HAMTRONICS COR-3 User manual

©1990 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a register
ed trademark. anual revised:
10/2/07
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Page
1
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FUNCTIONAL DESCRIPTION.
The COR-3 module is designed for
operation with Hamtronics fm exciters
and receivers and CWID oard to pro-
vide repeater operation. The unit
may also e used with other makes of
transmitters and receivers if the re-
quired interface signals are availa le.
The COR-3 module features a
courtesy eep tone, which helps to
prevent talk over y encouraging us-
ers to wait a short time efore picking
up the repeater. After the waiting pe-
riod, a eep sounds on the repeater
and the time-out timer is reset. Wait-
ing this short period allows any new
party to reak in and identify himself.
The unit comprises four main circuits.
1. An electronic carrier-operated
relay provides operating power to the
exciter in the transmitter enclosure
whenever the receiver squelch is open.
U1-B senses the presence of a COS
signal from the receiver and keys the
first timer, U1-A, which provides the
courtesy wait period. That trips timer
U1-D, which provides the silent re-
peater tail. That timer, in turn, keys
Q1/Q2, which switches the B+ to the
exciter. If the receiver should e held
on for longer than the legal transmit
period, (e.g., 5 minutes), time-out
timer U1-C automatically shuts down
the transmitter until the receiver is re-
leased.
2. An audio oscillator and pulse
generator circuit provides the eep
signal. The output of timer U1-A trig-
gers one-shot multivi rator U2-C/D
when the waiting period elapses. The
one-shot keys square-wave oscillator
U2-B. The audio output is integrated
y an R/C network to create a sign-
wave tone, which is applied to the
mixer for output to the exciter audio
circuits.
3. Audio mixer stage U2-A mixes
three audio inputs from the receiver,
the CWID, and the eep generator to
provide the audio for the transmitter.
The receiver audio level is set at the
receiver to a predetermined level. Pots
on the COR-3 oard adjust the levels
of the CWID signal and the eep tone
to the desired levels relative to the re-
ceiver audio.
4. A speaker amplifier which pro-
vides adjusta le drive for a local
speaker separate from the repeater
audio, U3, avoids having to use "L"
pads, etc. and compromising local
audio for enefit of repeater. This
allows the receiver audio to e run at
a low level to avoid distortion.
Refer to catalog for complete
COR-3 module specifications.
CONSTRUCTION.
There is no special construction
sequence; ut following are some
notes regarding various parts.
a. Resistor odies are designated
as circles on the assem ly diagram for
those which are mounted vertically.
. Note the polarity of ic's, transis-
tors, diodes, and electrolytic capaci-
tors.
c. Trim pots may e marked with
significant figures and multipliers,
such as "105" for 1 megohm.
d. Terminal pins for E1-E15
should e cut from the metal carrier
strip, then snapped in place from top
of oard using care not to crush them.
Firm pressure with a pair of fine nose
pliers grasping one wall of the pin will
cause it to snap and lock into hole.
e. Use ic sockets for U1 and U2
ut not for U3, which must e sol-
dered to the oard for heatsinking.
f. Be careful not to interchange re-
sistors which have similar appearing
color ands, eg., 150K and 510K or 1
meg and 10 meg.
INSTALLATION.
The COR-3 module can e
mounted with standoffs in the four
corners of the oard. No special
shielding is required. Connections are
made to the terminal pins either y
soldering hookup wires into hollow top
of pin or wrapping around pin and
soldering. Following are descriptions
of required interface connections.
When used with Hamtronics exciter,
receiver, and CWID oards, required
interface levels are assured. When
used with other equipment, some care
must e taken to e sure compati le
interface connections are arranged.
Referring to the Repeater System dia-
gram, it can e seen that the ex-
citer/pa and the receiver are mounted
in rf tight oxes with feedthru capaci-
tors used at control and audio signal
entrances.
a. COS OUTPUT FROM
COS OUTPUT FROM COS OUTPUT FROM
COS OUTPUT FROM
RECEIVER.
RECEIVER.RECEIVER.
RECEIVER. This control signal at E7,
taken from the squelch stage in the
receiver must e a out +3 to +10 Vdc
when the squelch is open and near
ground when squelch is closed.
. AUDIO FROM RECEIVER.
. AUDIO FROM RECEIVER.. AUDIO FROM RECEIVER.
