transistors, 2N3904 or similar (Q1,2,3)  
ˆ 1 LM358 8-pin DIP IC (U1)  
ˆ 1 LM386 8-pin DIP IC (U2)  
SR2 10  
 
HARDWARE AND MISCELLANEOUS  
ˆ 1 SR2 printed circuit board  
ˆ 2 10K potentiometers (R14,21)  
ˆ 1 DPDT PC-mount push button switch (S1)  
ˆ 1 RCA-type PC-mount jack (J1)  
ˆ 1 Subminiature phone jack (J2)  
ˆ 1 9-volt battery snap connector  
ˆ 1 9-volt battery hold-down clamp  
REQUIRED, NOT SUPPLIED:  
ˆ 9-volt alkaline or heavy-duty battery  
ˆ Earphone, small speaker, or external amplifier with speaker  
ˆ Antenna or suitable cable, connector, grounding  
OPTIONAL  
Ramsey SR2 case and knob set (CSR), or your own enclosure  
SR2 11  
 
ASSEMBLY INSTRUCTIONS  
In ALL PC-board assembly steps, our word "INSTALL" means to do this:  
ˆ Insert the part, oriented or "pointed" correctly, into its holes in the PC  
board.  
ˆ 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 circuit board.  
ˆ Solder ALL wires or pins of the part.  
ˆ Trim or "nip" all excess wire lengths extending beyond each solder  
connection, taking care that wire trimmings do not become lodged in  
solder connections.  
You can see that this circuit board, the center portion in particular, is fairly  
well-filled with components. There's more to this receiver than the average  
beginner's radio or even our popular Amateur Band receivers.  
Follow the assembly instructions IN SEQUENCE and check off each step as  
understood and completed. Some of the components require modification!  
Examine the schematic circuit diagram and PC Board parts layout diagram  
as you proceed.  
Use good soldering techniques! Let your soldering iron tip heat both the  
component lead wire and PC board trace enough so that the wire itself AND  
the foil trace BOTH become hot enough TOGETHER to melt a bit of solder  
so that it flows smoothly from the pin to the PC board trace.  
Enough said... Let’s get building!  
ˆ 1. Install S1, the DPDT push button switch. Ensure that the white  
plastic switch extends out over the edge of the PC board and that the  
switch is flush to the board. Solder all six pins.  
ˆ 2. Install one of the 10K PC mount potentiometers, R14. Be sure it is  
seated flush to the PC board, then solder all 5 pins.  
ˆ 3. Install the other 10K PC mount pot, R21. Take care to seat it  
properly before soldering the 5 pins.  
ˆ 4. Install J1, the RCA jack. You will want to check your placement  
before soldering and be sure to solder all 4 tabs.  
SR2 12  
 
We will now begin constructing the local oscillator section.  
ˆ 5. Install C22, one of the 10µF electrolytic capacitors. Electrolytic  
capacitors have a right and wrong way to be installed. Usually,  
capacitors have a wide stripe which indicates their negative lead and the  
PC board or Parts Layout Diagram will show the positive side of the  
capacitor's installation hole. Be sure to place the ( + ) capacitor lead  
into the PC board ( + ) hole and the ( - ) lead into the ( - ) hole before  
soldering.  
ˆ 6. Install D3, the varactor diode, marked MVAM108. This part looks  
like a transistor except that it only has two leads. It must be installed  
with the proper polarity to work correctly. You will note that it has a flat  
side. Be sure to look at the PC board silkscreen or parts layout diagram  
for proper placement of the flat side. Once you have correctly placed  
the part, solder the leads.  
ˆ 7. Install R23, 10K ohm [brown-black-orange].  
ˆ 8. Install Q3, an NPN transistor, [marked 2N3904]. This part is also  
oriented by the flat side so check your parts layout diagram for proper  
placement. Bend the center lead out until it fits in the board and seat  
the part as close to the PC board as possible. Solder all three leads.  
ˆ 9. Install C17, a 100 pF capacitor [marked 100, 101, or 100K].  
ˆ 10. Install C25, .001µF disc capacitor [marked .001, 102, or 1nF].  
ˆ 11. Install C19, a .1µF ceramic disc capacitor [marked .1 or 104].  
ˆ 12. Install C18, another .1µF ceramic disc capacitor [marked .1 or 104].  
ˆ 13. Install R20, 100K ohms [brown-black-yellow].  
ˆ 14. Install R25, a 270 ohm resistor [red-violet-brown].  
ˆ 15. Install R19, 10K ohms [brown-black-orange].  
ˆ 16. Install R24, 1K ohms [brown-black-red].  
ˆ 17. Install C26, the 1000µF electrolytic capacitor. Remember to check  
the polarity and install properly before soldering.  
ˆ 18. Install R22, 270 ohms [red-violet-brown].  
ˆ 19. Install C20, .001µF disc capacitor [marked .001, 102, or 1nF].  
ˆ 20. Install C21, another .001µF disc capacitor [marked .001, 102, or  
1nF].  
Before installing T3, the shielded can inductor [marked 42IF123] we must  
make a modification to the part. It's time for a little "destruction"! (If you  
SR2 13  
 
