Realistic TRC-449 User manual

®
'. " J?<EALIShc
-
ervlce
TRC-449
CB TRANSCEIVER
Catalog Number: 21-1562
~ CUSTOM MANUFACTURED FOR RADIO SHACK MA DIVISION OF TANDY CORPORATION

~---- TABLE OF CONTENTS -------,
1. SPECI FICATIONS ................................ 3'" 5
2. DISASSEMBLY INSTRUCTIONS ....................... 6
3. BLOCK DIAGRAM •................................ 7
4. ALIGNMENT INSTRUCTIONS .................... 8'" 16
5. TROUBLESHOOTING HINTS ..................... 17'" 18
6. PLL CI RCUIT TROUBLESHOOTING HINTS ............ 19
7. IC. TRANSISTOR & DIODE LEAD IDENTIFiCATIONS .... 20
8. IC & COMPOUND PARTS INTERNAL DIAGRAMS ....... 21
9. CHANNEL SWITCH P.C. BOARD (FLEXIBLE) ........... 22
10. NOISE
BLANKER P.C. BOARD ....................... 22
11. SPEAKER
JACK P.C. BOARD (TOP & BOTTOM) ......... 22
12.
MAIN P.C. BOARD (TOP VIEW). ...................... 23
13.
MAIN P.C. BOARD (BOTTOM ViEW). ................. 24
14. ADDITIONAL PARTS ON THE BOTTOM .............. 25
15.
WIRING DIAGRAM ................................. 26
16.
WIRING DIAGRAM ................................. 27
17. WIRING DIAGRAM ................................. 28
18.
ELECTRICAL PARTS LiST ..................... 29"" 42
19.
MECHANICAL PARTS LIST .................... 43'" 45
20. SCHEMATIC
DIAGRAM .............. (SEPARATE SHEET)
21. EXPLODED
ViEW ................... (SEPARATE SHEET)
-2-

GENERAL:
Channels
Frequency
Range
Frequency Control
Frequency Accuracy
Operating Temperature
Range
Power Requirements
Antenna
Microphone
Speaker
Size
Weight
Accessories
1. SPECIFICATIONS
: 40 Channels for AM, Upper Side Band and Lower Side Band,
utilizing Digital Circuitry
: 26.965 MHz to 27.405 MHz
: Digital
(Phase Lock Loop) Synthesizer
: ±100
Hz
: -20°C to +50°C
: 13.8V
DC (12-16 volts DC, negative or positive ground)
:
52 ohm (Coaxial connector)
: 600 ohm Dynamic Type
: 8 ohm, 3 Watt
:
2-3/8" x 7-7/8" x 10-1/2" (HWD) (6 x 20 x 26.6 cm [HWD])
: 6 Ibs. (approx.) (2.65 kg)
: DC Cord with in-line Fuse, Microphone and Microphone Hanger
and Mounting Brackets
MEASUREMENT CONDITION:
Power Source
Antenna Impedance
Test Temperature
AM Modulation Frequency
: 13.8V
DC
: 50 ohm
: 25°C
: 1 kHz
SSB Modulation Frequency, Transmit : Two tone: 500 Hz and 2400 Hz
Single tone: 1 kHz
Mean Signal I nput Level
Reference Audio
Output Power
: 1000
/lV
:0.5W
Reference AM Modulation Percentage : 1 kHz 30%
Audio Frequency, SSB Receive
Audio
Output Load
Measuring Channel
: 1 kHz
: 8 ohms resistive
:
19
-3-

