Ramsey HR20 User Manual

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.

HR20• 1

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 Transmitter Companion

RAMSEY AMATEUR RADIO KITS

• HR Series HF All Mode Receivers

• QRP Series HF CW Transmitters

• DDF1 Doppler Direction Finder

• CPO3 Code Practice Oscillator

• QRP Power Amplifiers

RAMSEY MINI-KITS
Many other kits are available for hobby, school, scouts and just plain FUN. New
kits are always under development. Write or call for our free Ramsey catalog.

HR20 AMATEUR RECEIVER KIT INSTRUCTION MANUAL

Ramsey Electronics publication No. MHR20 Revision C1

First printing: January 1995

COPYRIGHT 1994 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York

14564. All rights reserved. No portion of this publication may be copied or duplicated without the
written permission of Ramsey Electronics, Inc. Printed in the United States of America.

HR20• 2

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

HR20• 3

RAMSEY ELECTRONICS, INC.

590 Fishers Station Drive

Victor, New York 14564

Phone [phone]

Fax [phone]

www.ramseykits.com

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.

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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.

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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.

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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

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"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.

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