SR2 14  
 
SR2 15  
 
jumped ahead and installed T3, we've got bad news for you). Before this  
shielded transformer can be installed, its internal capacitor needs to be  
removed. Looking at the underside of this transformer, you'll see a tubular  
part, probably white with a brown band, somewhat like the resistors in this  
kit. This is brittle and easily crushed with any sharp object that can be  
pressed against it with mild force (small nail, nutpick, small screwdriver).  
You'll find this capacitor will easily disintegrate into particles. DO NOT crush  
the capacitors in the other two inductors!  
ˆ 21. After crushing the internal capacitor, install T3. The part fits in the  
board only one way. Solder all pins.  
That completes assembly of the local oscillator section except for two parts.  
You may notice that we skipped over C15 and C16 while installing the other  
parts in the area. The reason is that you will have to decide the frequency  
range you’re trying to receive to know what value capacitors to install. We’ll  
leave that until the end of the assembly process.  
We’ll now move on to the RF section of your SR2 kit. The next few parts  
form an input filter and mixer section, to combine the RF input with the L.O.  
section just built. The output of the mixer is the IF, from which we’ll extract  
the final audio. But let’s not get ahead of ourselves.  
ˆ 22. Install L1, 1µH inductor [looks like a fat resistor with brown-black-  
gold bands].  
ˆ 23. Install L2, the other 1µH inductor [looks like a fat resistor with  
brown-black-gold bands].  
ˆ 24. Install C3, .001µF disc capacitor [marked .001, 102, or 1nF].  
ˆ 25. Install C2, 330 pF disc capacitor [marked 330 or 331].  
ˆ 26. Install C1, .001µF disc capacitor [marked .001, 102, or 1nF].  
ˆ 27. Install R13, 1K ohms [brown-black-red]. R13 isn’t part of the RF  
section but is easier to install now, while we’re in the area.  
ˆ 28. Install R3, 1K ohm [brown-black-red]. Watch that third color band  
as red is easily confused with orange!  
ˆ 29. Install Q1, another of the NPN transistors [marked 3904]. Observe  
correct orientation of the flat side when placing this part.  
ˆ 30. Install C10, .1µF ceramic disc capacitor [marked .1 or 104].  
ˆ 31. Install R12, 1M ohm [brown-black-green]. C10 and R12 are part of  
the bias circuit for the audio amplifier, U1. Like R13, it is easier to install  
these parts now.  
ˆ 32. Install C30, 10pF [marked 10].  
SR2 16  
 
