Ramsey Electronics FR-10 User guide

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 •2
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 •3
FR10 10 METER
FM RECEIVER KIT
Ramsey Publication No. MFR10
Price $5.00
TABLE OF CONTENTS
Introduction 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
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR

FR-10 •4
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 crystal-
clear 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 •5
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 (8-
pin 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

FR-10 •6
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 voltage-
current 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 •7
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 •8
U2, 3359
FR-10 BLOCK DIAGRAM
U1
SA602
MIXER

FR-10 •9
FR-10 PARTS LAYOUT DIAGRAM

FR-10 •10
NOTE CONCERNING THE AUDIO OUTPUT JACK
Your receiver kit is supplied with a standard subminiature 2.5 mm
(3/32”) audio jack, which mates with commonly available earphone
plugs and adapters available at Radio Shack, such as 274-290 (plug) or
274-327 (adapter for 1/8” mono plug). If you prefer to use another size
and style jack, we suggest that you still install the original jack and then
wire your own jack in parallel with it rather than rough up the PC board
to accommodate your jack.
SEMICONDUCTOR REPLACEMENT DATA
U1 SA602 Contact Ramsey Factory
U2 MC3359 (Motorola) ECG860 or SK7731
U3 LM386 (National) available at Radio Shack, other suppliers
Q1 2SC2498 or 2570 ECG10 or SK9139
Q2,3 2N3904 available at Radio Shack, other suppliers
D1 BB405 contact Ramsey Factory
D2 1N4148 available at Radio Shack, other suppliers

FR-10 •11
RAMSEY “Learn-As-You-Build” KIT ASSEMBLY:
We have a twofold "strategy" for the order of the following kit assembly
steps. First, we install parts in physical relationship to each other, so
there's minimal chance of inserting wires into wrong holes. Second,
whenever possible, we install in an order that fits our "Learn-As-You
Build" Kit building philosophy.
FOR EACH PART, OUR WORD "INSTALL" ALWAYS MEANS THESE
STEPS:
1. Pick the CORRECT part value to start with.
2. Insert it into the CORRECT PC board location.
3. ORIENT it correctly, which means: PLEASE follow the PC board
drawing and the written directions for ALL parts where there's a
right way AND a wrong way to solder it in. (Diode bands,
electrolytic capacitor polarity, transistor shapes, dotted or
notched ends of IC's, and so forth.)
4. Solder ALL connections unless directed otherwise. Use enough heat
and solder flow for clean, shiny, completed connections. Don't
be afraid of ANY pen-style soldering iron having enough heat to
damage a component.
5. Trim or "nip" excess wire lengths after soldering.
NOTE: Save some of the longer wire scraps nipped from resistors and
capacitors. These will be used to form wire jumpers (JMP1, etc.) to be
soldered in just like parts during these construction steps.
Now, let's start building!
1. Press S1 firmly into its six holes and solder all six pins. The
switch fits the board only one way. Ignore the other set of six
solder connectors on the switch.
2. Install J1, the RCA-style antenna jack. Solder all 4 points.
3. Install J2, the subminiature phone jack. Solder all three points.
Be gentle and patient in inserting, so as not to damage the
solder tabs.
4. Install controls R1, R2 and R3. Insert the three PC mounted
controls into their positions. Check that the controls are pressed
in firmly and straight against the top of the board. Solder the

FR-10 •12
three center pins and then the two larger mechanical mounting tabs.
Use enough solder for a solid connection.
Also, if you plan to use an enclosure other than the custom Ramsey
enclosure and knob kit, you may wish to locate the controls differently
than provided by the PC board. In this case, the control lugs are wired to
the PC board using your own insulated hookup wire, kept as short as
possible for neat installation.
FURTHER COMPONENT INSTALLATION
All "directions" on the PC board (i.e.: right, left, above, below and so
forth) assume orientation of your board as shown in the parts layout
diagram. Therefore the rear of the board (connectors) is the lower end,
and the front (controls) is the upper end.
1. ANTENNA INPUT AND TUNED RF PREAMPLIFIER
❒5. Install C1, 100 pf disc capacitor [marked 100 or 101].
❒6. Install C2, 22 pf.
❒7. Install C3, 56 pf.
❒8. Install L1, .33 uH inductor. L1 resembles a resistor body with
two orange stripes painted on it.
❒9. Install C4, 56 pf.
❒10. Install L2, the other .33 uH coil just like L1 above.
❒11. Install C5, 10 pf.
❒12. Clearly identify Q1, the 2SC2498 or 2SC2570A transistor. Do not
confuse it with the other transistors supplied. Position Q1 as shown
on the PC board layout, with the flat side facing to the right, toward
the middle of the board. Press the transistor snugly into the PC
board so that only a minimum amount of wire lead is exposed above
the board. When soldering, don't be afraid to use enough heat to
make good clean connections.
❒13. Install R4, 47K, just to the left of Q1. [yellow-violet-orange].
❒14. Install C6, 100 pf [marked 100 or 101].
❒15. Install R5, 470 ohms [yellow-violet-brown].