. AUDIO FROM RECEIVER. The
high level audio output from the ic in
the receiver, which normally feeds the
speaker, is connected to E6 on the
COR-3 oard instead. The COR-3
oard applies it to the audio mixer
stage for application to the exciter.
The receiver audio is also connected
through a (user supplied) 100K SPKR
VOL control to E14. A speaker am-
plifier on the COR-3 oard amplifies
the signal from the SPKR VOL control
to provide an isolated signal for a local
speaker on the repeater panel. The
nominal audio level at E6 should e
1.5V p-p at full 5 kHz deviation on the
receiver.
c.
..
. LOCAL SPEAKER
LOCAL SPEAKER LOCAL SPEAKER
LOCAL SPEAKER connected to
E15 on COR-3 oard should e an
8-ohm speaker. Up to 2W of audio
can e o tained from the COR-3
speaker amplifier. Note that the
speaker must return to ground.
d. B+ FOR COR
B+ FOR CORB+ FOR COR
B+ FOR COR-
--
-3 BOARD
3 BOARD3 BOARD
3 BOARD should
e +13.6Vdc connected to E3.
Ground should e tied to E10 unless
a good ground is picked up through
the mounting hardware from the
chassis. Current drain depends on
speaker level and amount of current
supplied to exciter keyed B+ line, ut
normally should e a out 600-700
mA.
e. KE
KEKE
KEYED B+ TO EXCITER
YED B+ TO EXCITERYED B+ TO EXCITER
YED B+ TO EXCITER at E1
is +13.4Vdc (slight drop in Q2) at up
to 600 mA. Because the pa is class C,
it is unnecessary to switch the B+ to
the pa.
f. REPEATER AUDIO
REPEATER AUDIOREPEATER AUDIO
REPEATER AUDIO from E5 is
connected to the microphone input of
the exciter. A 500 ohm dynamic mi-
crophone can also e connected to the
same exciter input. Resistor R47 pre-
vents the microphone from eing
loaded down.
g. LOCAL KEY
LOCAL KEYLOCAL KEY
LOCAL KEY input E12 may e
grounded y the local microphone PTT
switch to key the transmitter locally.
h. Connections to CWID are as
shown on the Repeater System dia-
gram. ID TRIP normally is high and
goes low when the receiver squelch
closes and the eep timer elapses to
provide a pulse to trip the id. The ID
KEY signal normally is low and goes
high to key the COR circuit while the
CWID runs. The CWID audio output
should e tied to E4, the input to the
audio mixer on the COR-3 oard. The
CWID input level at E4 normally is
a out 4kV p-p.
i. Outputs at E2, E8, and E11
drive front panel led's to indicate re-
peater status. Led's are not supplied
with this kit, ut they are supplied in
the hardware package if you ought a
complete Hamtronics Repeater Kit.
HAMTRONICS® COR-3 MODULE: INSTRUCTION MANUAL

©1990 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a register
ed trademark. anual revised:
10/2/07
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Page
2
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ADJUSTMENTS.
a. Adjust R3 for desired eep de-
lay time. Delay is adjusta le up to
a out 5 seconds.
. Adjust R8 for desired repeat tail
time. Delay is adjusta le up to a out
15 seconds.
c. Adjust R36 for desired time-out
period, up to five minutes. (Note that
the timer depends on an R-C time
constant with large values of R and C.
The time out timer may require a
reak-in period of a week or two e-
fore the time out period is sta le. Un-
til the capacitor is fully formed y
having a charge applied for an ex-
tended period, the maximum time pe-
riod for relia le time-out operation
may e limited. If set to too long a
period, the timer may not time-out.)
d. Set up repeater audio level as
follows. If a microphone will e used,
set exciter controls for normal micro-
phone operation as stated in exciter
instruction manual. Then, adjust
volume control on receiver for desired
repeat modulation (exciter deviation to
match received signal deviation).
If there is no microphone in the
system, set the receiver volume con-
trol for a out 1.5V p-p audio into the
COR-3 module (a fairly low volume
control setting on the receiver to avoid
distortion); and then set the exciter
mic gain control for proper deviation.
If an autopatch is used, follow the
audio setup instructions supplied
with the autopatch module.
