Ramsey FHT1 User Manual
Sly Fox
FOX-HUNT
TRANSMITTER KIT
Ramsey Electronics Model No. FHT-1
Get involved in the fox hunting fun! This kit combines a
crystal locked true FM transmitter with a microprocessor
for reliable operation. Multiple transmission “modes”
assure a “sly fox” that will challenge any fox hunter.
• Selectable high (5W) or low power (800 mW) operation - unit can
even be programmed to change power levels during use!
• Delay times from one minute to one hour !
• Stable crystal operation with a 146.52 crystal included.
• Sixteen modes of operation available. Can even generate a 1 KHZ
tone to “fool” Doppler type direction finders!
• Fully microprocessor controlled for easy use, no diodes to add.
Easy and fun to use!
• Smartkey CW ID input - just key your call in and it remembers!
• Runs on 12 - 14 Volts DC at less than 1 amp.
• Built in test points for tune up. Align with any digital multimeter -
tuning tool included, too!
• Add optional electronic VOICE ID CIRCUIT for harassment
messages - up to 20 seconds, “Ha, ha you can’t find me!”
• Informative manual answers questions on theory, hookups and
uses - enhances resale value, too!
FHT-1 • 1
RAMSEY TRANSMITTER KITS
• FM-10, FM-25 FM Stereo Transmitters
• FM-1,2,4 FM Wireless Microphones
• PB-1 Telephone Transmitter
RAMSEY RECEIVER KITS
• FR-1 FM Broadcast Receiver
• AR-1 Aircraft Band Receiver
• SR-1 Shortwave Receiver
• AA-7 Active Antenna
• SC-1 Shortwave Converter
RAMSEY HOBBY KITS
• SG-7 Personal Speed Radar
• SS-70 Speech Scrambler
• TT-1 Telephone Recorder
• SP-1 Speakerphone
• MD-3 Microwave Motion Detector
• PH-10 Peak hold Meter
• LC-1 Inductance-Capacitance Meter
RAMSEY AMATEUR RADIO KITS
• FX Series VHF and UHF Transceivers
• HR Series HF All Mode Receivers
• QRP Series HF CW Transmitters
• CW-7 CW Keyer
• PA Series VHF and UHF Power Amplifiers
• Packet Computer Interfaces
• 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.
FHT-1 FOX-HUNT TRANSMITTER KIT INSTRUCTION MANUAL
Ramsey Electronics publication No. MFHT-1 Revision 1.1
First printing: October 1993
COPYRIGHT 1993 by Ramsey Electronics, Inc. 793 Canning Parkway, 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.
FHT-1 • 2
Ramsey Publication No. FHT-1
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
SlyFox FOX HUNT
TRANSMITTER KIT
TABLE OF CONTENTS
Introduction to the FHT-1 .............. 4
How it works .................................. 5
Parts list ........................................ 6
FHT-1 Assembly instructions ........ 8
Parts Layout diagram .................... 9
Schematic diagram ..................... 18
Initial testing ................................ 21
Programming ............................... 24
Troubleshooting ........................... 28
Ramsey kit warranty ................... 31
Price $5.00
FHT-1 • 3
RAMSEY ELECTRONICS, INC.
793 Canning Parkway
Victor, New York 14564
Phone (716) 924-4560
Fax (716) 924-4555
INTRODUCTION
Finding a small, hidden radio transmitter may seem fairly easy at first, but
with a sly transmitter the hunt can be made very challenging! With the
interest in radio foxhunting on the rise, the need arose for a low cost
transmitter to be used as the radio “fox” for the hunt! The problem is trying to
configure a HT or converted commercial band transmitter to key at different
times, ID itself, and perhaps leave a brief message. By the time all these
components are assembled together, a small fortune is usually invested in
radios, timers, and ID’ers with a good deal of interconnection necessary.
What’s really needed is an inexpensive portable transmitter with all these
options built in, and that's why the FHT Fox Hunt Transmitter was created.
Also, 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 at a
fox hunt, especially when you tell the other operators that the fox rig is a
home-brew.
Most Ramsey Electronics 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 FHT-1 Fox-hunt
Transmitter is best regarded as a "Skill Level 2" project, and should not be
taken lightly, even by experienced, licensed radio amateurs. Still, this stepby-step manual is written with the beginner in mind, because we are well
aware of the fascination fox hunting 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 FHT-1, but we are confident that you can construct
the FHT-1 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
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 plugs 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.