RECEIVER: (ANL & Noise Blanker Switch OFF)
Max. Sensitivity : AM
Sensitivity
for 10 dB SIN
AGC Figure of Merjt 50 mV for
10 dB Change in Audio Output
Overload AGC Characteristics from
10 mV to 100 mV
Overall ,Audio Fidelity at 6 dB Down
Upper Frequency
Lower Frequency
---
Cross Modulation, RS Standard
Adjacent Channel Selectivity
(10kHz)
Maximum Audio Output Power
'f '
Audio Output Power at 10% THD
THD at 500 mW Audio Output
AM: 1 m.V Input, 30% modulation
80% modulation
SSB: 1 mV Input 1 kHz Single',tone
RF Gain Control
Range at Max.
Sensitivity Level
S1N -Riltio at Input 1 mV
Squelch Sensitivity at Threshold
S Meter Sensitivity at IIS-9"
(No Modulation AM)
, Image Rejection Ratio. fo+(2x7.8 MHz)
1/2 IF Rejection Ratio. fo+7.8 MHz/2
IF Rejection Ratio. 7.8 MHz
Oscillator
Dropout Voltage
Clarifier
Range
Spu rious Rejection Ratio In band
Out of Band
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
:AM
, SSB
:AM
SSB
:AM
SSB
:AM
:AM
: SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
:AM
SSB
· -4 -
UNIT
p.V
p.V
p.V
p.V
dB
dB
dB
dB
Hz
Hz
Hz
Hz
dB
dB
dB
W
W
W
W
%
%
%
dB
dB
dB
dB
p.V
p.V
p.V
jJ.V
dB
dB
dB
dB
dB
dB
V
V
kHz
kHz
dB
dB
dB
dB
NOMINAL
0.5
0.25
0.5
0.25
90
90
±3
±3
2100
3500
450
450
60
65
65
4
4
3
3
3
5
3
40
40
50
50
0.5
0.25
100
100
80
80
90
90
85
85
9
9
±1.25
±1.25
65
65
60
60
1
0.5
1,
0.5
80
80
±5
±5
LIMIT
1750 '" 2500
2500 '"
5000
300'" 650
300'" 650
50
54
54
3
3
2.5
2.5
6
12
6
30'" 50
30'" 50
40
40
1
0.5
25'" 400
25'" 400
70
70
80
80
75
75
11
11
±0.6 -- ±2.5
±0.6'" ±2.5
56
56
50
50

UNITS
NOMINAL
LIMIT
Battery Drain at No Signal
:AM
mA 550 1000
5SB
mA
550 1000
Battery Drain at Maximum Output Power
:AM
mA 1500 2000
SSB
mA 1500 2000
PUBLIC ADDRESS:
Microphone Sensitivity for
3W Output Power at 1 kHz mV 1 3
Maximum Output Power W 4 3
TRANS M ITTER:
Frequency Tolerance at 25°C (5 Minutes
after switch on)
:AM % ±0.0005 ±0.003
SSB
% ±0.0005 ±0.003
Carrier Power at No Modulation
:AM
W 3.8 4.0
PEP Power, Two Tone : SSB W PEP 12
12.0
Modulation Distortion at 1 kHz, 80% Modulation :AM % 3
10
Spurious Harmonic Emission
:AM
dB -65 -60
SSB dB -65 -60
Carrier Suppression :
5SB
dB -55 -40
Unwanted Sideband Suppression at 25 kHz :
SSB
dB -55 -40
Modulation Frequency Response
(1 kHz, 0 dB reference)
Lower
at 450 Hz, EIA
:AM
dB
-6
-10
SSB
dB
-6
-14
Upper at 2.5 kHz, EIA
:AM
dB -6 -10
5SB dB
-6
-10
Carrier Power Uniformity,
Ch to Ch at No Modulation :AM
W 0.3 0.4
Mic Input Level Uniformity, Ch to Ch for 4 watts
Output .25 kHz Single tone - SSB
dB 2 3
Mic I nput Level Uniformity, LSB to USB for
4 watts Output, 1.5 kHz Single Tone dB 3
Microphone Sensitivity
AM:
For 50% Modulation
:AM mV 1.0 2.0
SSB:
For 4 watts PEP : SSB
mV
1.0 2.0
AMC Range
AM:
50 -- 100% Modulation
:AM
dB
46 40
SSB:
10 -- 13.2 watts PEP 5SB dB
46
40
Battery Drain at No Modulation
:AM
mA 2200 2600
SSB mA
1000 1500
Battery Drain
AM:
80% Modulation :AM
mA 2600 3000
SSB: 10 watts PEP, Two tone
SSB
mA
2000 2700
Note; Nominal
Specs represent the design specs; all units should be able to approximate these, some will
exceed and some may drop slightly below these specs.
Limit Specs represent the absolute worst condition which still might be considered acceptable, in
no
case should a unit perform to less than within any Limit Spec.
- " 5-