ˆ 33. Install R2, 22K ohms [red-red-orange].  
ˆ 34. Install R1, 100K ohms [brown-black-yellow].  
ˆ 35. Install C24, 1µF electrolytic capacitor. Remember to watch polarity  
when installing.  
ˆ 36. Install C5, 100 pF disc capacitor [marked 100, 101, or 100K].  
ˆ 37. Install C4, .01µF disc capacitor [marked .01, 103, or 10nF].  
ˆ 38. Install R26, 100 ohms [brown-black-brown].  
ˆ 39. Install C23, 10 µF electrolytic. Remember to check the polarity  
before installing.  
ˆ 40. Install Q2, the last 3904 transistor. Check the parts placement  
diagram for correct orientation, then install and solder the three leads.  
ˆ 41. Install C6, .01µF disc capacitor [marked .01, 103, or 10nF].  
ˆ 42. Install R4, 22K ohm [red-red-orange].  
ˆ 43. Install T1, one of the shielded can inductors [marked 42IF-103].  
ˆ 44. Install R5, 100K ohm [brown-black-yellow].  
ˆ 45. Install R6, 10K ohm [brown-black-orange].  
ˆ 46. Install C28, .01µF disc capacitor [marked .01, 103, or 10nF].  
ˆ 47. Install C7, .1µF ceramic disc capacitor [marked .1 or 104].  
ˆ 48. Install R7, 1K ohm [brown-black-red].  
ˆ 49. Install C31, .0039 uF disc capacitor [marked 392 or 392K].  
ˆ 50. Install R8, 10K ohm [brown-black-orange].  
ˆ 51. Install C8, .01µF disc capacitor [marked .01, 103, or 10nF].  
ˆ 52. Install D1, 1N270 glass bead style diode. The banded end (cathode)  
MUST be oriented as shown on parts layout.  
ˆ 53. Install R11, 10K ohm [brown-black-orange].  
ˆ 54. Install R10, 1K ohm [brown-black-red].  
ˆ 55. Install R9, 1K ohm [brown-black-red].  
ˆ 56. Install T2, the other shielded can inductors [marked 42IF-103].  
ˆ 57. Install L3, 12 µH inductor [looks like a fat resistor with brown-red-  
black bands].  
SR2 17  
 
ˆ 58. Install C9, 1µF electrolytic capacitor. Check polarity when installing.  
ˆ 59. Install C11, 10 µF electrolytic. Observe correct polarity before  
installing.  
ˆ 60. Install R16, 270 ohm [red-violet-brown].  
PROGRESS SUMMARY  
Now is a good time to take a break. Examine your work so far checking  
things such as component values, parts placement, and solder connections.  
Remember the old adage “The bigger the glob the better the job” does not  
hold true with RF electronics!  
To this point, we have assembled a majority of the receiver. The RF, LO, IF  
and Demodulator sections have been built leaving us with the final audio  
stage, RSSI circuit, and AGC circuit. Sound like a lot more work? Not at all;  
we are going to take advantage of today’s power packed ICs! The LM386  
audio chip takes care of our audio needs while the LM358 opamp is used  
two-fold in the RSSI and AGC circuits!  
ˆ 61. Install C29, .1µF ceramic disc capacitor [marked .1 or 104].  
ˆ 62. Install U1, the LM358 8 pin IC. Do not confuse it with the other IC;  
read the chip marking carefully. You will notice a notch, band or dot on  
one end of the IC. This should be oriented as shown on the parts layout  
diagram and PC board silkscreen. Be sure the part is seated close to  
the PC board before soldering all 8 pins.  
ˆ 63. Install R17, 1K ohm [brown-black-red].  
ˆ 64. Install R18, also 1K ohm [brown-black-red]..  
ˆ 65. Install J2, the subminiature speaker-headphone jack.  
ˆ 66. Install C12, .1µF ceramic disc capacitor [marked .1 or 104].  
ˆ 67. Install R15, 2 ohms [red-black-gold].  
ˆ 68. Next, install U2, the LM386 audio amplifier IC. As with U1, orient  
the notched or dotted end as shown in the parts layout diagram and on  
the PC board silkscreen. Solder all 8 pins.  
ˆ 69. Install C14, 220µF electrolytic capacitor. The positive lead of the  
capacitor must be placed in the hole next to the ( + ) sign.In the same  
way,  
ˆ 70. Install C13, placing the positive lead in the correct PC board hole.  
Remember, the banded side indicates the negative lead.  
71.  
Install the 9-volt battery snap connector, making  
sure that the red ( + ) black ( - ) leads are inserted correctly.  
SR2 18  
 