It normally is not desira le to use
the limiter in the exciter; since it may
add a little distortion on peaks. The
receiver crystal filter limits the
amount of deviation of the received
signal, there y automatically limiting
the transmit signal. However, when
an autopatch is used, the limiter in
the transmitter is used in order to
prevent overdeviation on loud audio
peaks from the telephone.
e. Adjust LOCAL VOLUME control
to set speaker volume.
f. CWID modulation level is ad-
justed with R42. Normally, the ID level
is set lower than voice level, eg., 2 to 3
kHz deviation.
g. Set courtesy eep level with
R34. This normally is set for a out 3
kHz deviation.
TO DISABLE COURTESY
BEEP.
To disa le courtesy eep tem-
porarily, merely turn down eep level
pot R34. Set R8 to full CCW, and set
tail time with R3 so eep occurs at
carrier drop. To permanently disa le
eep, remove C9 or C11.
NOTE ABOUT CWID
INTERFACE.
In the normal configuration, if the
COR-3 module is used with the CWID
module, the id is tripped at the same
time the courtesy eep occurs; so
there may e an annoying overlap of
the eep with the first it of the id
message. To prevent this pro lem,
there are two easy cures.
The first is to leave the first row on
the CWID oard lank to force a
pause efore the id message.
The second method, preferred if
you already programmed your id
oard or if you need to use the entire
capacity of the id matrix, is to change
the trigger point from which the ID
TRIP line gets its input to a later timer
stage. To do this, disconnect C4 from
U1-A pin 4, and reconnect it to U1-A
pin 10 (solder to lead of R13 closest to
middle of oard). The disadvantage of
the second method is that the id now
trips as a function of the tail timer,
and if you don't drop the tail, the id
doesn't trip every ten minutes as re-
quired. Therefore, method #1 is pre-
ferred.
THEORY OF OPERATION.
The 3301 quad op-amp is a Norton
type for single supply operation. The
voltage applied through various resis-
tor values to the (+) and (-) inputs
cause the output to go high or low,
depending on which input has more
current flowing. The amount of cur-
rent depends on the voltage and re-
sistance. In some cases, positive
feed ack resistors are used for
Schmitt trigger action (snap action).
The receiver COS signal is applied
to threshold detector U1-B. Its
threshold is set y the ratio of R1 to
R2. When the squelch opens, the
COS signal exceeds the 2V threshold,
and U1-B goes high. This turns on
U1-A, which in turn activates U1-D.
The positive signal applied to U1-D
causes the output to go high and turn
on Q1 and Q2, which applies B+ to
the exciter.
The ratio of R5 to R7 sets the turn-
on threshold of U1-A at +3V. When
the receiver is open, +12V is applied
to R5. When the squelch closes, C2
discharges slowly through R3-R4.
When the voltage decays to +3V, U1-A
turns off. The quick-attack, slow-
release action of CR1/C3/R3/R4 pro-
vides a period of adjusta le length
etween the time the receiver squelch
drops and the courtesy eep occurs.
When the squelch closes and the out-
put of U1-A goes low, an ID TRIP sig-
nal pulse is generated y C4-R20 for
the CWID module. This is a "polite"
ID trip; it waits until you stop talking
to ID.
Timer U1-D operates in the same
manner as U1-A; however, it provides
the time delay after the courtesy eep,
the normal silent carrier tail time. R8
adjusts the delay etween the cour-
tesy eep and the carrier dropping.
When U1-A drops, C9/R23 applies
a negative-going pulse to one-shot
multivi rator U2-C/D, which then
produces a short square wave pulse to
trigger the courtesy eep. This pulse
activates oscillator U2-B for a short
period of time. The audio square wave
output of the oscillator is integrated
y R33/C12 to produce a sine-wave
tone, which is applied to one input of
audio mixer U2-A.
U1-C provides a time-out timer to
prevent the repeater from hanging up
if the receiver stays open. The timer
length is set y the charging of C10
through R36-R37. It is reset quickly
through CR4 each time the receive
squelch closes and U1-A drops. When
the voltage of C10 reaches the 4V
threshold, the output of U1-C snaps
to +12V, which is applied through
R15 to the (-) input of U1-D. Since
the value of R15 is lower than R10,
U1-C can positively override the key-
ing of the exciter.
A third input to U1-D from E12 via
R16 has veto power over oth of the
other inputs. If the local keyline is
grounded, U1-D turns on, regardless
of other signals it receives. Likewise,
when the CWID is running, a TTL
high is applied from E13 via CR3 and
R12 to hold U1-D on.
Speaker amplifier U3 receives au-
dio from the SPKR VOL control to
drive the local speaker. Voltage di-
vider R48-R49 reduces the gain of U3
to a practical level, since it is driven
from a high level input.
