2 METER FM 5 WATT
TRANSMITTER KIT
Ramsey Electronics Model No. FT146
Here's a simple hard-working transmitter that's ideal for
repeaters, Fox-hunts, remote bases, Packet - you name it! Why
tie up a whole transceiver to just use the transmitter? Fun and
educational to build - you'll be on-the-air in an evening!
• Direct, true FM for excellent voice and data quality.
• Both Data and mike audio inputs
• Solid 5 watt RF output - add our PA-146 for 40 watts
• Crystal controlled with 146.52 MHz crystal included
• Built-in test points for easy tune-up. Align with any
digital multimeter - tuning tool included, too!
• Runs on 12 - 14 Volts DC at less than 1 amp
• Easy assembly and hook-up
• 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!
FT146 • 1
RAMSEY TRANSMITTER KITS
• FM10, FM-25 FM Stereo Transmitters
• TV6 Television Transmitter
• Cube TV Transmitters
RAMSEY RECEIVER KITS
• FR1 FM Broadcast Receiver
• AR1 Aircraft Band Receiver
• SR2 Shortwave Receiver
• AA7 Active Antenna
• SC1 Shortwave Converter
RAMSEY HOBBY KITS
• RB1 Rat Blaster Rodent Repeller
• SS70A Speech Scrambler
• TT1 Telephone Recorder
• WEB1 Walking Electronic Bug
• MD3 Microwave Motion Detector
• TFM3 Tri-Field Meter
• ECG1 Heart Monitor
RAMSEY AMATEUR RADIO KITS
• DDF1 Doppler Direction Finder
• HR Series HF All Mode Receivers
• QRP Series HF CW Transmitters
• FR146 2 Meter Receiver
• 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.
FT146 FM RECEIVER KIT INSTRUCTION MANUAL
Ramsey Electronics publication NO. MFT146 Rev. 1.3
First printing: February 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.
FT146 • 2
Ramsey Publication No. MFT146
Price $5.00
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
FT146 FM RECEIVER
KIT
TABLE OF CONTENTS
I
ntroduction to the FT146 .............. 4
Circuit Description ......................... 5
Parts List ........................................ 6
FT146 Assembly Instructions ........ 8
Testing and Alignment ................... 19
Power Supply Considerations ....... 21
Verifying RF Power Output ............ 21
Troubleshooting Guide .................. 23
Enclosure Ideas ............................. 24
Microphone Considerations ........... 24
Crystal Requirements .................... 25
Parts Layout Diagram .................... 26
Ramsey Kit Warranty ..................... 27
FT146 • 3
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
www.ramseykits.com
INTRODUCTION
Two meter FM has been around for years, but never with the popularity that
is enjoyed today. In the old days, hams snooped around the local two-way
radio shop in search of an obsolete taxi cab or police radio. These radios
were in the 150 - 174 MHz business band and were easily moved down into
the ham two meter band. On the chance that a UHF 450 - 470 MHz radio
was found, it was modified for the ham 440 band. Since there was no
business band near the 220 MHz ham band, no radios were available for
conversion - and that's why the 220 band never became popular!
Well, its been a long step from then to now, and not a pleasant one for ham
radio. We've lost a portion of our 220 band and gave up our ham radio
market to the Japanese. Gone are the radio mavens who could modify, in an
evening, the old Motorolas, GEs and RCAs. Modern day hams don't use
modified commercial radios, they operate rigs designed expressly for
amateur use, and who can blame them? For a half a kilobuck (that's $500 in
regular talk) you can get a full band synthesized 30 watt radio that looks like
a fine piece of audio gear! Good deal but something is missing, and that's the
pride in building, understanding and learning. You see it really doesn't take a
whole lot of smarts to unpack a box that was last sealed somewhere in the
Orient. Building your own rig is one of the most satisfying and rewarding
experiences you can have - and that's what ham radio is all about! This little,
easy to understand two meter FM transmitter is our attempt to provide the
ham community with a simple, fun to build kit that you'll enjoy operating,
especially when you tell the other operator that the rig here is home-brew.
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 FT146 FM
Transmitter 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 Two Meters and its maze of repeaters
holds, which means this could be your very first kit project. To be honest,
we'd like to see first-time builders start out with an easier kit such as the
Ramsey HR-40 forty meter all-mode receiver before assembling the FT146,
but we are confident that you can construct the FT146 successfully if you
follow this manual carefully and patiently.
Before beginning the project or even studying the circuit description, it's
worthwhile to develop some prior respect for how much transmitter is packed
onto the circuit board. The dozen semiconductor devices (diodes, transistors
FT146 • 4
and IC chip) give the equivalent of about 130 or more transistors and diodes.
And, in addition to 13 inductors, a crystal and the various plus and jacks, there
are over 60 capacitors and resistors. Surely, all that should result in a decent
transmitter! 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.