ˆ 72. Install the battery clamp. Position battery and holder so as not to  
cover nearby PC board mounting holes. Use the method for securing the  
clamp that is most convenient for you, such as:  
wire looped through clamp and PC board holes, soldered.  
small screws  
double-faced adhesive strips  
hot-melt glue  
ˆ 73. If you desire increased audio output, C27, 10 µF, may be installed.  
Be sure the (+) and (-) leads are inserted correctly.  
ˆ 74. We’re at the end now, just one part left to install. Install D2, the red  
LED signal indicator. The short lead is the cathode; it goes toward  
potentiometer R21. Leave it standing about 1/2 an inch off of the board  
when soldering. After soldering bend it over to a 90º angle at its midpoint  
so that it faces the outside of the board.  
Your shortwave broadcast receiver is now finished, except for the capacitors  
that will determine the frequency range you will receive.  
SHORTWAVE ANTENNA IDEAS  
The type of antenna you'll want to use for your SR2 depends on the degree  
of interest you have in shortwave listening, whether you are limited to an  
indoor or balcony antenna, and whether you think you may soon want to  
obtain a HAM radio license. If the latter is true, you may want to consult  
HAM radio literature and build the dipole or vertical antenna which you also  
plan to use for HAM listening and transmitting. A 40-meter (7 MHz) antenna  
is quite nice for the tuning range of the SR2.  
The rest of these notes on antennas are for the benefit of SR2 builders who  
simply wish to enjoy some shortwave broadcast listening. The SR2 is very  
sensitive, so its antenna requirements are minimal for casual evening  
listening when international broadcast signals are quite strong. 10 to 20 feet  
of insulated hookup wire can be neatly strung behind furniture and curtains  
for an adequate indoor antenna. The same length of wire, or more, outdoors  
or up in the attic, will be an even better receiving antenna.  
1. The ideal antenna setup for this frequency range is considered to be an  
outdoor wire 25 to 50 feet in length, with the ground side of the  
antenna jack connected to a copper cold water pipe.  
2. For convenience, a short length of audio cable with pre-wired RCA plug is  
adequate for making antenna and ground connections. (RF coaxial  
cable is not essential for this application).  
3. A "banana plug" may also be plugged into the antenna jack but will not  
SR2 19  
 
provide a ground connection.  
4. If an indoor antenna is necessary, simply make it as long as possible and  
as high up from concrete floors as you can.  
5. When installing any outdoor antenna, BE VERY CAREFUL not to let your  
antenna wire come in contact with electric power lines.  
6. Any antenna wire for shortwave listening may run horizontally, vertically  
or some both ways, or at an angle!  
7. If you have a roof-mounted TV antenna, its feedline will make a great  
antenna for your SR2.  
8. Some existing objects such as; metal downspouts, gutters, windows, door  
screens, or attic insulation foil can serve as antennas!  
If you are completely restricted to indoor antennas, you will enjoy the extra  
boost of the Ramsey Active Antenna Kit, model AA-7. Its built-in whip  
antenna can also be boosted by your simple indoor wire antenna, and the  
AA-7 may be used with any receiver or even a VHF scanner. It's easy to  
build and a nice companion for your SR2. If you need more construction  
details on antennas, check the book mentioned on page 6, or any  
introductory HAM radio book, or the Radio Shack book on Antennas (No.  
62-1083).  
ˆ 75. Decide what frequency range you would like to receive and select  
the values for C15 and C16 from the chart. A suggested configuration  
would be C15 = 47 pF and C16 = 100 pF. This will give you complete  
coverage from 6 to 11 MHz by adjusting T3 in or out. This is a very  
active section of the Shortwave Band and will provide you with hours of  
listening enjoyment any time of the day. Select and install C15 and C16.  
INITIAL TESTING AND ADJUSTMENT  
Before turning on your receiver, please double check the following:  
ˆ correct orientation of all IC's.  
ˆ correct orientation of flat side of all transistors.  
ˆ correct orientation of the diodes.  
ˆ correct polarity of all electrolytic capacitors.  
ˆ 1. Connect a speaker or earphones and antenna.  
ˆ 2. Install a fresh 9-volt alkaline battery.  
ˆ 3. Set both potentiometer controls to their middle positions.  
SR2 20  
 