Figure 1
2. DISASSEMBLY INSTRUCTIONS
Figure 2
Figure 3
-6-
1. To remove Top & Bottom Cover: (Figure 1)
Remove 4 screws from each side and a
screw
from top. SI ide the top toward the
rear
of the chassis and remove.
2.
To remove Front Panel: (Figure 2)
Remove 2 screws
from each side.
Figure 4

--J
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3. BLOCK DIAGRAM
---------- - --- ~9 --------------------------·
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____ _ __ +_1- _____ I J I
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RX
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DC
+ 13 .8V
CL
J;
CL
(j)
I-
z

4. ALIGNMENT INSTRUCTIONS
CHASSIS LAYOUT-ALIGNMENT POINTS
L30
L27
@J
L32 (§
0 0
0VR'6
@J
VRI5
VR8 L 3
LI
en
VRI2 0
~~
(ill]
@J
@J@J
L4
V RI
~@
VR3 VR2
L37
LB
;
~
CTI
0 L 5
(§)
@)
~
VR5
l39
L7
@}
~~
VR4
L 24
vR 9
!e§) 6)1
§J
CT6 0
Ll 7 0
~
VR6
CT5
[ill)
~
0 VR7
[ill)
Ll6
CT4
0 CT2
00
CT3
D
-8-

ALIGNMENT OF PLL AND CARRIER OSCILLATOR
1. Test equipment required:
a. Oscilloscope (DC -50 MHz)
b. Frequency counter (0 -30 MHz)
c. DC Power Supply (13.8V 100 mA)
d. DC Voltmeter (1 OV Maximum 100Kohm/V)
e. 50 ohm Load
2.
Alignment procedure: (See page 8)
Connect Test Equipment
as shown below.
STEP PRESET TO CONNECTIONS
ADJUSTMENT
REMARKS
1 RX, AM, CH19 TP6 L24 Adjust
for max. output.
Clarifier: in center position
2 RX, AM,
CH 1 TP7 L17 Adjust
for 2 V reading on Voltmeter.
Clarifier: in center position
3
Same as Step 1 TP8 L16 Adjust
for max. output.
4 Same as Step 1 TP8 CT6
Adjust to obtain 34.985 MHz ±20 Hz
on frequency Counter.
5 RX, USB, CH19 TP8 CT4 Adjust
to obtain 34.9875 MHz ±20 Hz
Clarifier, in center position on frequency Counter.
6 RX, LSB, CH19 TP8 CT5 Adjust
to obtain 34.9825 MHz ±20 Hz
Clarifier: in center position on frequency Counter.
7 TX, LSB, CH19 TP8
VR9
Adjust to obtain 34.9825 MHz ±20 Hz
on frequency Counter.
S Same as Step 7 TP9 CT3 Adjust
to obtain 7.7975 MHz ±5 Hz
on frequency Counter.
9
TX,USB,CH19 TP9 CT2 Adjust
to obtain 7.8025 MHz ±5 Hz
on frequency Counter.
PLL AND CARRIER OSCILLATOR TEST EQUIPMENT SETUP
EJE]
DC Power Supply
13.8V
-9-
Frequency Counter
o Oscilloscope
DC
Voltmeter