FR-10 •13
2. SA602 OSCILLATOR-MIXER and VARACTOR TUNING
16. Install R6, 270 ohms. [red-violet-brown]
17. Install C7, a .001 uF bypass capacitor [marked .001,102, or
1 nF].
In installing the SA602 IC, you may wish to use an 8-pin DIP socket
rather than soldering the IC directly to the board. Reasons for doing this
might include the peace of mind of beginners afraid of damaging the IC,
or experienced builders testing the merits of the SA602's cousin, the
SE602. However, please be aware that we have seen more service
problems with improper socket insertion than from soldering heat
damage to IC's. Even if this is your first IC, don't be afraid to use enough
heat to make 8 clean connections, but DO be sure to correctly orient the
end marked by a band, dot, or notch. Before soldering, make sure that
the IC or socket is perfectly flat against the top of the PC board.
❒18. Install U1, the SA602 in accord with the preceding directions.
❒19. Install the FL1 ceramic filter. This component is a brown, molded
"blob" with 3 leads and may be installed either way.
❒20. Install jumper wire JMP4. Use a scrap component lead wire bent
into a small loop that connects the two PC board holes. Jumpers
act as "bridges" over PC board traces underneath.
❒21. Install C8, .001 uf [marked .001 or 102].
❒22. Install C10, 100 pf [marked 100 or 101].
❒23. Install R7, 10K [brown-black-orange].
❒24. Install C9, 100 pf [marked 100 or 101].
❒25. Install C11, .01 uf [marked .01 or 103 or 10 nf].
❒26. Install L3. It is important that the body of this coil be snug
against the PC board for mechanical stability, which directly
affects the frequency stability of the receiver. Make good, solid
solder connections!
❒27. Install C12, 47 pf.

FR-10 •14

FR-10 •15

FR-10 •16
❒28. Install varactor diode D1.It looks like a transistor with just two
leads. The flat side faces L3 so be sure to orient it correctly.
❒29. Install R8, 47K ohms [yellow-violet-orange].
❒30. Install R9, 270 ohms [red-violet-brown].
❒31. Install C13, .01 uf [marked .01 or 103 or 10nf].
❒32. Installation of C14. This is the first of the electrolytic or
"polarized" capacitors that you will install. This means these
capacitors have a positive (+) and negative (-) side and therefore
a right way and wrong way of installation. Ordinarily, only the
negative side is marked on the capacitor body, a dark band with
the (-) sign clearly shown. The value of C14 is not critical and
may be any value from 100 to 220 uf.
❒33. Install C14, 100 to 220 uf, observing correct polarity.
❒34. Install C15, 4.7 or 10 uf, observing correct polarity.
❒35. Install jumper JMP1.
❒36. Install jumper JMP3.
PROGRESS SUMMARY
So far, you have wired the tuned input from the antenna, the RF
preamplifier, and the SA602 mixer-oscillator, including the varactor
tuning circuit. The work you have done so far has actually formed a
simple receiver capable of tuning in VHF signals of all kinds and
converting them to a low-level 10.7 MHz output to be amplified by Q2.
This is a good time to review the steps completed so far before
proceeding. Due to the many functions of the MC3359 FM receiver IC,
further assembly steps will be in the order of easiest parts installation.

FR-10 •17
3. TRANSISTOR COUPLING & AFC CIRCUITS, VOLUME &
SQUELCH CONTROLS
❒37. Install Q2, a 2N3904 transistor. Observe correct positioning of
the flat side.
❒38. Install R13, 47K ohms [yellow-violet-orange].
❒39. Install C20, .001 uf [marked .001 or 102].
❒40. Install R12, 1K ohms [brown-black-red].
❒41. Install Q3, 2N3904 transistor.
❒42. Install R10, 1 megohm [brown-black-green].
❒43. Install R11, 1K ohms [brown-black-red].
❒44. Install R22, 2 ohms [red-black-gold].
❒45. Install C29, .01 uf [marked .01 or 103 or 10nf].
❒46. Install C30, 4.7 or 10 uf electrolytic, observe correct polarity.
❒47. Install R18, 18K ohms. [brown-gray-orange]
❒48. Install C28, .01 uf [marked .01 or 103 or 10nf].
❒49. Install R19, 10K ohms [brown-black-orange].
❒50. Install jumper wire, JMP2.
❒51. Install C34, .1 uf [marked .1 or 104].
❒52. Install R21, 47K ohms [yellow-violet-orange].
❒53. Install C35, 100 to 220 uf electrolytic, observe polarity.
❒54. Install R20, 270 ohms [red-violet-brown].
❒55. Install Q4, 2N3904 transistor.
4. MC3359 FM IC and ASSOCIATED COMPONENTS
❒56. Install R17, 10K ohms [brown-black-orange].
❒57. Install R14, 33K ohms [orange-orange-orange].