ˆ 4. Turn ON the receiver.  
After adjusting the volume to a pleasant level, you should hear some  
shortwave stations by turning the Tune Control, no matter how any of the  
adjustable coils happen to be set.  
While listening to any kind of station, whether broadcast or Teletype, etc.,  
use a small screwdriver to adjust the slugs in transformers T1 and T2 for the  
best-sounding reception.  
The Tuning Control covers varying segments of the bands selected by  
adjustment of oscillator coil T3. Adjustment of T3 anywhere between the full  
In  
C16 = .001  
T3 Slug In  
T3 Slug Out  
C15 = None  
C15 = 47 pF  
C15 = 100 pF  
6.5—13.0 MHz  
5.1—7.9 MHz  
4.3—5.3 MHz  
9.0—18.3 MHz  
7.1—10.7 MHz  
6.0—8.3 MHz  
C16 = 100 pF  
C15 = None  
C15 = 47 pF  
C15 = 100 pF  
T3 Slug In  
T3 Slug Out  
8.4—14.2 MHz  
6.0—8.1 MHz  
4.9—6.3 MHz  
11.5—19.5 MHz  
8.5—11.0 MHz  
6.7—8.4 MHz  
position to the full Out position will give the user full range between the  
minimum and maximum frequency coverage set by C15 and C16.  
Both T1 and T2 must be adjusted with a non-metallic alignment tool such as  
is used in radio-TV service. If you do not have one, a suitable tool can be  
made by patiently sanding a screwdriver-like blade on the end of a wooden  
match stick, kabob skewer or small plastic crochet needle. Again, please be  
aware that a metal screwdriver blade will drastically increase the coil  
inductance and make adjustment quite difficult. T1 and T2 are simply  
adjusted for strongest reception of any signal range that is tuned in.  
If you are without any kind of testing or frequency reference equipment  
whatsoever, the easiest way to start enjoying your SR2 is, with the Tune  
control set at its midpoint, slowly tune T3 with your alignment tool as though  
it were a tuning dial. Stop when you come into the middle of a group or  
cluster of foreign broadcast stations. Try tuning around these stations with  
the Tune control. If you like what you hear, readjust both T1 and T2 for best  
SR2 21  
 
reception. Eventually, you will get a clue as to what general frequency band  
you are hearing, because many stations periodically announce their  
frequencies, particularly at sign-on and sign-off times.  
If you like precision, use a frequency counter or calibrated receiver to find  
the SR2's strong oscillator signal, remembering that there is a 455 KHz IF  
difference (above or below) between the local oscillator frequency and the  
broadcast signal you are hearing.  
TROUBLESHOOTING TIPS  
If you experience difficulty, think of your SR2 in its several sections or  
stages: oscillator-mixer, IF audio and AGC, and final audio output (LM386).  
The first step in case of problems is to make sure that the tunable oscillator  
is working, which can be done by listening for its signal on another receiver.  
After the oscillator circuit is confirmed working, standard signal tracing  
procedures should isolate any problem, which will be either an incorrectly-  
installed part, a defective part or a bad solder connection. Correct  
orientation or polarity of all diodes, transistors, electrolytic capacitors and  
ICs is essential.  
PROBLEM: Strong shortwave broadcast audible throughout tuning range  
SOLUTION: This can occur if your antenna is "too good" or if the RF Gain  
control is turned up too high. The high sensitivity of the front end is designed  
for simple antennas, with most reception quite satisfactory with only 25 feet  
or so of wire.  
PROBLEM: Local AM radio station audible throughout tuning range  
SOLUTION: Whether this will even happen depends on how close you are  
to a local AM station. It is very important that all component leads be as  
short as possible, since just a bit of wire can help D1 and the several stages  
of audio amplification give you a free, unwanted "classic crystal radio". A  
grounded metal case for the SR2 is one possible solution.  
SR2 22  
 
THE RAMSEY ELECTRONICS CASE, KNOB & HARDWARE OPTION  
Your finished receiver can be installed in a variety of enclosures of your own  
design and choosing. You might be planning to combine several Ramsey  
circuit kit boards in a single enclosure. Use of the inexpensive and attractive  
Ramsey case and knob kit will give your unit that finished look and increase  
its resale value. These sturdy black instrument cases are supplied with  
neatly lettered front and rear panels, knobs, rubber feet and mounting  
screws.  
OTHER ENCLOSURE RECOMMENDATIONS  
While we believe that the Ramsey enclosure and knob option is a fine value  
for finishing off your Ramsey receiver or transmitter, we are happy to give  
you a couple of additional suggestions and our reasons for them. If your first  
goal is economy and rugged portability, you will find that the circuit board  
can be mounted nicely in a standard VHS videotape storage box, which also  
gives room for a speaker, or earphone storage, and even a roll of antenna  
wire. The controls are easily mounted at one end of such a box. It may be  
necessary to cut away the molded posts which secure the tape cassette  
itself. These storage boxes come in several styles, so pick one which looks  
truly practical as a project enclosure.  
To accomplish RF shielding, the most economical metal enclosure nicely  
suited for Ramsey kit boards is Radio Shack No. 270-253A. This metal utility  
cabinet can accommodate both a receiver and our AA-7 Active Antenna,  
plus speaker, with room for various refinements you might like to add, such  
as power supply or larger battery pack, etc.  
A TUNING DIAL?  
If you use your own enclosure and knobs, you will probably plan some sort  
of dial markings. If you finish your receiver with the Ramsey custom case  
and knob kit, you may wish to copy one of the following designs to make a  
logging scale:  
SR2 23  
 
