HAMTRONICS TD-5 Owner's manual

©2009 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. evised:
10/28/10
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 CAUTION. The TD-5 contains
static sensitive ic's, which require nor-
mal static prevention techniques when
handling to avoid damage. Wearing a
grounded wrist strap is a prudent prac-
tice. For wired units, do not remove the
unit from its protective package until
read to install. For kits, do not open
package with semiconductors until
read to install on board.
FUNCTIONAL DESCRIPTION.
The TD-5 is a general purpose CTCSS En-
coder and Decoder module designed with en-
hanced features to allow it to be used in
repeater control. It is crystal controlled for
precise tone accuracy and is easily tunable by
setting a DIP switch to co er the entire range
of subaudible tone frequencies from 67 to 254
Hz. Its CMOS circuitry operates on +7 to 15
Vdc, drawing only 7 mA!
As a general purpose tone encoder, you
can easily adapt your existing fm transcei er
to access all your fa orite closed repeaters. If
you only need one tone, you can select it with
the DIP switch on the module. If you need
se eral tones, the manual shows how you can
set up a front panel switch to select between
preset tones for se eral repeaters. A pot on
the board allows you to set the transmitter
de iation for the tone separately from your
microphone audio.
As a general purpose receiver decoder,
the same TD-5 can be used to mute recei e
audio unless the proper subaudible tone is
present on the signal. A con enient control
line can be used to manually unmute the re-
cei er to allow monitoring the channel when
desired, and a high pass filter gets rid of an-
noying tone buzz in the speaker audio. Unlike
many such units, the TD-5 module handles
both encode and decode! When used in a
transcei er, your ptt line can be connected to
the unit to switch between transmit and re-
cei e modes.
The TD-5 was designed especially to have
the added features needed to provide closed
access for your repeater. To block repeater
transmission unless the user signal has the
proper subaudible tone, an output transistor
grounds the COS line between the recei er
and the control board to pre ent it from rec-
ognizing that the squelch is open. The TD-5
pro ides remote on/off capability when used
with a DTMF controller. Whene er you need
to defeat the TD-5 and allow anyone to access
the repeater, simply ground the control line
with any touch tone controller and the re-
peater becomes an open repeater.
It can also be used as a repeater tone en-
coder. Most repeaters use CTCSS only on re-
cei e. But if you need to transmit a
subaudible tone as well, it is a simple matter
of connecting the tone output of a second TD-
5 module to the modulator input of your ex-
citer. There is a handy tone output le el con-
trol to set the transmitter de iation.
CAUTION.
The TD-5 kit contains static sensiti e
ic's, which require normal static pre ention
techniques, such as wrist strap and grounded
soldering iron to a oid damage. Do not re-
mo e the ic from its protecti e package until
so instructed.
The kit also requires soldering a small
surface mount ic to the pc board. If you don't
feel you can do these operations properly,
you may want to seek help from someone
more experienced or exchange the unit for a
wired/tested module.
THEORY OF OPERATION.
Refer to the schematic diagram.
The heart of the unit is the MX-465DW ic,
which pro ides encoding and decoding of all
standard subaudible tones. Pins 2 and 3 op-
erate in a 4 MHz crystal oscillator circuit. Pins
5-10 are control lines which select the fre-
quency, and pull up resistors are pro ided in
the chip. Frequency selection normally is
done with the DIP switch on board, but it can
also be done with an external circuit placing
grounds on selected lines using a front panel
switch and a diode matrix arrangement. Pin
17 controls whether the ic is operating in the
transmit or recei e mode at any time.
Pin 24 is the input for the tone detector.
If the audio present contains the proper
subaudible tone, RX Detect line pin 15 goes hi.
The output of this detector is integrated to
pre ent bouncing and falsing by C6. The turn
on time constant is set with R4 and R5-D2 in
conjunction with C6. The turn off time is set
by R4 and C6. The integrated signal is applied
to a comparator at pin 14, and the switched
output is the RX Decode signal at pin 13.
The RX Decode output is used to turn Q1
on and off, and the transistor is used to inhibit
the COS line going to a repeater controller,
such as our COR-5 module, thus pro iding
closed access repeater operation. The Defeat
line at E5 pro ides a way for a touch tone con-
trol circuit to defeat the COS Inhibit function
when desired.
