Ramsey Electronics Car Satellite TV System HR20 User Guide

20 METER (14 MHZ)  
ALL MODE RECEIVER KIT  
Ramsey Electronics Model No.  
HR20  
Here’s the ideal mini-receiver for catching all the busy action on  
20 meters from your office, home or on trips!  
Small in size but BIG in features:  
Easily tunes SSB, CW, RTTY and AM  
Smooth varactor tuning of any desired 250KHz segment of the 20  
meter band, easily retuned  
Front panel RF Gain, Tuning and Volume controls  
Efficient LM-386 Audio amplifier drives speaker or earphones with a  
clean, crisp audio  
Informative manual answers questions on receivers, hookups and  
uses - enhances resale value, too!  
Ideal companion to the Ramsey QRP20 CW Transmitter  
Runs on a standard 9-volt battery  
Clear, concise assembly instructions lead you to a finished product  
that works FIRST time!  
Add our case and knob set for a finished ‘Pro’ look. Cases match all  
Ramsey products.  
 
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..................................14  
Alignment......................................15  
Using your HR20 ..........................16  
Troubleshooting guide ..................19  
Notes for experienced users.........20  
Warranty .......................................26  
HR203  
 
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.  
QRP builders who want a quick, easy and reliable SA602 board kit for 20  
meter projects.  
QRP builders not interested in our warranty or following our step-by-step  
assembly and use directions, but who want to get their hands on our most  
versatile receiver PC-board and parts kit for their own projects.  
The Ramsey HR20 has something fun and easy for each of them.  
Note To Beginners: Building the HR20 is really no harder than any of our other  
receivers in this series. Just follow the directions carefully. All you need to know  
to successfully complete this receiver is contained in this detailed manual.  
Enjoy your HR20 receiver.  
RAMSEY HR-SERIES AMATEUR RECEIVERS:  
All Ramsey Direct Conversion receiver Kits share the same basic PC-boards  
and most components which are not frequency critical. However, there are  
enough differences among the band characteristics, desirable operating  
features for each band, and differences among the people who would most  
typically choose a particular band, that a separate instruction manual is  
published for each receiver.  
Other circuit details which vary from band to band include the tuning range  
provided by the varactor circuit. “Bandspread” for favorite band segments is  
easy on 160 or 80 meters but requires other considerations on higher  
frequencies. Also, some bands appeal to QRP operators more than others, and  
some are better suited for portable and travel use.  
Therefore, we are pleased to assure you that your manual for the HR20  
receiver and the receiver circuit itself have been designed with an  
understanding of typical operating needs and expectations for the 20 meter  
band.  
HR204  
 
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.  
Consequently, our manuals for the 40 and 80 meter receivers are written with  
beginners in mind, since both of these bands offer Novice and Technician  
privileges. The manuals for the 30 and 20 meter versions assume the general  
Ham radio know-how that should accompany a General Class or higher  
license.  
ABOUT DIRECT CONVERSION RECEIVERS:  
The HR20 is a “Direct Conversion” receiving circuit. There is no need for IF  
(intermediate frequency) circuitry. The receiver “processes” the incoming  
signal right at its own frequency, with no need to mix or transform it with  
additional internal oscillators and amplifiers running at intermediate  
frequencies such as 455 KHz.  
The advantage of this type of receiver is that it permits tuning of CW, AM and  
SSB signals with no need for a separate BFO. (A BFO or “beat frequency  
signal oscillator” is an entirely separate oscillator circuit used in the IF  
“intermediate frequency” section of a superhetrodyne receiving circuit). Since  
this frequency is designed specifically for SSB and CW, you will also hear the  
carrier signal of any AM shortwave broadcast station.  
The most elementary “DC” receiver consists of just an oscillator and an  
antenna connected to the inputs of a “Product Detector” whose tiny audio  
output is then amplified for listening. A product detector can be made from  
simple diodes, or a pair of transistors, or a dual gate FET transistor, or various  
IC’s. The Ramsey HR20 efficiently utilizes the Signetics SA602 IC for both the  
tunable oscillator and the product detector circuits, giving the equivalent of  
seven transistors in the mixer-oscillator stages.  
HR205  
 