U2-A is iased as a class A ampli-
fier. The three inputs via R35, R43,
and R44 mix the courtesy eep tone
and the CWID audio in with the re-
ceiver audio to drive the microphone
input of the exciter. R47 works in
conjunction with the 2K input resis-
tance of the exciter to reduce the au-
dio to the desired 30 mV p-p level and
provide isolation from the local micro-
phone (if used). If you are not using a
Hamtronics® exciter, you may wish to
change or remove R47 to o tain
proper driving level for your exciter.

©1990 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a register
ed trademark. anual revised:
10/2/07
-
Page
3
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TROUBLESHOOTING.
Having read the Theory of Opera-
tion, you have a good understanding
of how the circuits work. The est
way to trou leshoot is to use the fol-
lowing sample voltages to check the
operation of each circuit.
Notes:
* This value is used in place of value
on schematic due to parts shortage.
** Due to parts shortage, several 1
meg resistors are replaced with two
510K resistors in series (tack solder at
joint).
PARTS LIST.
Note: ➊indicates surface mount part in-
stalled under board
Ref # Value (marking)
C1 .001 uf (102, 1nM, or 1nK)
C2-C3 4.7 uf electrolytic
C4-C6 .001 uf (102, 1nM, or 1nK)
C7 47 uf electrolytic
C8 0.15 uf mylar (red)
C9 100pf (101) or 120pf (121)
C10 470 uf electrolytic
C11 .01uf (103)
C12 220 pf (221)
C13-C14 .001 uf (102, 1nM, or 1nK)
C15 .01 uf (103)
C16 0.47 uf electrolytic
C17 .001 uf (102, 1nM, or 1nK)
C18 4.7 uf electrolytic
C19 47 uf electrolytic
CR1-CR4 1N4148
E1-E15 Terminal pins
Q1 2N3904 or 2N4124
Q2 D45C1 or TIP-30
R1 150K
R2 1 meg ** (2ea 510K series)
R3 1 meg pot
R4 6.8K *
R5 510K
R6 10 meg
R7 2 meg
R8 1 meg pot
R9 6.8K *
R10 510K
R11 10 meg
R12 100K
R13 6.8K *
R14 2 meg
R15 330K
R16 100 ohms
R17 330 ohms, 1/2W
R18 680 ohms
R19 470 ohms
R20 not used
R21-R23 ➊1 meg
R24 2 meg
R25 27K
R26 ➊1 meg
R27 150K
R28 2 meg
R29 ➊1 meg
R30-R31 10 meg
R32 27K
R33 1 meg ** (2ea 510K series)
R34 1 meg pot
R35 2 meg
R36 1 meg pot
R37 150K
R38 3.9 meg
R39 22 meg
R40 10 meg
R41 680 ohms
R42 1 meg pot
R43 2 meg
R44 1 meg ** (2ea 510K series)
R45 ➊1 meg
R46 2 meg
R47 68K
R48 ➊1 meg
R49 330K
U1-U2 LM3301 or LM2900
U3 LM-380
TYPICAL DC VOLTAGES (WITH 13.6V POWER SUPPLY):
CONDITION U1-1 U1-5 U1-2 U1-4
Rcvr Open 0.6 12.6 0.6 12.6
Rcvr Closed 0 0.1 0.1 0
C2&C3 U1-12
Rcvr Open 12 0.6
Rcvr Closed 12>0 0
U1-10 Q1-C C2-B Q2-C
Xmtr On 12.6 0.3 12.8 13.4
Xmtr Off 0.1 13.0 13.0 0.1
C10 U1-13 U1-9 U1-11
Normal 0.4V 0.1 0.1 0.03
Timed Out Charged 0.6 12.6 0.6 to 4V
U3-1 U3-6 U3-8 U2-2,3 U2-4
7 .03 6 0.6 7
TYPICAL AC VOLTAGES (FULL 5 KHZ DEVIATION):
TEST POINT P-P VOLTAGE
E4 CWID In 4V
E6 Rcvr AF 1.5V
E5 Mixer Out 30mV (2K load)
U2-4 1.5V
U2-5 12V square wave
Top of R34 4V sine wave
U3-6 Up to 0.4 V
U3-8 up to 8V

©1999 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. anual revised:
10/2/07
-
Page
4
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©1999 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. anual revised:
10/2/07
-
Page
5
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