FHT-1 • 4
FHT-1 CIRCUIT DESCRIPTION
Basic overview: The FHT-1 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. The
“brains” of the unit is a Motorola microcontroller programmed to remember
your CW ID and to control transmit power and timing.
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 "pickoff" 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, multiplying up the 48 MHz to 144 MHz. Inductors L5,11 and
capacitors C25,17,18,10 form a 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. There is no need to
control the voltage to any other transistors since they all 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.
The microcontroller U2 contains the programming to control the transmitter’s
functions . When in programming mode, the chip is enabled to remember the
CW ID that is “sent” to it via the Paddles input. The four DIP switches can be
set to run one of sixteen different programs controlling on and off times and
power levels, including one user-programmable mode.
FHT-1 • 5
FHT-1 FOX-HUNT TRANSMITTER KIT PARTS LIST
Resistors and potentiometers:
1 2 ohm resistor (red-black-gold) [R6]
2 47 ohm resistors (yellow-violet-black) [R18,19]
1 51 ohm resistor (green-brown-black) [R10]
2 100 ohm resistor (brown-black-brown) [R28,40]
1 270 ohm resistor (red-violet-brown) [R8]
2 390 ohm resistors (orange-white-brown) [R33,34]
3 470 ohm resistors (yellow-violet-brown) [R7,16,20]
9 1K ohm resistors (brown-black-red) [R1,2,4,9,12,21,22,29,31]
1 2.2K ohm resistor (red-red-red) [R15]
1 4.7K ohm resistor (yellow-violet-red) [R47]
11 10K ohm resistors (brown-black-orange)
[R14,17,23,36,37,38,39,43,44,45,46]
2 47K ohm resistors (yellow-violet-orange) [R3,5]
1 200 ohm potentiometer (marked 201) [R41]
1 5K potentiometer (marked 502) [R13]
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]
1 150 pf disc capacitor (marked 150 or 151) [C48]
1 470 pf disc capacitor (marked 470 or 471) [C30]
6 .001 uf disc capacitor (marked .001 or 1000 or 102)
[C7,8,23,31,32,44]
9 .01 uf disc capacitor (marked .01 or 10 nf or 103)
[C1,3,4,5,33,39,40,49,50]
3 .1 uf disc capacitor (marked .1 or 104) [C9,35,36]
4 10 uf electrolytic capacitor [C41,45,53,54]
2 100 to 220 uf electrolytic capacitor [C2,34]
2 Trimmer capacitor, 35 pf [C12,43]
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]
FHT-1 • 6
2 Small ferrite bead core [L10,12]
2 Aluminum coil shield cans [for L5,11]
Semiconductor devices
1 1N4002 style black epoxy diode [D9]
3 1N4148 style signal diode (glass body with black band) [D2,4,5]
1 FS4059 varactor diode (black body with yellow color band) [D1]
1 Zener diode, 6.2 volt (gray body with black band) [D3]
3 2N3904 NPN transistor (marked 2N3904) [Q1,2,7]
1 2SC2498 or 2570 VHF/UHF NPN transistor [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 2N5193 PNP transistor (marked 2N5193) [Q8]
1 7805 voltage regulator IC (marked 7805) [VR1]
1 68HC705K1 microcontroller IC (marked FHT1)
2 LED Light emitting diode [D7,8]
Special components
1 Crystal 16.280 MHz (for 146.520 MHz output) [Y1]
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 ½ foot enameled magnet wire (#28)
1 ½ foot tinned buss wire (#20)
1 FHT epoxy printed circuit board
1 Low Pass Filter printed circuit board
1 SPDT Slide switch [S2]
1 4 pin DIP switch[S3]
1 16 pin IC socket
1 SO 239 chassis mount connector
2 #4-40 screws, 1/2” - 5/8” in length
4 #4-40 nuts
1’ black jacketed wire (#18)
1 1’ red jacketed wire with fuseholder
Required, not supplied
12 volt DC power source at 1 amp minimum
Dummy load or suitable antenna
Enclosure such as the Ramsey CFHT
FHT-1 • 7
RAMSEY Learn-As-You-Build KIT ASSEMBLY
There are over 200 solder connections on the FHT-1 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
directions 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!