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. Even  
popular classics like Heath Kit’s HW-8 QRP transceiver exhibit this  
characteristic to a frustrating degree. Another problem with DC receivers is  
called “microphonics” which is a phenomenon where almost anything in the  
physical circuitry of the receiver can act as a sort of microphone or audio  
sound pickup. Touch or bump such radios and you will hear a thump or ring in  
the speaker or earphones. Still another problem is that of AC line hum  
whenever an unregulated power supply is used rather than batteries.  
The Ramsey HR20’s use of the SA602 integrated circuit chip offers a circuit  
configuration that is as immune as any simple superhetrodyne to the classic  
problems with Direct Conversion receivers. The receiver is not as easily  
overloaded by the VOA or Radio Moscow broadcasts, and there are few  
annoying ”microphonics” or incurable AC hum.  
Circuit Description:  
U1 combines a double-balanced active mixer and oscillator in a single 8-pin IC  
chip. L1 peaks the RF input to pins 1 and 2 of U1. L2, with varactor diode D1  
and R2, C1, C2, and C4, control the resonant frequency of U1’s internal  
oscillator. Rotating R2 gives about a 250 KHz tuning range. The audio output  
is fed from pins 4 and 5 through R3 (volume control) directly to the LM 386  
audio amplifier. R1 controls RF gain. C9 boosts the gain figure of the LM 386  
from 20 to 50.  
HR206  
 
PARTS SUPPLIED WITH THE HR20 KIT:  
CAPACITORS:  
1 15pF ceramic disc capacitor [marked 15 or 15K] (C4)  
1 27pF ceramic disc capacitor [marked 27 or 27K] (C13)  
2 36pF ceramic disc capacitor [marked 36 or 36K] (C1,C2)  
4 .01µF disc capacitor [marked 103 or .01 or 10nF] (C3,C5,C6,C7)  
2 4.7 to 10µF electrolytic capacitor (C8,C9)  
3 100-220µF electrolytic capacitor (C10,C11,C12)  
RESISTORS:  
3 10K ohm potentiometers (R1,R2,R3)  
1 270 ohm resistor [red-violet-brown] (R4)  
2 10K resistors [brown-black orange] (R5,R6)  
INDUCTORS:  
2 Shielded Coils [marked 42IF-123] (L1, L2)  
SEMICONDUCTORS:  
1 1N4002 Diode [black epoxy style] (D1)  
1 SA602 IC (U1)  
1 LM386 IC (U2)  
1 6.2 volt Zener Diode [small grey glass body] (D2)  
HARDWARE AND MISC:  
1 Drilled printed-circuit board  
1 9-volt battery hold-down bracket  
1 9-volt battery connector  
1 RCA-style jack [antenna connector] (J1)  
1 subminiature earphone jack (J2)  
1 PC mount pushbutton switch (S1)  
REQUIRED, NOT SUPPLIED:  
9-volt battery (alkaline or heavy duty type)  
Earphone, or small speaker  
Antenna and suitable cable  
OPTIONAL:  
Ramsey Electronics Case and Knob kit, Model CHR or;  
Your own choice of enclosure and hardware  
HR207  
 
"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. Examine the schematic  
diagram and PC-board X-ray illustration as you proceed. In all steps, “install”  
means to insert into the correct PC-board holes, solder properly, and trim all  
excess component leads.  
Use good soldering skills - let your soldering iron heat each connection wire  
so that the wire itself and the foil trace both become hot enough together to  
melt the applied solder so that it flows smoothly around the wire lead and on  
to the PC board trace.  
Mount all electrical parts on the top side of the board provided. This is the  
side that has no traces or pads on it. When parts are installed, they are 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  
securely to the board, and the remaining lead length is then clipped off. The  
clipped off leads should be saved for later use as jumper wires.  
As you can see in examining the circuit board and parts there are many tall  
components such as the potentiometer, capacitors, and switches along with a  
lot of small parts. First you will install the larger components so they can be  
used as markers. So that you don't spend extra time "troubleshooting" we  
strongly recommend that you follow the assembly strategy and step-by-step  
procedures we have provided.  
HR208  
 