FR-10 •18
❒58. Install C24, .001 uf [marked .001 or 102].
❒59. Install C25, .001 uf [marked .001 or 102].
❒60. Install C26, .01 uf [marked .01 or 103 or 10nf].
❒61. Install L4, the 450 KHz quadrature coil, soldering the two pins
and the two mounting tabs.
❒62. Install U2, the MC3359 IC. As in the case of the SA602 IC, you
could choose to install an 18-pin IC socket rather than soldering the
IC directly. Re-read the previous discussion of IC sockets offered for
the installation of U1. Larger IC's such as the MC3359 require
considerably more care in socket insertion.Notice that the end of the
IC marked by a band or dot and must be oriented correctly as shown
on the PC parts layout diagram. Solder each of the 18 connections
carefully. Make sure you have good lighting as well as good
technique to make sure that no solder "bridges" flow between the
connections.
❒63. Install C22, 100 pf [marked 100 or 101].
❒64. Install C16, .01 uf [marked .01 or 103 or 10nf].
❒65. Install C17, .01 uf [marked .01 or 103 or 10nf].
❒66. Install C21, .01 uf [marked .01 or 103 or 10nf].
❒67. Install C18, 220 pf [marked 220 or 221].
❒68. Install C19, 22 pf.
❒69. Install Y1, the 10.24 MHz. crystal. No special procedure is
required. Simply press the crystal firmly into its holes as far as it
will go, and make good solder connections.
❒70. Install FL2, the 450 KHz filter. Its three leads are delicate, and
fit in only one way.
❒71. Install C23, .001 uf [marked .001 or 102].
❒72. Install C27, 1 uf electrolytic, observe correct polarity.
❒73. Install D2, the 1N914/1N4148 signal diode, observe correct
orientation of the banded cathode end.
❒74. Install R16, 100K ohms [brown-black-yellow].

FR-10 •19
❒75. Install R15, 470K ohms [yellow-violet-yellow].
5. FINAL CONNECTIONS: THE LM386 AUDIO IC STAGE
You now have a working FM receiver ready for adjustment. The output of
the MC3359 FM IC simply needs to be boosted to listening level. A few
more connections, and your receiver will be ready for adjustment and
testing! Now would be a good time to review some of your previous work
and also to make sure you have on hand what you'll need for testing:
antenna, fresh battery, earphone or speaker with correct plug or adapter.
❒76. Review the instructions for installing U1 and U2. Insert U3, the
LM386 IC with the band or dot oriented correctly. Solder the 8
connections.
❒77. Install C32, a 100 to 220 uf electrolytic, observe correct polarity.
❒78. Install C31, .01 uf [marked .01 or 103 or 10nf].
❒79. Install C36, 4.7 or 10 uf electrolytic, observe polarity.
❒80. Install C33, 100 to 220 uf electrolytic, observe polarity.
❒81. Install the battery snap terminal in the two holes below S1,
making sure that the positive (red) lead is inserted into the (+)
hole on the PC board.
❒82. The battery bracket may be attached in a variety of ways. A wire
jumper can be passed through the two holes on the PC board,
then both ends soldered on the underside of the board. You may
prefer to use very small screws or even a double-sided mounting
adhesive strip or glue. In using such methods, make sure that the
battery will not block the PC board's mounting hole in its vicinity.
Wiring of the PC board is now complete. If you have the the patience, we
suggest a short break. Then take a magnifying lens and a bright light and
examine all your solder joints, touching up any connection which appears
less than perfect. Make sure all excess leads have been trimmed, and
that one is not bent back flat against the board, possibly causing a short.
Brush the solder side of the board with a stiff brush to make sure that no
loose wire trimmings or solder drippings (tsk tsk) are lodged between
connections.

FR-10 •20
TESTING, ALIGNMENT AND ADJUSTMENT
To prepare the FR10 FM VHF Receiver for reliable monitoring operation,
you will need these basic tools:
1. A useful 10 meter signal source.
2. Hexagonal, non-metallic coil slug alignment tool for L3.
3. Small screwdriver to adjust L4.
1. Signal source: This signal can be from your test bench equipment or
from a "live" source such as a local repeater. The "live" signals are best
for fine-tuning, but they also have that VHF communications character of
being fast and to the point. Good test bench signal sources include your
own 10-meter transceiver, if you are licensed to use it, a signal
generator or grid-dip oscillator.
2. L3 Alignment Tool: If you do not already have a set of plastic or
nylon coil alignment tools and do expect to try further Ham radio or
electronic hobby projects, such tools are worth having and can be found
inexpensively at any electronics store including Radio Shack. While a
metal Hex key wrench can fit the coil slug, the metal itself would
damage the coil inductance drastically and therefore should not be used.
With patience and sandpaper, a useable tool might be formed from a
wood or plastic rod.