©1990 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a register
ed trademark. anual revised:
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.