HR209  
 
HR20 PARTS LAYOUT DIAGRAM  
HR2010  
 
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. Look at the bottom side and you’ll see a small  
silver and brown tubular part nested within the black plastic base. This is  
actually a ceramic tubular capacitor! It resonates with the tuned circuit for  
for 10.7 MHz. This is the wrong frequency for our purposes so we’ll simply  
remove it and add our own external capacitor (C13). Removing the tubular  
capacitor is not as hard as you might expect, simply crush it completely  
with a small screwdriver or knife. Omitting this step will prevent L1 from  
peaking on 20 meter signals.  
5. Install L1(marked 42IF-123), which tunes or preselects the signal input  
from the antenna through C5 and R1.  
6. Install C13, a 27pF ceramic disc capacitor (marked 27 or 27K).  
7. Install U1, the SA602 IC mixer-oscillator. The marked end of the IC  
(band or dot) must face the FRONT of the PC board. If you wish, install an  
8-pin DIP socket, still remembering to orient and install the SA602  
correctly. Please don't be afraid to solder U1 directly to the board as we  
have seen more repair problems with DIP sockets than from direct  
soldering of IC chips.  
The parts we have put in so far bring the signal from the antenna jack up to  
the RF Gain control (actually the RF attenuator) and to a tuned circuit  
composed of L1 and C13. Inductor L1 allows us to match and tune the 20  
meter band signals to the SA602’s input.  
8. Install C6, .01µF. This capacitor bypasses pin 2 of the SA602 to  
ground. Bypass means to provide a nice low impedance (impedance  
means AC resistance) path to ground.  
9. Install R4, 270 ohms (red-violet-brown), which drops the 9 volt battery  
supply to 6-7 volts, safe for the SA602.  
10. Install D2, 6.2 volt Zener diode. This is the smaller of the two diodes  
and has a painted glass body. This diode acts as a voltage regulator by  
keeping the voltage across it constant.  
11. Install C10, a 100-220µF electrolytic capacitor. Electrolytic capacitors  
HR2011  
 
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. Install C2, 36pF ceramic disc capacitor (marked 36 or 36K). It goes  
across pins 6 and 7 of the SA602 IC. This capacitor is the first step in  
setting up the resonant frequency of the SA602’s internal oscillator, using  
the resonant LC circuit to be created along with C1, C3 and L1.  
14. Install C1, 36pF disc capacitor (marked 36 or 36K).  
15. Install C3, .01µF disc capacitor (marked 103 or .01 or 10nF).  
16. Before installing L2 (marked 42IF-123), its internal capacitor must be  
removed just jike you did for L1. Simply crush it completely with a small  
screwdriver or a knife. Omitting this step will prevent the oscillator from  
tuning the 20 meter band.  
17. Install L2, shielded coil.  
18. Install C4, a 15pF ceramic disc capacitor. C4 adds variable  
capacitance of the varactor tuning network to the oscillator circuit already  
formed by L2, C1, C2 and the SA602.  
19. Install D1, the 1N4002 diode, making sure that the cathode or banded  
end is oriented towards the back of the PC board. This diode performs the  
function of a varactor diode. A varactor diode acts like a variable capacitor  
whose capacitance is controlled by the the voltage across it. There is  
nothing fancy about the varactor diodes, so we are using a common  
rectifier.  
20. Install R5, 10k ohms (brown-black-orange)  
21. Install R2, 10k potentiometer tuning control.  
22. Install R3, 10k potentiometer volume control. This control varies the  
level of audio from pin 4 of the SA602 to the LM386 audio amplifier.  
23. Using a scrap piece of wire, snipped from an installed component,  
install JMP-1.  
OPTION: with JMP-1 installed the bandspread of your tuning dial is the  
normal 250KHz. To get more bandspread in the ham band install C14 as  
shown in the parts diagram and install R7 (2.2k) in place of JMP-1.  
24. Install S1, the power switch.  
HR2012  
 
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. Install C12, 100-220µF electrolytic capacitor; observe polarity. This  
capacitor couples the output of the LM-386 to the speaker jack.  
31. Install C9, 4.7-10µF electrolytic capacitor; observe polarity.  
32. Install speaker jack J2. This jack is a 2.5mm type and mates with any  
2.5mm plug as found on virtually all mini earphones.  
33. Install the 9-volt battery clamp. Use a scrap component lead to loop  
through the two holes in the clamp and through the PC board. Solder the  
leads firmly to the board and to the battery clamp. Do not use too much  
solder on the clamp as this will cause the battery to sit too high and not  
seat securely.  
Congratulations! You have completed the assembly of your HR20 receiver kit.  
Now is a good time to sit back and admire your work and make a final check  
of all solder joints and component placement. It is always better to find errors  
now before you test the HR20.  
HR2013  
 