FT146 CIRCUIT DESCRIPTION
Basic overview: The FT146 is a crystal controlled FM transmitter that uses a
varactor modulated crystal oscillator followed by a 9 times frequency multiplier
and power amplifier. Test points are built-in for easy alignment.
Detailed description: Transistor Q1 functions as a Colpitts crystal oscillator
whose frequency is determined by Y1 and varactor diode D1. Transistor Q2
functions as a buffer amplifier to isolate the crystal oscillator from other portions
of the circuit. The crystal oscillator frequency is multiplied by 3 (tripled) in
transistor Q3. Frequency multipliers are nothing more than amplifiers that
produce lots of distortion! In this case we're interested in having enough
distortion so that the third harmonic is fairly strong. We "pick-off" or filter the
third harmonic with a band pass filter, comprised of L9,13 and capacitors
C28,21,22,16. This allows transistor Q4 to be driven only by the third harmonic
of the crystal frequency - in this case, around 48 MHz. Q4 is another tripler,
multipling up the 48 MHz to 144 MHz. Inductors L5,11 and capacitors
C25,17,18,10 for the band pass filter for the three times output frequency.
From here on out, we're working at the actual carrier frequency and use a
couple of transistors to amplify the signal up to a 4 to 6 watt level. Transistor Q5
boosts the signal to the 250 mW range and Q6 then produces the full power
output. Impedances must be matched between stages to allow for maximum
power transfer, and that's the function of a couple of coils that are hand wound.
A low pass filter follows the final amplifier to limit out of band signals (remember
those multiplier stages?). Modulation is accomplished by varying the
capacitance of varactor diode, D1. This varying capacitance shifts the frequency
of the crystal ever so slightly causing a frequency shift, which is FM or
Frequency Modulation. And yes - this frequency shift does get multiplied as it
travels through the multiplier stages. The signal used to vary the varactor diode
is our desired audio modulation. Op-amp U1 functions as a microphone
amplifier, clipper and low pass filter. We clip the microphone signal to prevent
overmodulation and limit the maximum modulation frequency since either one
could cause our transmitter to "splash" into adjacent channels.
To make our transmitter compatible with standard ICOM/YAESU style
microphones we use transistor Q7, which senses when current is being drawn
by the microphone. When the mike is keyed, the current drawn turns on Q7
which applies bias to transistor Q1, allowing it to operate and thus the rig goes
FT146 • 5
into transmit. There is no need to control the voltage to any other transistors
since they a
ll operate class "C". A class C amplifier draws no current unless it is
driven, so there is no need to switch the later stages on and off.
FT146 2 METER FM TRANSMITTER KIT PARTS LIST
Capacitors:
❒ 1 2 or 2.2 pf disc capacitor (marked 2 or 2.2 or 2K or 2.2K) [C17]
❒ 1 4.7 or 5 pf disc capacitor (marked 4.7 or 5 or 4.7K or 5K) [C21]
❒ 2 10 pf disc capacitor (marked 10 or 10K) [C19,20]
❒ 1 12 pf disc capacitor (marked 12 or 12K) [C25]
❒ 1 15 pf disc capacitor (marked 15 or 15K) [C27]
❒ 1 22 pf disc capacitor (marked 22 or 22K) [C18]
❒ 3 39 pf disc capacitor (marked 39 or 39K) [C13,15,28]
❒ 2 47 pf disc capacitor (marked 47 or 47K) [C10,22]
❒ 1 56 pf disc capacitor (marked 56 or 56K) [C14]
❒ 6 100 pf disc capacitor (marked 100 or 101) [C6,11,16,24,26,29]
❒ 1 470 pf disc capacitor (marked 470 or 471) [C30]
❒ 13 .001 uf disc capacitor (marked .001 or 1000 or 102)
[C7,8,23,31,32,33,37,38,39,40,41,44,45]
❒ 6 .01 uf disc capacitor (marked .01 or 10 nf or 103) [C1,3,4,5,35,36]
❒ 1 .1 uf disc capacitor (marked .1 or 104) [C9]
❒ 2 10 uf electrolytic capacitor [C34,42]
❒ 1 100 to 220 uf electrolytic capacitor [C2]
❒ 2 Trimmer capacitor, 30 pf [C12,43]
Resistors and potentiometers:
❒ 1 2 ohm resistor (red-black-gold) [R6]
❒ 1 51 ohm resistor (green-brown-black) [R10]
❒ 1 100 ohm resistor (brown-black-brown) [R28]
❒ 2 270 ohm resistor (red-violet-brown) [R8,20]
❒ 2 470 ohm resistor (yellow-violet-brown) [R7,25]
❒ 7 1 K ohm resistor (brown-black-red) [R1,2,4,9,11,22,29]
❒ 2 2.2 K ohm resistor (red-red-red) [R21,24]
❒ 6 10 K ohm resistor (brown-black-orange) [R12,15,16,23,26,27]
❒ 3 47 K ohm resistor (yellow-violet-orange) [R3,5,17]
❒ 3 100 K ohm resistor (brown-black-yellow) [R14,18,19]