SAMPLE SHORTWAVE LOGGINGS  
Freq Country  
(MHz)  
Notes/Contributor  
4.30  
4.31  
4.38  
4.40  
4.72  
4.72  
4.78  
4.78  
4.82  
4.82  
4.97  
5.04  
5.50  
5.67  
5.76  
6.01  
6.02  
7.11  
7.12  
7.12  
8.45  
9.02  
9.34  
9.90  
9.90  
9.90  
9.92  
PERU  
DIEGO GA  
PERU  
BOLIVIA  
S VIETNAM  
MYANMAR  
GUATEMALA ID, nx  
MALI  
BOTSWANA lang church svc, choir  
HONDURAS cmtry mx  
UGANDA  
PERU  
ballads, huaynos, brief annmt, TC partial ID, tnx  
oldies, good sig  
long talk, rel talk, choir, poor  
romantic vocals, poor  
VT pop tunes, YL anncr, instl mx  
soft vocals, ID, nx  
FR Spice Girls, Afr pop  
tribal singing, SH talk, ID during nx  
pop mx, ID, phone talk  
flute mx, annmts, nx  
Magnificent 7 song, poss ID  
sports pgm, PSAs  
ETHIOPIA  
PERU  
GUAM AFN  
MEXICO  
Mexico City in SP 1005, U.S. oldies and SP tunes  
UZBEKISTAN mx pgm, ID's, tlk on scientific forum  
THAILAND  
ITALY  
ITALY  
CHINA  
patriotic sounding songs, Asian rock mx,  
ID, mailing QTH, tlk on drug use, mx  
nx in EG re Columbus 2000 project, ID  
V of Russia relay , “Moscow Mailbag”, nx of Russia,  
nx re OPEC, ID, fqy, sked,  
IRAN  
ISRAEL  
BULGARIA  
EGYPT  
RUSSIA  
GERMANY  
Kol Israel  
HB 2142, discussion, US oldies  
Sofia in RS 1840, tlk, regional mx, ID  
EG version of AR poem, chants, ID, garbled audio  
Deut Welle relay Irkutsk, nx, stocks, QTH, ID  
Croatian R relay, UK investm'ts  
11.60 SLOVAKIA  
12.00 UNITED AE  
AWR V of Hope relay ID, relig nx  
AR mx, into EG 0330, nx  
13.64 MADAGASCAR R Canada Int  
13.65 CANADA  
15.14 OMAN  
"Maple Leaf Mailbag  
nx of earthquake in PNG causing tidal wave and local  
damage, MIR space station being closed down, ID,  
mx, feature on banking in Oman  
16.00 AUSTRALIA  
VNG Time Station, full ID’s, Only 5 kw!  
17.49 MADAGASCAR IBC Tamil relay, ID, mostly nx and tlks, exc  
17.67 NEW ZEALAND nx on N Ireland, ID, "Goon Show"  
17.67 NEW ZEALAND classical mx, "In Touch with NZ" featuring oldies  
17.67 NEW ZEALAND nx, Olympic update, ID's  
17.68 CHILE  
relig pop & inspirational mx, ID's, promos  
SR2 24  
 
SAMPLE SHORTWAVE LOGGINGS Con’t  
Freq Country  
(MHz)  
Notes/Contributor  
18.96 SWEDEN  
18.96 SWEDEN  
"Sweden Today", special on Nobel prizes  
"Sweden Today", article on burden of military  
spending on developing countries  
18.96 SWEDEN  
18.98 USA  
Cinema Africa Film Fest being held in Stockholm  
relig mx, sermon, ID  
SR2 25  
 