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.  
REQUIRED FOR INITIAL TESTING AND ALIGNMENT:  
A known frequency standard in the 10MHz range such as:  
Crystal oscillator or,  
RF signal generator or,  
Grid Dip oscillator or,  
QRP transmitter such as a Ramsey QRP-20  
A Ramsey frequency counter, CT-90 or,  
Any accurately calibrated receiver covering 20 meters  
At the least,personal familiarity with the 20 Meter Ham band  
And the following:  
Coil alignment tool ( can be homemade per directions) and  
9-volt battery, antenna earphones or a small speaker.  
Connect the following:  
Fresh, 9-volt battery.  
Earphone or speaker.  
Antenna or at least a random length of wire.  
Adjust the three controls to the middle of their ranges.  
Press the power switch “on”. You should hear background noise  
immediately, at least a gentle hiss.  
See if the volume control works, vary it and notice how the volume  
changes.  
See if the RF gain control has some effect on what you hear.  
If everything seems ok so far, feel the tops of the two IC's with your finger.  
Neither should feel hot or warm  
Slowly rotate the tuning control. At this point you may or may not hear  
anything, since neither coil has been adjusted. If you do hear a few  
whistles as you tune, the SA602 oscillator is working just fine.  
These simple initial checks verify that your receiver is operating well  
enough to proceed to the next section, alignment.  
HR2014  
 
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. If Ham radio and 20 meters are new to you, here’s a  
rough idea of what you can expect to hear on this busy band:  
14.00 - 14.08 MHz - CW, most of it is fairly fast  
14.08 - 14.15 MHz - Teletype (RTTY) and digital operation  
14.10 - 14.20 MHz - SSB voice, many different languages  
14.20 - 14.35 MHz - general SSB voice operation  
NOTE: A miniature transformer alignment tool is used to turn the slugs in L1  
and L2. If you do not have one, make one by gently sanding the tip of a  
wooden match stick, a kabob skewer or other piece of wood or plastic. While it  
seems that a small jeweler’s screwdriver could be used, be aware that its  
metallic construction will make adjustment of L2 very erratic and could  
damage the powdered iron slug. Any kind of metal tip will affect the coil’s true  
value, so that the oscillator will run at one frequency with the metal instrument  
in the coil can, and a completely different frequency by itself.  
For now, set the tuning control to its mid-point. Use the insulated alignment  
tool to gently rotate the slug in the top of L2. If it starts to get tight , DO NOT  
FORCE IT! Instead gently rock it back and forth until it loosens up. You should  
find your 14Mhz reference over a range of approximately 12 to 15 MHz. The  
varactor tuning control can cover any 300 KHz range chosen within the 12 to  
15MHz limits.  
Adjust L1 for maximum received signal strength. Now you’re ready to  
receive on-the-air signals! After you get used to its tuning and  
performance, you can adjust the tuning control, L1 and L2 to get the exact  
tuning range you want.  
ALIGNMENT HINT FOR ALL DIRECT CONVERSION RECEIVERS:  
You will clearly hear the oscillator of your kit - very close to its receiving  
frequency, if you tune around for it on ANY shortwave radio covering the same  
frequency range. Even if your shortwave set does not have a BFO (beat  
frequency oscillator) for CW-SSB, you’ll still hear a powerful ‘hiss or quieting’  
when your shortwave receiver is tuned near the frequency of the HR20. Your  
shortwave receiver is actually picking up the oscillator signal within the HR20!  
HR2015  
 
