Ramsey FR10 User Manual

10 METER FM

RECEIVER KIT

Ramsey Electronics Model No. FR10

Check out the 10 meter action with this simple and fun
to build FM receiver. Receive crystal-clear signals from
thousands of miles away! Ten meters is a fascinating
band! Tune the entire 10 Meter band or the VHF low
Police and Fire band.

• Tunes any 5 MHz portion of the 25 to 35 MHz band.

• Excellent performance, less than 1 uV sensitivity.

• Tuned input, low noise preamp stage.

• True Dual-conversion superhet design with 2 pole

Ceramic High IF and 6 pole Ceramic low IF filters!

• Front Panel Volume, Squelch, and Tuning controls.

• Excellent receiver for beginners and seasoned pros!

• Informative manual answers questions on theory, hook-

ups, and uses - enhances resale value, too!

• Add our case set for a finished ‘Pro’ look. Cases match

all Ramsey products.

• Clear, concise assembly instruction carefully guides

you to a finished kit that works the FIRST time!

FR-10 • 1

PARTIAL LIST OF AVAILABLE KITS
RAMSEY TRANSMITTER KITS

· FM10A FM Stereo Transmitter

· FM25B Synthesized FM Stereo Transmitter

· AM25 Synthesized AM Transmitter

· AM1 AM Transmitter

RAMSEY RECEIVER KITS

· FR1 FM Broadcast Receiver

· AR1 Aircraft Band Receiver

· AA7 Active Antenna

· SC1 Shortwave Converter

RAMSEY HOBBY KITS

· SG7 Personal Speed Radar

· SS70 Speech Scrambler

· TT1 Telephone Recorder

· SP1 Speakerphone

· MD3 Microwave Motion Detector

· TFM3 Tri-Field Meter

· LC1 Inductance-Capacitance Meter

· ECG1 Heart Monitor

RAMSEY AMATEUR RADIO KITS

· HR Series HF All Mode Receivers

· QRP Series HF CW Transmitters

· CPO3 Code Practice Oscillator

· DDF1 Doppler Direction Finder

· 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.

FR10 10 METER FM RECEIVER KIT INSTRUCTION MANUAL

Ramsey Electronics publication NO. MFR10 Rev. E1

First printing: January 1992

COPYRIGHT 1992 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.

FR-10 • 2

Ramsey Publication No. MFR10

Price $5.00

KIT ASSEMBLY

AND INSTRUCTION MANUAL FOR

FR10 10 METER

FM RECEIVER KIT

TABLE OF CONTENTS

I

ntroduction to the FR10 ................ 4

Circuit Description ......................... 5

Parts List ........................................ 6

Simplified Block Diagram .............. 8

Parts Layout Diagram .................... 9

FR10 Assembly Instructions .......... 11

Schematic Diagram ....................... 14

Testing and Alignment ................... 20

Enclosure Ideas ............................. 23

Troubleshooting Guide .................. 24

Notes for Advanced Users ............ 25

Ramsey Kit Warranty ..................... 27

FR-10 • 3

RAMSEY ELECTRONICS, INC.

590 Fishers Station Drive

Victor, New York 14564

Phone [phone]

Fax [phone]

www.ramseykits.com

INTRODUCTION

There's not a lot to say about using the FR10 receiver once its been
correctly built and aligned. If 10 meters is "dead" you'll hear little or
nothing. If Ten is "open" there will be an amazing variety of crystal­clear signals from many thousands of miles away.

In the first serious test of this receiver, booming signals from the US
Northeast and Midwest as well as Scotland and Ireland were logged
from a site in Florida! The strength and clarity of GM4DLU in Scotland
was simply astounding! Another listening session logged a station in
Washington, DC conversing with one in Wisconsin via a repeater in
Dallas!

This receiver is a good project for amateurs wishing to become more
familiar with 10 meter FM before choosing a transceiver, or for those
active on 10 who want an inexpensive receiver to take on trips, keep
in a briefcase or to watch for band openings.

Most Ramsey Electronics can be classified as "Skill Level 1" if we use
the old Heathkit guidelines for ease of assembly. That means that our
kits are intended to be successful for first-time kit builders. This FR10
FM Receiver is best regarded as a "Skill Level 2" project, and should
not be taken lightly, even by experienced, licensed radio amateurs.

Still, this step-by-step manual is written with the beginner in mind,
because we are well aware of the fascination that Ten Meters and its
maze of repeaters holds for newcomers, which means this could be
your very first kit project. The same holds true for those who just want
to peek in on LOW VHF public service communications without the
cost of a scanner. To be honest, we'd like to see first-time builders
start out with an easier kit such as the Ramsey HR40 Forty Meter
receiver before assembling the FR10, but we are confident that you
can construct the FR10 successfully if you follow this manual carefully
and patiently.

Before beginning the project or even studying the circuit description, it
is worthwhile to develop some prior respect for how much receiver is
packed onto the circuit board. The nine semiconductor devices
(diodes, transistors and IC chips) give the equivalent of about 30 or
more transistors and diodes. And, in addition to four inductors, a

FR-10 • 4

crystal and two ceramic filters, there are nearly 60 capacitors and
resistors. Surely, all that should result in a decent receiver! You could
easily spend twice the money plus hours of time trying to gather the
equivalent parts from catalogs and still need to make your own circuit
board.

BUILDING YOUR FR10 KIT

There are just over 200 solder connections on the FR10 printed circuit
board. That means your work could be 99% excellent and you could
STILL have 2 or 3 cold solder points or solder bridges. Since this circuit
is more sophisticated than a direct-conversion HF receiver or a simple
transmitter, a beginner or casual amateur could have a harder time
tracing a problem due to a poor solder connection. Therefore, PLEASE
take us seriously when we say that good soldering is essential to the
proper operation of your receiver!