The RX Decode signal also switches the
audio path between pins 23 and 19. Between
these two pins is a switched capacitor high-
pass filter, which attenuates audio frequen-
cies below 250 Hz by about 36 dB while pass-
ing frequencies abo e 300 Hz. This can filter
can be connected in series with the audio
path in a recei er to remo e the buzz associ-
ated with subaudible tones and also to mute
the audio completely if the tone isn't present
on the rf signal. The Push To Listen (PTL) line
at pin 18 can be used to defeat the muting ac-
tion when you want to monitor the channel to
check for acti ity before transmitting.
When the RX/TX line at pin 17 is
grounded, the ic changes to the transmit
mode. In this mode, the switched capacitor
high-pass filter can be used in the transmit
audio path to remo e frequencies below 250
Hz from the signal. This feature normally is
not used in amateur radio applications, but in
transcei ers, it can be used to pre ent low
frequency speech components from falsing a
CTCSS decoder at the recei er hearing the
transmitted signal. When used, the audio line
is run through pins 22 and 20 to the modula-
tor in the transmitter.
ASSEMBLY.
GENERAL NOTES.
Construction is fairly simple. Refer to the
parts list and component location diagram,
and solder all parts in place, using short leads.
Following are some special points to consider.
a. The ic is static sensiti e. Suitable
precautions must be taken when handling, in-
cluding using a wrist strap and a grounded
soldering iron.
b. Resistors and diodes mounted erti-
cally are shown with the body of the resistor
designated by a circle.
c. Obser e polarity on electrolytic ca-
pacitors, diodes, transistor, and ic.
d. With modern CAD-produced pc
boards, pad sizes are smaller than what you
may be used to. Because the board has
plated-through holes, it is the solder inside
the hole, and not on the pad, which makes the
electrical connection.
Use solder sparingly. It helps to use a
small soldering tip and a minimal amount of
small-diameter solder. It also helps to work
under a magnifier lamp if you ha e one, espe-
cially for the ic.
e. Note that there is one hole in the
HAMTRONICS
®
TD
-
5 SUBAUDIBLE TONE EN
CODER/DECODER
:
ASSEMBLY, INSTALLATION, AND OPERATION

©2009 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. evised:
10/28/10
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board next to the crystal which has no lead
soldered to it. This is a " ia", which carries
ground through to pin 11 of the ic on the bot-
tom of the board. There are also many holes
which are used as terminals for connection to
the outside world, many of which are optional
and may not be used in your application. And
you will note that holes connected to the
ground plane are "thermals", a special pattern
which allows connection but minimizes
heatsinking to make soldering and unsolder-
ing easier.
CONSTRUCTION SEQUENCE.
a. The ic is soldered to the bottom of
the board with pin 1, identified by a dot in the
plastic mold, toward R6 and the leads for the
crystal. That would be the left end of the
board as shown in figure 2. Make sure you
ha e it oriented correctly before soldering.
Begin by tack soldering one corner and
readjusting until all the leads line up properly
with the tracks. Double check that you ha e
pin 1 connected to the trace running to U2
and C3. Then, tack solder the opposite corner
lead. Finally, solder all the other leads. If you
accidentally get solder between two leads,
drawing the iron between them away from
the ic should separate the two pads. If neces-
sary, use desoldering tool or wick to remo e
excess solder.
b. Turn the board o er and orient as
shown in the two top iews.
c. Install crystal o er ground plane as
shown, and solder leads to pads under board.
Lay crystal flat against ground plane, and tack
solder the top of the can to the ground plane
with a small bead of solder. This will be at the
right hand side of the crystal can as shown in
the top iew, and it will hold the crystal se-
curely in place.
d. Install the DIP switch with the switch
numbering running in the proper direction.
Solder all leads under board. If the switch
supplied is a 7-position switch; in this case, cut
off the leads for position 7 before mounting.
e. Install potentiometer R2 as shown
and solder leads. Be careful to elevate the pot
leads slightly to prevent the bases of the leads
from shorting to the ground plane.
f. Solder oltage regulator U2 and tran-
sistor Q1, with proper orientation.
g. Install electrolytic capacitors, obser -
ing polarity.
h. Install the other (ceramic and mono-
lithic) capacitors.
i. Install resistors and diodes, obser ing
diode polarity. See detail of diodes next to
top iew.
j. Check o er construction to be sure all
parts are installed in the proper holes with the
proper polarity. Check all solder joints for bad
joints, solder splashes, etc.
INSTALLATION.
GENERAL.
Installation consists of mounting the
module, selecting the tone frequency, pro id-
ing power, and making connections to the re-
quired circuits in the radio equipment. The
latter information is di ided into two major
sections: transcei er installation and repeater
installation; choose whiche er applies.