❒ 1 5 K ohm potentiometer [R13]
FT146 • 6
Inductors and ferrite cores:
❒ 2 Shielded can tunable inductor (marked 007007) [L9,13]
❒ 2 Tunable inductor (pink plastic body) [L5,11]
❒ 2 6 hole ferrite bead core [L1,6]
❒ 2 Small ferrite bead core [L10,12]
❒ 2 Aluminum coil shield cans [for L5,11]
Semiconductor devices:
❒ 1 1N4002 style black epoxy diode [D5]
❒ 2 1N4148 style signal diode (glass body with black band) [D2,4]
❒ 1 BB609 varactor diode (black body with yellow color band) [D1]
❒ 1 Zener diode, 6.2 volt (gray body with black band) [D3]
❒ 2 2N3904 NPN transistor (marked 2N3904) [Q1,2]
❒ 1 2SC2498 or 2SC2570A VHF/UHF NPN transistor (marked C2498 or
2570A) [Q3]
❒ 1 NE021 flat pack NPN transistor (marked 021) [Q4]
❒ 1 2N3866 metal can NPN transistor [Q5]
❒ 1 SD1127 metal can RF power transistor [Q6]
❒ 1 2N3906 style PNP transistor (marked 221334) [Q7]
❒ 1 LM358 dual op-amp IC chip [U1]
❒ 1 LED Light emitting diode [LED1]
Special components:
❒ 1 Crystal 16.280 MHz (for 146.520 MHz output) [Y1]
❒ 1 5 pin DIN connector [P1]
❒ 1 RCA style phono jack [J1]
❒ 1 2.5MM sub-miniature phono jack [J2]
❒ 1 Push-on aluminum heat sink
❒ 1 5/16" x 20 bolt (to wind coils on)
❒ 1 1/2 feet enameled magnet wire
❒ 1 1/2 feet tinned buss wire
Required, not supplied:
❒ 12 volt DC power source at 1 amp minimum
❒ Microphone
❒ Dummy load or suitable antenna
❒ Enclosure such as the Ramsey CFT
FT146 • 7
RAMSEY Learn-As-You-Build KIT ASSEMBLY:
There are over 200 solder connections on the FT146 printed circuit board. That
means your work could be 99% perfect 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 CW HF 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 transmitter!
• 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.
We have a two-fold "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, follow the PC board drawing and the written direc
tions for all parts - especially when 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" the excess component lead wire 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. Install J1, the RCA-style antenna jack. Solder all 4 points.
❒ 2. Install P1, the 5 pin DIN jack.
FT146 • 8
❒ 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 R13, 5K trimmer pot. This is the modulation adjustment control.
❒ 5. Install U1, LM358 op-amp IC chip. In installing the 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 being able to
easily replace the IC if ever necessary. However, please be aware that we
have seen more service problems with improper socket insertion than from
soldering in 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 orient the end marked
by a band or dot correctly. Before soldering, make sure that the IC or
socket is perfectly flat against the top of the PC board and that all pins are
properly in each PC board hole. This little 8 pin chip contains two separate
amplifiers and is used to amplify the microphone output and process the
audio for transmisssion.
❒ 6. Install C39, .001 uf disc capacitor (marked .001, 1 nf or 102).
❒ 7. Install C38, .001 uf disc capacitor (marked .001, 1 nf or 102).
❒ 8. Install C36, .01 uf disc capacitor (marked .01 or 10 nf or 103).
❒ 9. Install R14, 100K ohm (brown-black-yellow).
❒ 10. Install R18, 100K ohm (brown-black-yellow).
❒ 11. Install R19, 100K ohm (brown-black-yellow).
❒ 12. Install C41, .001 uf disc capacitor (marked .001, 1 nf or 102).
❒ 13. Install R20, 270 ohm (red-violet-brown).
❒ 14. Install C42, 10 uf electrolytic capacitor. Electrolytic capacitors are
polarized with a (+) and a (-) lead and must be installed in the correct
orientation. Ordinarily, only the negative side is marked on the capacitor
body with a dark band and the (-) sign clearly shown, while PC boards will
usually show the (+) hole location. Use care to ensure proper polarity.
❒ 15. Install JMP2, jumper wire. Use a piece of wire clipped from a previously
installed component bent into a small "U" or wire staple shape. Jumpers act
as electronic "bridges" carrying signals over PC board traces underneath.
❒ 16. Install another wire jumper, JMP1.
❒ 17. Install C34, 10 uf electrolytic capacitor. Remember to observe correct
polarity.
❒ 18. Install C37, .001 uf disc capacitor (marked .001, 1 nf or 102).
❒ 19. Install R17, 47 K ohm (yellow-violet-orange).
❒ 20. Install C40, .001 disc capacitor (marked .001, 1 nf or 102).
FT146 • 9
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