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.  
Finally, if you intend to use this receiver only for monitoring or working a very  
specific frequency range, you can add a resistor in series with the tuning  
control to achieve the bandspread you want for your own application. For  
details, please see the upcoming section, Notes to Experienced QRP  
Builders.  
We want you to enjoy this economical receiver, whether you use it for portable  
listening or as a base for easy experimentation. Isn’t it amazing the  
performance that can be achieved with just two IC chips?  
TUNING SSB SIGNALS  
As you know, the protocol for the 160 - 80 - 40 Meter Bands is Lower  
Sideband (LSB), with Upper Sideband (USB) used for 20 - 18 - 15 - 12 - 10  
Meter SSB. To check or ‘scan’ a given band for SSB signals, tune your HR20  
up from the low end for USB signals and down from the high end for LSB.  
CW OPERATION  
A direct-conversion receiver lets you hear equal ‘sidebands’ on either side of  
the zero-beat ‘null’ of the exact frequency of the signal to which you are  
listening. Therefore, when adjusting the frequency of your companion Ramsey  
QRP transmitter, be certain that you have in fact tuned to the other station’s  
lower sideband. The two stations will actually be several KHz apart. Because  
this receiver’s oscillator is not shared with a transmitter, as in transceivers,  
there is no need for separate RIT (receiver incremental tuning).  
ON THE AIR TRANS-RECEIVING  
Let’s assume that you plan to use this receiver together with a Ramsey QRP  
transmitter, which provides an RF protected receiver antenna jack. While the  
receiver will be protected from RF damage from the transmitter, do not expect  
to monitor your own signal on this receiver while transmitting unless you are a  
QRP design expert and do not care about future factory service from Ramsey.  
Even with the circuit protection, the RF signal is just too much for the SA602.  
The transmitter signal overpowers the SA602, disrupting the internal oscillator.  
However, the receiver can handle the output of a crystal oscillator or VFO for  
frequency spotting purposes.  
A better operating arrangement will consist of a T-R switch, either a manual  
switch or break-in delay relay circuit. This switching circuit can disconnect the  
HR2016  
 
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. Speaker quality and well-  
designed enclosures have their clear purposes! A reasonable speaker in a  
box delivers a pleasant listening volume. On the other hand, the LM386  
indeed can deliver more audio output punch than is developed in our HR-  
series kits. For example, our FM receivers, using the same LM386 audio IC,  
deliver more volume. These receivers, however, take advantage of IF  
amplifiers, drift-compensation and crystal controlled oscillators built into mass  
production sophisticated FM receiver ICs. A heavier drain on the HR20’s  
battery by stronger audio will quickly result in chirpy signals and oscillator drift  
as well as the need for frequent battery replacement. Remember the SA602  
circuits similar to the Ramsey HR-series generally call for sets of C or D cell  
batteries! For Experienced Builders more information regarding audio output  
is in the general notes.  
The simple design of the audio stage of the Ramsey HR20 receiver assumes  
preference for headphone or small speaker operation, low battery drain and  
general economy.  
HR2017  
 
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.  
ADDING AN LED POWER ON INDICATOR  
For many people, a pilot lamp to indicate “power on” is more than a nice  
touch. They expect it and depend on it , reminding us that “real radios glow in  
the dark!”  
Adding a simple LED power-on indicator to your Ramsey HR20 is easy. All  
you need is the LED itself and a small 1K or 2.2K resistor. Study the PC  
traces between the positive battery supply wire and the on-off switch. The  
unused connectors on top of your switch are an ideal point to get the + DC  
voltage needed for the anode (longer lead) of the LED. Plan where and how  
you wish to install the LED in your enclosure. Locating the LED immediately  
above the on-off switch is ideal. The simplest way to make a neat installation  
is to drill a hole just sightly smaller than the diameter of the LED. Then,  
enlarge the hole a little bit at a time, just enough to let the LED be pressed in  
and held firmly. The resistor may be connected to either the anode or cathode  
side of the LED, but the anode must be connect to the + DC with the cathode  
connected to the nearest common ground.  
If you are wondering why we did not include these pennies worth of parts with  
your kit , you can believe any of the following reasons: 1)We wanted to stretch  
your battery budget and the current draw on the LED is about 6ma. How long  
will your battery last if you leave your receiver on for a few days, just like we  
leave on our computers and Ham gear on all the time? (2) We thought you’d  
have more fun planning and installing your own lamp that glows in the dark!  
HR2018  
 