MOUNTING.
The TD-5 module is designed to be
mounted to the side wall of a radio chassis
with the pot and DIP switch at the top for easy
access, just below the upper edge of the box.
To locate the mounting holes, draw a line one
inch below the top of the box. Then, mark the
two mounting holes 1-7/8 inches apart on the
line. Attach the module with 4-40 screws and
standoffs or spacers as desired.
The usual location for the TD-5 module
used with the recei er in a Hamtronics
REP-200 Repeater is on the rear panel of the
enclosure near the recei e coax connector.
This is con enient for connections to the
feedthrough capacitors on the partition, and it
allows easy access to the pot and switch for
adjustment.
For transmit operation, the TD-5 usually is
mounted in the exciter compartment, on the
shield just to the right of the exciter. In many
transcei ers, you will probably be forced to
find any practical space where the module will
fit; you may e en ha e to mount it in a mini-
box attached to the rear of the radio.
SELECTING CTCSS FREQUENCY.
The tone frequency is selected by ground-
ing binary control lines (see D0 thru D5 on
schematic diagram). The ic has pullup resis-
tors; so ground = lo logic le el and open circuit
= hi. Table 1 shows the pattern of logic signals
required for each tone frequency.
DIP SWITCH METHOD.
If you only need one tone, you can select
it with the DIP switch on the module. Set the
six switch le ers according to the logic le els
indicated for the desired tone frequency in
Table 1. Open on the switch is logic 1 (hi) and
closed is logic 0 (lo).
FRONT PANEL SWITCH METHOD.
If you need se eral tones, for use in a
transcei er to access se eral repeaters, you
can set up a front panel switch to select be-
tween preset tones. To do so, you must re-
mo e the DIP switch or set all the le ers to the
open position. Then, connect diodes in a ma-
trix to the lines you need to ground for each
tone frequency.
Figure 1 shows such a matrix with three
sample tone frequencies. The diodes are nec-
essary to a oid shorting two lines together.
Connect diodes to ground the lines designated
for logic "0" in Table 1. Diode connections are
made at the pads normally used for S1 con-
nections to the ic data lines, i.e., the ic side of
the switch, not the ground side. Lines desig-
nated for logic "1" should be left open, as
there are pullup resistors in the ic.
HOW TO MAKE CONNECTIONS.
External connections to the module
should be made with #22 hookup wire sol-
dered to the terminal pads on the module.
Normally, only pads E1-E7 along the bottom
of the board are used; howe er, with certain
options, E8-E12 may also be used. Cut
hookup wires to length required for your in-
stallation, strip each end 1/4 inch, and then
solder one end to terminal pad on the board.
POWER CONNECTIONS
B+ for the unit is connected to E2. The
Table 1. DIP Switch Programming
(Note: 1 = open, 0 = closed)
Switch Pos →
→→
→1 2 3 4 5 6
67.0 Hz 1 1 1 1 1 1
69.3 Hz 1 0 0 1 1 1
71.9 Hz 1 1 1 1 1 0
74.4 Hz 0 1 1 1 1 1
77.0 Hz 1 1 1 1 0 0
79.7 Hz 1 0 1 1 1 1
82.5 Hz 0 1 1 1 1 0
85.4 Hz 0 0 1 1 1 1
88.5 Hz 0 1 1 1 0 0
91.5 Hz 1 1 0 1 1 1
94.8 Hz 1 0 1 1 1 0
97.4 Hz 0 1 0 1 1 1
100.0 Hz 1 0 1 1 0 0
103.5 Hz 0 0 1 1 1 0
107.2 Hz 0 0 1 1 0 0
110.9 Hz 1 1 0 1 1 0
114.8 Hz 1 1 0 1 0 0
118.8 Hz 0 1 0 1 1 0
123.0 Hz 0 1 0 1 0 0
127.3 Hz 1 0 0 1 1 0
131.8 Hz 1 0 0 1 0 0
136.5 Hz 0 0 0 1 1 0
141.3 Hz 0 0 0 1 0 0
146.2 Hz 1 1 1 0 1 0
151.4 Hz 1 1 1 0 0 0
156.7 Hz 0 1 1 0 1 0
159.8 Hz 1 0 0 0 1 1
162.2 Hz 0 1 1 0 0 0
167.9 Hz 1 0 1 0 1 0
173.8 Hz 1 0 1 0 0 0
179.9 Hz 0 0 1 0 1 0
183.5 Hz 0 1 0 0 1 1
186.2 Hz 0 0 1 0 0 0
189.9 Hz 1 1 0 0 1 1
192.8 Hz 1 1 0 0 1 0
196.6 Hz 0 0 1 0 1 1
199.5 Hz 1 0 1 0 1 1
203.5 Hz 1 1 0 0 0 0
206.5 Hz 0 1 1 0 1 1
210.7 Hz 0 1 0 0 1 0
218.1 Hz 0 1 0 0 0 0
225.7 Hz 1 0 0 0 1 0
229.1 Hz 1 1 1 0 1 1
233.6 Hz 1 0 0 0 0 0
241.8 Hz 0 0 0 0 1 0
250.3 Hz 0 0 0 0 0 0
254.1 Hz 0 0 0 1 1 1

©2009 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. evised:
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negati e supply normally is connected
through the mounting hardware to the chas-
sis, but E1 can be used for the ground connec-
tion if necessary. Since a 5V regulator is used
in the TD-5, B+ can be anything from 7 to
15Vdc. Current drain normally is only about 6
mA.