FHT-1 • 8
FHT-1 PC Board component placement diagram
Shaded Parts used in Voice ID option
External Switch
S1
connections
(opt)
To
Low
Pass
LED 1
LED 2
Board Filter
short
leads
TEST
Connection
s
-
+
Micro
Battery
Backu p
Ground
Jumpers
TP3
FHT-1 • 9
Long Lead
for
mounting
C7
1. Install J2, the subminiature phone jack.. Gently push the solder tabs
through the PC board being careful not to bend or strain them. Solder all
three tabs.
2. Install R41, 200 ohm trimmer pot (marked 201). This is the audio
output or volume control.
3. Install R40, 100 ohm (brown-black-brown). This completes your
earphone monitor output for the transmitter.
4. Install diode D9, the 1N4002 type (black body with a silver band). Be
sure to observe the correct polarity! See the parts placement diagram for
correct orientation.
5. Install C54, 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.
6. In the same manner, install another 10uF electrolytic capacitor in the
C53 position. See the parts placement diagram for correct orientation.
7. Install voltage regulator VR1, marked 7805. Observe the correct
placement of the metal tab. Mount it so that the lettering on the device
faces toward capacitor C53 and jack J2. This IC provides a stable
source of 5 volts for the digital sections of the circuit.
8. Install the LED’s (light emitting diodes) D8 and D7. Being diodes,
these components are polarized and must be installed with regard to
their polarity. Identify the cathode (or - lead) side lead which is the
shorter of the two component leads, and is usually marked with a “flat”
notch on the plastic body of the LED. These leads should face toward
the outside of the PC board as shown in the parts placement diagram.
9. Install R34, 390 ohm (orange-white-brown). Notice that this resistor
is “standing up” on the circuit board.
10. Install R33, 390 ohm (orange-white-brown) in the same manner.
11. Install R36, 10K ohm (brown-black-orange).
12. Install C50, .01 uF disc capacitor ( marked .01 or 103 or 10nF).
13. Install R39, 10K ohm (brown-black- orange).
14. Install C49, .01 uF (marked .01 or 103 or 10nF).
15. Install R38, another 10K (brown-black-orange).
16. Install R37, yet another 10 K (what colors were those?!) (brown-
FHT-1 • 10
black-orange).
17. Install R21, 1K ohm (brown-black-red).
18. Install C39, .01uF disc cap (marked .01 or 103 or 10nF).
19. Next we’ll install switch S2 (the run - program switch for the
microprocessor). Gently slide the six solder pins through the PC board
for connection. Solder all six connections. Use enough heat to “flow” the
connections, especially on the ground “plane” connections.
20. Install C45, 10 uF electrolytic. Be sure to observe the correct polarity.
See the parts placement diagram for correct orientation.
21. Install JMP7, 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.
22. Install another wire jumper, JMP3.
23. Install resistor R23, a 10K ohm (marked brown-black-orange). Note
that this is a “stand up” component, so follow the parts placement
diagram.
24. Install R20, 470 ohm (yellow-violet-brown).
25. Install C36, 0.1 uF disc cap (marked .1 or 104).
26. Form and install jumper JMP1. This completes the audio path from
the microcontroller IC to the FM transmitter section of the unit. If you
have purchased the voice ID option, the accompanying FHID-1 manual
will direct you in the proper steps to take concerning JMP1 and
associated components.
27. Now that your soldering skills have been warmed up, we’ll install the
16 pin IC socket in the U2 position. We provide this socket because
many people feel it is easier to install a socket than to risk damaging the
IC chip while installing it. However, please be aware that we have seen
more service problems with improper socket insertion than from
soldering in ICs. Make sure that the IC socket is perfectly flat against the
PC board before soldering, and pay extra attention to not “bridge” or
splash solder between pads or traces while installing this socket. Do not
install the microcontroller yet, we’ll do that while we’re testing!
28. Next, install resistors R43,R44, R45, and R46 which are all 10K ohm
(brown-black-orange). These are “pull down” resistors, that is, they “pull”
the corresponding pins of U2 to ground potential unless one of the
switches contained in S3 is turned on. These resistors insure a good
logic zero or one condition for the microcontroller.
29. Install the DIP switch, S3. This “switch” looks like an eight pin IC - it
FHT-1 • 11
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