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.  
SOLUTION: Try a different set of headphones, different speaker or external  
audio amplifier. Some cheap headphones designed for casual  
music listening have an undesirable filtering effect on CW  
signals.  
PROBLEM: Oscillator inoperative or wrong frequency.  
SOLUTION: In addition to checking solder joints, be sure that L1 is  
oriented correctly and that C1, C2, C3 and C4 are installed in  
correct positions.  
PROBLEM: Loud AC hum or buzz.  
SOLUTION: If you are using the receiver with a battery or simply for listening  
(i.e.: not connected to a transmitter or a AC power adapter),  
these are likely causes of the AC hum:  
No ground connection.  
Receiver located too close to an AC device such an older electric  
clock, AC-powered radio, etc.  
Antenna very close to a power cord or house wiring. If your  
receiver is being used with a transmitter, the transmitter power  
supply may be the source of the unwanted AC hum. If you are  
using a 9-volt AC power adapter, the adapter design may not be  
of sufficient quality for this application. Try a bypass capacitor, or  
a different adapter or a well-designed and filtered DC power  
supply.  
A careful check of all construction WILL solve your problem. Over 95% of the  
kits returned for repair have nothing more than a simple assembly or  
construction error!  
HR2019  
 
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. If you know what you are doing with  
DC receiver design, we encourage you to use our HR-series for reliable  
building blocks for achieving maximum performance for your own application.  
If a good idea does not work as expected, you can easily restore your Ramsey  
receiver to its original circuit configuration.  
Our job has been to keep in stock for immediate delivery a good basic design,  
a quality PC board with plenty of work room, useful front panel controls,  
correct and adjustable inductors, workable varactor tuning and the popular  
SA602. We know these receivers WORK, as specified, and that the ONLY  
reason any HR-receiver will not work after the 1-2 hours needed for assembly  
is if we packed the wrong parts or you put them in wrong. Once you are sure  
the receiver performs as specified, there is a lot you can do to coax maximum  
performance from the basic circuit.  
For instance, if you choose a DC power source other than the 9-volt battery,  
the space allowed for the battery offers plenty of room for a top mounted  
perfboard or PC-board for preamp stages and or any sort of passive or active  
audio filter that suits your needs. Keep your work neat with short leads so as  
not to introduce broadcast station overload.  
ALTERNATE POWER SOURCES:  
Most of the HR20 circuitry can be operated from 6 to 14 volts without damage  
or significant modification. However, it is quite important that you carefully  
hook up with the correct polarity; reverse polarity or excessive voltages WILL  
damage your kit.  
HR2020  
 
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. If your interest is in monitoring SSB, the normal alignment will  
work fine. For optimum CW only listening, set the lower band edge with the  
tuning control in the 12:00 position of its range.  
In planning any ‘bandspread’ improvement, it is useful to understand exactly  
how varactor tuning works. The control level varies the amount of DC voltage  
applied to the diode. The highest produces the lowest capacitance, while the  
lowest voltage yields the highest capacitance. The spread is typically about 20  
to 30pF from minimum to maximum.The goal in achieving bandspread or  
‘fine - tuning’ is to achieve a smaller variation in capacitance with the  
comfortable tuning of a knob.  
Any resistor in a range from 500 ohms to 3000 ohms, connected in series with  
the ground lead of R2, will set a limiting effect on varactor capacitance range  
and therefore create a “bandspread “ effect. The higher the resistance value,  
the shorter the available tuning range.  
If you wish to reduce the tuning range of R2 down to 20 or 30KHz or even less  
for a favorite band segment or calling frequency, reducing the value of C4 will  
decrease the capacitance effect of the varactor diode, D1. Values from 2 to 5  
pf may give you exactly the tuning range you are looking for.  
If you are using your own enclosure and have room for a separate fine tuning  
control, one useful choice is a 250 ohm speaker attenuation rheostat (Radio  
Shack model no. 271-265) wired in series with either outside ‘leg’ of the main  
tuning control. Such a control can make fine adjustments to a CW signal so  
the tone is pleasant and smooth sounding.  
If you want the opposite of bandspread (that is as MUCH frequency range as  
possible over full rotation of the tuning knob ) increase the value of C4. This  
will cause the varactor diode to have greater effect on the tuning. Try values of  
33pF up to 100pF.  
HR2021  
 