TRANSCEIVER INSTALLATION.
TRANSMITTING A CTCSS TONE.
The TD-5 can be used to transmit a CTCSS
tone to access closed repeaters or to operate
in a system with tone squelch which separates
users. The tone output le el is adjustable up
to 2V p-p (710 mV rms) into a high impedance
circuit. The le el will be somewhat lower with
a load because of the resistor in series with
the audio in the TD-5.
To add the CTCSS tone to your trans-
cei er, connect a hookup wire from E7 on the
TD-5 to the input of the modulator stage in
the exciter. The exact circuit for the connec-
tion must be determined for the particular ex-
citer you ha e.
It is important to inject the tone into the
modulator of the transmitter in a way which
bypasses the speech processing circuits for
the microphone, but at the same time does
not load down the audio coming from those
circuits. Normally, there will be a low-pass fil-
ter which allows the audio to be injected into
the modulator while keeping the oscillator rf
signal from getting out into the audio circuits.
This circuit normally is a series resistor and a
shunt capacitor.
To put the TD-5 in the transmit mode, you
must connect a jumper between E10 and E12.
This grounds the TX/RX control line.
If you want to use the same unit for
transmit and recei e operation in a trans-
cei er, you can connect E12 through a 1N4148
diode to the ptt line in the transcei er. This
assumes your ptt line is grounded to transmit.
The cathode should be connected to the ptt
line and the anode to E12.
RECEIVER AUDIO MUTING.
To mute the audio in the recei er when
no CTCSS tone is present, connect E3 and E4
in series with the audio path in the recei er
somewhere between the discriminator and
the deemphasis network, normally a series re-
sistor and a shunt capacitor right after the dis-
criminator output. This connection point
should be ahead of the squelch muting circuit
in the audio path. Consult the manual for
your recei er to find appropriate connection
point.
Input sensiti ity is such that any tone le el
between 125-2000 mV p-p is acceptable (45-
710 mV rms).
The muting circuit in the TD-5 also pro-
ides a high pass filter to eliminate any buzz
from the recei ed CTCSS tones.
If you want to be able to monitor some-
times when the proper CTCSS
tone is absent, you can use a
switch to control the ground
path to the PTL control line at
E11. To use this feature, you
must break the pc trace on the
rear of the board between E10
and ground.
REPEATER
INSTALLATION.
AUDIO INPUT.
Audio from the recei er
normally should be picked up
from the discriminator for con-
nection to E3. Later model Ham-
tronics® recei ers ha e a ter-
minal on the recei er for the discriminator
audio. On earlier models or on other brands
of recei ers which do not ha e a dedicated
terminal, the discriminator audio is accessible
at the resistor/capacitor junction of the de-
emphasis network. Consult the manual for
your recei er to find appropriate connection
point. Input sensiti ity is such that any tone
le el between 125-2000 mV p-p is acceptable
(45-710 mV rms).
REPEATER INHIBIT
CONNECTIONS.
An output transistor in the TD-5 pro ides
a ground at E6 when no tone is present and
an open circuit when the proper tone is re-
cei ed. In a repeater, this switched output
normally is used to inhibit the repeater by
grounding the COS signal from the recei er to
the COR board in the repeater. The easiest
place to connect is at the feedthrough capaci-
tor used to carry the COS signal through the
recei er partition.
If you wish to use touch-tone control to
disable the TD-5 and allow open access re-
peater operation, you will need to add an-
other feedthrough capacitor to the recei er
partition and a wire from the other side of the
ft cap to the auxiliary control output of a
touch-tone controller. In the recei er com-
partment, connect the control line from the
feedthrough capacitor to Defeat terminal E5
on the TD-5.