SR2 26  
 
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. If you need help, please read through your manual carefully, all  
information required to properly build and test your kit is contained within the pages!  
1. DEFECTIVE PARTS: It's always easy to blame a part for a problem in your kit, Before you conclude  
that a part may be bad, thoroughly check your work. Today's semiconductors and passive components  
have reached incredibly high reliability levels, and it’s sad to say that our human construction skills  
have not! But on rare occasions a sour component can slip through. All our kit parts carry the Ramsey  
Electronics Warranty that they are free from defects for a full ninety (90) days from the date of  
purchase. Defective parts will be replaced promptly at our expense. If you suspect any part to be  
defective, please mail it to our factory for testing and replacement. Please send only the defective part  
(s), not the entire kit. The part(s) MUST be returned to us in suitable condition for testing. Please be  
aware that testing can usually determine if the part was truly defective or damaged by assembly or  
usage. Don't be afraid of telling us that you 'blew-it', we're all human and in most cases, replacement  
parts are very reasonably priced.  
2. MISSING PARTS: Before assuming a part value is incorrect, check the parts listing carefully to see  
if it is a critical value such as a specific coil or IC, or whether a RANGE of values is suitable (such as  
"100 to 500 uF"). Often times, common sense will solve a mysterious missing part problem. If you're  
missing five 10K ohm resistors and received five extra 1K resistors, you can pretty much be assured  
that the '1K ohm' resistors are actually the 'missing' 10 K parts ("Hum-m-m, I guess the 'red' band really  
does look orange!") Ramsey Electronics project kits are packed with pride in the USA. If you believe  
we packed an incorrect part or omitted a part clearly indicated in your assembly manual as supplied  
with the basic kit by Ramsey, please write or call us with information on the part you need and proof of  
kit purchase  
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 $18.00, or authorization to charge it to your credit card  
account.  
5. INCLUDE a description of the problem and legible return address. DO NOT send a separate letter;  
include all correspondence with the unit. Please do not include your own hardware such as  
non-Ramsey cabinets, knobs, cables, external battery packs and the like. Ramsey  
Electronics, Inc., reserves the right to refuse repair on ANY item in which we find excessive  
problems or damage due to construction methods. To assist customers in such situations,  
Ramsey Electronics, Inc., reserves the right to solve their needs on a case-by-case basis.  
The repair is $36.00 per hour, regardless of the cost of the kit. Please understand that our technicians  
are not volunteers and that set-up, testing, diagnosis, repair and repacking and paperwork can take  
nearly an hour of paid employee time on even a simple kit. Of course, if we find that a part was  
defective in manufacture, there will be no charge to repair your kit (But please realize that our  
technicians know the difference between a defective part and parts burned out or damaged through  
improper use or assembly).  
4. REFUNDS: You are given ten (10) days to examine our products. If you are not satisfied, you may  
return your unassembled kit with all the parts and instructions and proof of purchase to the factory for a  
full refund. The return package should be packed securely. Insurance is recommended. Please do not  
cause needless delays, read all information carefully.  
SR2 27  
 
SR2 Shortwave Receiver  
Quick Reference Page Guide  
Introduction to the SR2 .......................4  
What You Can Expect to Hear ............4  
Shortwave Listening as a Hobby.........5  
Circuit Description...............................6  
Parts Layout Diagram .........................8  
Parts List.............................................10  
Assembly Instructions .........................12  
Schematic Diagram.............................14  
Shortwave Antenna Ideas...................20  
Initial Testing and Adjustment ............21  
Troubleshooting Tips...........................23  
Ramsey Kit Warranty ..........................27  
REQUIRED TOOLS  
TOTAL SOLDER POINTS  
166  
Soldering Iron Ramsey WLC100  
Thin Rosin Core Solder Ramsey RTS12  
ESTIMATED ASSEMBLY  
TIME  
Beginner .............. 5.0 hrs  
Intermediate......... 3.0 hrs  
Advanced............. 2.0 hrs  
Needle Nose Pliers Ramsey MPP4 or  
RTS05  
Small Diagonal Cutters Ramsey RTS04  
<OR> Technician’s Tool Kit TK405  
ADDITIONAL SUGGESTED ITEMS  
Holder for PC Board/Parts Ramsey HH3  
Desoldering Braid Ramsey RTS08  
Digital Multimeter Ramsey M133  
Manual Price Only: $5.00  
Ramsey Publication No. MSR2  
Assembly and Instruction manual for:  
RAMSEY MODEL NO. SR2  
SHORTWAVE RADIO KIT  
 

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