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. Even though  
this tunable oscillator design takes good advantage of the SA602’s capabilities  
and offers nice tuning range from a simple varactor circuit, we do not  
represent it as suitable for transmitter frequency control or for demanding  
receiver applications. In any ham VFO design, ANY unshielded or  
uncompensated oscillator components are susceptible to the influences of  
temperature change and of nearby moving objects. The use of a suitable  
enclosure and secure mounting of the PC board within that enclosure will  
maximize the stability of the oscillator. One to two KHz of slow drift may be  
expected as components warm to operating temperature; after that the  
oscillator is reasonably stable.  
OTHER METHODS OF DIAL CALIBRATION:  
A easy way of making your own dial is to paste a small rectangle of paper  
behind the tuning dial knob. Then as you tune in different frequencies, pencil  
in on the paper the received frequency. Or a simple logging scale may be  
affixed behind the tuning knob on the front panel. A logging scale is simply a  
set of numbers for adjusting a control. For example, 4 might represent 7.1MHz  
and 5.5 being 7.12MHz, and so forth.  
DIRECT FREQUENCY READOUT:  
A novel advantage of the simple direct conversion receiver is that a general  
purpose frequency counter may be used to give a direct readout of the  
oscillator frequency. While you could experiment with an RF pickup loop or  
tuned circuit and counter preamplifier to boost the oscillator’s tiny output to a  
level suitable for the counter, the most reliable method is to wire a high-  
impedance counter probe line directly to pin 7 of the SA602, terminated to a  
rear panel frequency counter connection of your choice. This will consist of a  
short piece of mini-coax to a 1 megohm resistor bridged by a 27 to 33pf  
capacitor as shown below:  
With the RF gain turned all the way up , it may be possible to hear the  
counter’s busy humming action in the background, but not to a serious  
degree. It drops out with a slight reduction of the RF gain. If you decided to  
add such a counter connection to your receiver, remember that the coax as  
well as the coupling capacitor become part of the oscillator circuit. Make the  
coaxial cable connecting the counter to the receiver as short as possible. You  
will experience a frequency change of several KHz when connecting or  
disconnecting the counter. Also, this additional capacitance in the oscillator  
circuit reduces the tuning range to approximately 100 KHz, thus offering  
HR2022  
 
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. There is certainly space on the HR-30 circuit board to  
install an audio preamplifier (i.e. 2N3904, or minimum-gain LM386) in the  
circuit trace between C8, the audio-coupling capacitor from pin 4 of the SA602  
to the volume control.  
The following is an audio preamplifier idea submitted by one of our customers.  
Ramsey Electronics in no way warrants that this modification will achieve any  
particular ideal signal-to-noise ratio or audio frequency response, but is does  
significantly boost the output of the SA602 reaching the LM386 audio amplifier  
IC. Instead of the traditional transistor audio preamp circuit, an additional  
LM386 is used in its minimum gain configuration (gain of 40), plus one  
electrolytic capacitor (1 to 10µF) to achieve minimum parts and PC-board  
drilling. This use of two LM386 ICs amplifies the audio signal of the SA602 by  
a factor of 1000.  
This modification requires cutting the circuit trace leading from C8 to the  
volume control, R3  
27  
pF  
TO  
NE60  
2
PIN  
7
COUNT  
ER  
1
MEGOH  
Additional LM386 used as AF preamplifier between U1 and U2:  
Pins 1,7,8: not used  
Pins 2,4: to ground  
Pin 3 to ‘-’ side of c*(2.2pF)  
pin 5 to ‘+’ side of new 1 to 10µF capacitor  
Pin 6 to ‘+’ DC supply board trace  
HR2023  
 
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. If the gain  
is too much, use a resistor to reduce the voltage supplied to pin 6 of preamp  
LM386  
Finally, we remind you again that modification of any PC board puts you on  
your own, voiding your factory warranty, making your unit ineligible for factory  
repair. Make sure the receiver is working properly and that you understand  
how to use and repair it BEFORE making any changes in the original design.  
Enjoy it!  
HR2024  
 
CONSTRUCTION NOTES:  
HR2025  
 
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  
500µF"). 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.  
HR2026  
 
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. 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 $50.00 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.  
HR2027  
 
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....................................... 26  
REQUIRED TOOLS  
Soldering Iron Ramsey WLC100  
Thin Rosin Core Solder Ramsey RTS12  
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  
TOTAL SOLDER POINTS  
84  
ESTIMATED ASSEMBLY  
TIME  
Beginner...............3.0 hrs  
Intermediate .........2.0 hrs  
Advanced .............1.0 hr  
Price: $5.00  
Ramsey Publication No. MHR20  
Assembly and Instruction manual for:  
RAMSEY MODEL NO. HR20  
AMATEUR RECEIVER KIT  
 

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