OPTION TO TRANSMIT ENCODED
TONE.
In most repeaters, it is unnecessary to re-
transmit the subaudible tone; it is only neces-
sary to inhibit the repeater if a station is heard
without the proper tone.
If you wish to ha e your repeater trans-
mit a CTCSS tone, do the following.
a. Add a TD-5 module near the exciter.
In the REP-200 Repeater, the TD-5 usually is
mounted in the exciter compartment, on the
shield just to the right of the exciter. Note
that the TD-5 cannot do transmit and recei e
modes at the same time; so a separate TD-5
must be used for transmit operation.
b. Connect a hookup wire from E7 on
the TD-5 to the input of the modulator stage
in the exciter. The exact circuit to connect to
must be determined for the particular exciter
you ha e.
For our TA51 ( hf) Exciter, connect to the
loop at the top of R22. This injects the audio
directly into the low pass filter at the input of
the modulator.
For our TA451 (uhf) Exciter, connect a 47K
resistor from E7 on the TD-5 o er to the lead
of C11 closest to de iation pot R15. This also
injects the tone into the modulator, but the
47K resistor pre ents loading of the circuit in
the uhf exciter.
For our synthesized exciters, connect to
the dedicated ctcss input terminal pro ided
on the exciter.
If you need to connect the tone to an-
other type of transmitter, use a similar ap-
proach. It is important to inject the tone into
the modulator of the transmitter in a way
which bypasses the speech processing circuits
for the microphone, but at the same time
does not load down the audio coming from
those circuits. Normally, there will be a low-
pass filter which allows the audio to be in-
jected into the modulator while keeping the
oscillator rf signal from getting out into the
audio circuits.
c. You must also connect B+ to E2 on
the TD-5 as explained earlier.
d. To set the TD-5 for transmit mode,
connect a jumper between E10 and E12. If
you want to be able to turn the transmitted
CTCSS tone off, you can connect a switch to
disconnect the ground when you do not want
the tone.
TRANSMIT LEVEL ADJUSTMENT.
TONE LEVEL control R2 on the TD-5 is ad-
justed for the desired de iation of the
subaudible tone. The TD-5 has a resistor (R3)
in series with its output to a oid loading down
the exciter audio circuits. The tone output
le el is adjustable up to 2V p-p (710 mV rms)
into a high impedance circuit. The le el will
be somewhat lower with a load.
D0
D1
D2
D3
D4
D5
1
2
3
4
5
6
U1
MX465DW
ROTARY SWITCH
77.0 HZ100.0 HZ
Figure 1. Example of Front Panel Selection Switch
S1 SWITCH
TERMINALS
118.8 HZ

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If TONE LEVEL control R2 pro ides too
high a le el, e en with it adjusted to a low set-
ting, additional resistance can be added in se-
ries with output terminal E7 or R3 can be
made larger.
Normally, the le el of the tone should be
set for about 300 Hz de iation. That is suffi-
cient for any normal decoder to detect.
(Good decoders normally decode anything
o er 50-100 Hz de iation.) Sometimes people
want to use much higher le els on tones, and
not only is this unnecessary but it causes the
tone to be heard as a buzz on the oice signal;
if set high enough, may e en ha e a detrimen-
tal effect on a touch-tone command system.
TROUBLESHOOTING.
GENERAL.
The circuit is relati ely simple. First, re-
read the theory of operation on page 1. Be-
cause all major functions of the unit are
performed in ic U1, troubleshooting is pretty
straight forward. An oscilloscope usually is
essential in troubleshooting, although it may
be possible to get by with just a oltmeter.
CURRENT CONSUMPTION.
The TD-5 can operate on any source of +7
to 15Vdc, and it normally draws about 6 mA.
AUDIO LEVELS.
The transmit tone output le el is adjust-
able up to 2V p-p (710 mV rms) into a high
impedance circuit. The le el will be some-
what lower with a load because of the resistor
in series with the audio in the TD-5.
Recei e input sensiti ity is such that any
tone le el between 125-2000 mV p-p is ac-
ceptable (45-710 mV rms). Output of the re-
cei e filter and switch circuit at E4 should be
about the same as the input le el.
VOLTAGE TESTS.
Table 2 gi es dc and oscillator oltages for
the main ic (U1) measured on a sample unit.