 Use a 25-watt soldering pencil with a clean, sharp tip.
 Use only rosin-core solder intended for electronics use.
 Use bright lighting. A magnifying lamp or bench-style magnifier may

be helpful.

 Do your work in stages, taking breaks to check your work.
 Carefully brush away wire cuttings so they don't lodge between

solder connections.

FR10 CIRCUIT DESCRIPTION

VHF signals from the antenna are amplified through the tuned input
circuit (L1,C3 and L2,C4) by Q1, a microwave bipolar transistor. Q1's
output is fed to the input of the SA602 IC, an efficient single-package (8­pin DIP) mixer-product detector-oscillator. The tunable oscillator section
of the SA602 is aligned to operate at 10.7 MHz higher than the signal fed
and amplified by Q1. For example, to receive 222-227 MHz signals, the
oscillator must tune 232.7 to 237.7 MHz in order for the SA602's mixing
capability to produce a steady 10.7 MHz output signal to the rest of the
circuit. The oscillator frequency is determined by L3 and its associated
capacitors, and varied by the varactor tuning network using D1 and
varied by R1.

The output from pin 4 of the SA602 passes through a ceramic 10.7 MHz
filter, amplified by transistor Q2 and applied to input pin 18 of U2. Q3
provides AFC (automatic frequency control) by keeping the local

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oscillator of U1 from drifting away from an incoming signal. This is
accomplished by tuning the varactor circuit in the direction opposite the
drift.

The MC3359 IC has an internal oscillator controlled by the 10.24 MHz
crystal. The 10.24 MHz signal is mixed with the 10.7 MHz input from U1
to convert down to the low IF of 450 KHz. The 450 KHz IF is filtered by
FL2 and then amplified by a limiting amplifier in U2. Audio demodulation
takes place in the quadrature detector, with L4 adjusting the detector.

The audio modulation is detected in U2, and the background noise is
used to control the squelch. U3 amplifies the audio output from pin 10 of
U2 to a practical level for speaker or headphone operation. Pin 16 of U2
will ground the input of U3 when the squelch is closed.

L4, a 450 KHz IF coil, permits adjustment of the 90-degree voltage­current phasing ("quadrature") of FL2's output to the FM detector
demodulator (pin 8 of the MC3359).

PARTS LIST

Inductors

 2 .33 uH inductors [looks like a resistor with 2 orange and 2 silver

bands] (L1,L2)

 1 slug-tuned coil [blue color] (L3)
 1 shielded transformer coil [marked LB 53303] (L4)

Semiconductors and IC's

 1 2SC2498 or 2SC2570A transistor (Q1)
 3 2N3904 transistor (Q2,Q3,Q4)
 1 SA602 8-pin IC (U1)
 1 MC3359 18-pin FM receiver IC (U2)
 1 LM386 8-pin audio amplifier IC (U3)
 1 Varactor diode, MV2209 [looks like a transistor with two leads]

(D1)

 1 1N4148 signal diode (D2)

Special Components

 1 10.24 MHz Crystal (Y1)
 1 10.7 MHz ceramic filter [brown, molded, 3 leads] (FL1)
 1 450 KHz ceramic filter [black, square] (FL2)

FR-10 • 6

Fixed Resistors

 1 2 ohm [red-black-gold] (R22)
 3 270 ohm [red-violet-brown] (R6,9,20)
 1 470 ohm [yellow-violet-brown] (R5)
 2 1K ohm [brown-black-red] (R11,12)
 3 10K ohm [brown-black-orange] (R7,17,19)
 1 18K ohm [brown-gray-orange] (R18)
 1 33K ohm [orange-orange-orange] (R14)
 4 47K ohm [yellow-violet-orange] (R4,8,13,21)
 1 100K ohm [brown-black-yellow] (R16)
 1 470K ohm [yellow-violet-yellow] (R15)
 1 1 megohm [brown-black-green] (R10)

Capacitors



1 10 pF (C5)

 2 22 pF (C2,19)
 1 47 pF (C12)
 2 56 pF (C3,4)
 5 100 pF [marked 100, 101, or 101K] (C1,6,9,10,22)
 1 220 pF [marked 220 or 221] (C18)
 6 .001 uF [marked .001 or 102 or 1 nF] (C7,8,20,23,24,25)
 9 .01 uF [marked .01 or 103 or 10 nF]

(C11,13,16,17,21,26,28,29,31)

 1 .1 uF [marked .1 or 104] (C34)
 1 1.0 uF electrolytic (C27)
 3 4.7 or 10 uF electrolytic (C15,30,36)
 4 100 to 220 uF electrolytic (C14,32,33,35)

Controls and Hardware

 1 Printed circuit board
 3 10K ohm potentiometer (R1,R2,R3)
 1 DPDT push switch (S1)
 1 PC mount RCA jack (J1)
 1 PC mount subminiature speaker jack (J2)
 1 9-volt battery bracket
 1 9-volt battery snap-on clip

REQUIRED, NOT SUPPLIED

 1 9-volt alkaline battery
 1 VHF antenna with cable terminated in RCA-style plug or adapter
 1 Speaker or headphones

FR-10 • 7

FR-10 BLOCK DIAGRAM

U2, 3359

U1

SA602

MIXER

FR-10 • 8

FR-10 PARTS LAYOUT DIAGRAM

FR-10 • 9