Check out the 6 meter action with this simple and fun to build
FM receiver. Receive crystal-clear signals from thousands of
miles away! Six meters is a fascinating band! Tune the entire 6
Meter band or the VHF low Police and Fire band.
•Tunes any 5 MHz portion of the 40 to 60 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
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.
FR-10 10 METER FM RECEIVER KIT INSTRUCTION MANUAL
Ramsey Electronics publication NO. MFR6 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.
FR6 • 2
Ramsey Publication No. MFR6
Price $5.00
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
FR6 6 METER
FM RECEIVER KIT
TABLE OF CONTENTS
I
ntroduction to the FR6 .................. 4
Circuit Description ......................... 5
Parts List ........................................ 6
Simplified Block Diagram .............. 8
Parts Layout Diagram .................... 9
Schematic Diagram ....................... 10
FR6 Assembly Instructions ........... 11
Testing and Alignment ................... 18
Enclosure Ideas ............................. 20
Troubleshooting Guide .................. 21
Notes for Advanced Users ............ 22
Ramsey Kit Warranty .................... 23
FR6 • 3
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
www.ramseykits.com
INTRODUCTION
FM and repeaters on 6 meters? You bet!
There's not a lot to say about using the FR6 receiver once its been correctly
built and aligned. If 6 meters is "dead”, it resembles the usual 2 meter action.
If 6 meters is "hot", you’ll find an amazing variety of crystal-clear FM signals
from many thousands of miles away! If there are local 6 meter repeaters in
your area, the FR6 will be just as active as the local repeater gang.
Since the FR6 “hears” only FM, the various SSB and CW signals on the band
will not be properly demodulated as to be intelligible.
This receiver is a good project for amateurs wishing to become more familiar
with 6 meter FM before choosing a transceiver, or for those active on 6 who
want an inexpensive receiver to take on trips, keep in a briefcase or to watch
for band openings.
Most Ramsey Electronic Kits 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 FR6 FM Receiver is
best regarded as a "Skill Level 2" project, (or least Level 1.46!) 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 Six 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 FR6, but we are
confident that you can construct the FR6 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 diodes. And,
in addition to four inductors, a 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.
FR6 • 4
BUILDING YOUR FR6 KIT
There are just over 200 solder connections on the FR6 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.
FR6 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) mixerproduct detector-oscillator. The tuneable 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 50-54 MHz signals, the oscillator must tune 60.7
to 64.7 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
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
FR6 • 5
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 .15 uH inductors [looks like a resistor with brown-green-silver
4 62 pF (C3,4,9,10)
4 100 pF [marked 100, 101, or 101K] (C6,11,12,22)
1 220 pF [marked 220 or 221] (C18)
6 .001 uF [marked .001 or 102 or 1 nF] (C7,8,20,23,24,25)
8 .01 uF [marked .01 or 103 or 10 nF] (C13,16,17,21,26,28,29,31)
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
NOTE CONCERNING THE AUDIO OUTPUT JACK
Your receiver kit is supplied with a standard subminiature 2.5 mm (3/32")
audio output 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 to rough up the PC board to accommodate your jack.
FR6 • 7
FR6 BLOCK DIAGRAM
U2, 3359
FR6 • 8
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