These readings are typical but may ary
somewhat. As always, such data should be
used in conjunction with a logical trouble-
shooting procedure to a oid jumping to con-
clusions if a oltage is a little different in your
unit. Some are dependent on being in either
transmit or recei e mode. Note that pins
used as logic inputs are not shown.
TALK-OFF PROBLEMS.
The response time and deresponse time
of the decoder circuit is set by R4, R5, and C6.
The purpose of this integrator is to pre ent
bouncing on and off any time a short duration
of low frequency audio is detected. In com-
mercial operation, the circuit would normally
be set up to respond in 250 mSec. Howe er,
this short response time requires that the
transcei ers ha e special audio filters which
pre ent any oice audio from e er being
transmitted in the subaudible tone range.
Because amateur radio transcei ers rarely
ha e such filters, many are capable of trans-
mitting oice signals with audio components
easily getting down into the 100 Hz range of
the usual CTCSS tone frequencies used in re-
peaters. This can cause two problems: talk-
off, which is oice audio appearing out of
phase with the CTCSS tone and effecti ely
canceling it, and talk-on, which is oice audio
components appearing at the designated tone
frequency, e.g., 100 Hz. In the case of the lat-
ter, a man's oice could occasionally trigger
the CTCSS decoder in a repeater, each time
causing the repeater to key up for 3-5 seconds
until the tail drops.
Talk-on and talk-off can also be caused by
incorrect adjustment of the modulation or the
carrier frequency in the transcei er. If the au-
dio consistently bangs up against the limiter
because the mic gain is too high, the squared
off audio can cause low frequency compo-
nents which trigger the CTCSS decoder. The
answer to this problem is for the user to
properly adjust the mic gain and limiter in his
radio. Likewise, off frequency operation of
the transcei er causes distortion by ha ing
modulation sidebands extend o er the sharp
edge of the i-f filter in the recei er.
To minimize these problems for amateur
radio ser ice, we ha e chosen alues for the
integrator circuit which pro ide a slightly
longer response time, about 500 mSec, mak-
ing it much less likely a oice component
could be long enough to cause a response. Of
course, this may cause a noticeable delay in
pickup time when someone keys the repeater.
If you prefer to shorten the response
time, you can lower the alue either of C6 or
of R4 and R5, perhaps cutting them in half.
You can try the new alues for awhile and see
if the change is acceptable.
REPAIR.
The only special repair procedure is re-
placement of a damaged ic. Because it is a
surface mount de ice, con entional desolder-
ing techniques may not remo e enough solder
to allow remo al. If you know for sure that
the ic is dead, it is simpler and it protects the
pc board from damage if you use a fine pair of
cutters to cut each lead of the ic at the edge
of the package. Then, unsolder and remo e
one lead at a time. After that, it is relati ely
easy to use a acuum desoldering tool or Sol-
der Wick to remo e any excess solder prior to
installing a new ic. Refer to the assembly in-
structions for information on orientation of
the ic.
PARTS LIST.
Note: Factory built units use surface
mount caps and resistors on the rear of
the board.
Ref # Value (marking)
C1-C2 0.1 µf 805 smt
C3 2.2 uf electrolytic
C4 0.1 µf 805 smt
C5 2.2 uf electrolytic
C6 0.1 µf 805 smt
C7 2.2 uf electrolytic
C8-C9 33 pf NP0 850 smt
D1-D2 1N4148 diode
Q1 2N3904 NPN xstr
R1 4.7K 805 smt resistor
R2 20K trim pot.
R3 10K 805 smt resistor
R4 3.9 meg 805 smt resistor
R5-R6 2 meg 805 smt resistor
S1 7 pos. DIP switch
U1 MX465DW ic
U2 78L05 5V regulator ic
Y1 4.000 MHz crystal
Table 2. U1 Test Voltages
Pin# Function Test Voltage
1 V
DD
+5V
2 Oscillator 7V p-p @ 4 MHz
3 Oscillator 5V p-p @ 4 MHz
4 Load/Latch +5V
11 V
SS
0V
12 Comparator Ref +3.2V
13 RX Decode ** +5V no tone, 0V tone
14 Comparator In ** +4.2V tone, 0 no tone
15 RX Detect ** +5V tone, 0V no tone
16 Tone Out ‡ 2.2V p-p tone
19 RX Out +2.5V
20 TX Out +2.5V
21 Bias Bypass +2.5V
22 TX In +2.3V
23,24 RX AF In +2.5V
** Receive Mode Only
‡ Transmit Mode Only

©2009 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. evised:
10/28/10
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