PLL (Phase Lock Loop) CIRCUIT DESCRIPTION
The PLL (Phase Lock Loop) circuit used in the
TRC-457 consists
of 6 major components; Voltage
Controlled Oscillator (VCO), 1/N Divider, Refer-
Fvco
34.7625 MHz
I
35.2075 MHz
IC 5
V.C.O.
I[]
- - -- -- 'oom'
•. • _--- -- 0
-- -- -- - - 200mv
''' 1 /
f '''L ~
1.9VC"lC~
FET 4
Mixer 0.91 MHz
I
1.35 MHz
33.
8575 MHz
I
33.8525 MHz
ence Oscillator, 111024 Divider, Phase Detector
and Low Pass Filter.
AMP
--- •• -- -. - -- -- - l lV
mTI
---- - --------1."
--- -- - ---- -- --- -0"'
le7
TR 31
Buffer Amp.
IAI1I1 "' 1
1__U ___ U..}o .5v
-- - -· - ----- --- ·· ov
70 . 91 ~ 1.35 MHz
r-------------------------,
X'tal3 a TR 34
OSC
11 . 2858MHzT 1....-----'
TR 35
Filter
TR
40
I Filter PHASE
Oetector
10 kHz
1/1024 I
Divider
r--_-.lf10 kHz •
I 10.24 MHz I
Programmable Divider REF.
OSC I
X'tal4 r---
Cl
TR 38
OSC
Tripier
l /N (91-135) l
f--- i
~ L-----------e------- _____ J
11.2842 MHz T
X'tal6 r---
C
11.2850 MHz T TR 39
OSC
I[J
Channel Selector
X'tal5
The VCO is an oscillator which controls oscilla-
·
tion frequency in accordance with input voltage
changes. The VCO output is mixed with a signal in
the transmitter
or receiver circuitry. A portion of
the VCO frequency is fed to FET4 and mixed with
a 33.8525 -33.8575 MHz frequency from X3, X4
or X6 and then goes through TR30 Amplifier and
TR31 Buffer Amp and then added to the 1/N
Divider. This is applied to one input of the Phase
Detector. "N" for the 1/N Divider is determined
by the Channel Selector Switch
(by BCD) and
varies from 91 to 135.
On the other hand, a 10.24 MHz frequency
from
the Reference Oscillator is divided to 10kHz by
1/1024 Divider and applied to another input of the
Phase Detector. The Phase Detector detects the
difference
of these two input signals and produces
a voltage which controls the VCO frequency. The
Low Pass Filter integrates the outpuf voltage of
the Phase Detector which controls the VCO
frequency
and the 1/N Divider produces a 10kHz
frequency.
Thus the
Phase Detector receives two input signals
(both 10 kHz).
It compares the phase difference of
the two, generating an error voltage, which acts on
the VCO
to bring the two frequencies exactly in-
phase. When this condition occurs, the PLL circuit
is "Iocked".
Switch 10.
24 MHz
WAVE FORM O,F le7
IC7
Pin No.
Wave
Form
IC7
?inNo.
WiNe
Form
H - UN L OCKED
L = LOCKED
where
H = 3.5 - 6V
L = 0 - 1. 0V
a
2&3
5&6 7 & 12
\0
1illl
5V
NJ 5V lli10
5V m5V
\ - T\ - -,.( 2V _
__V _V_ 15V
-- - - - -0------ -0 -- - --0 - -- - 0 -------0
Note: Pin No. 13 through 18, 20 & 21 are as in frequency
chart.
Pin No. 19, 22 & 23 are fixed to Low level.
By varying the constant N, the output frequency
from the VCO can be locked and varied one
10kHz step at a time. The constant N is controlled
by the Channel Selector Switch. A frequency shift
of 2.5 kHz (required for AM RX, USB and AM TX
and LSB RX/TX) is obtained by switching to X3,
X4 or X6 as shown in Frequency Chart.
For a more detailed description of how this circuit
functions, refer to Abbreviated Block Diagram as
well as the full Block Diagram and Schematic.
-10 -

1) PLL LOCAL OSCILLATOR
FL, the frequency of the VCO, is controlled by
the
PLL synthesizer system as follows. The output
frequency of the VCO (I C5) is applied to one of
the inputs of the In-loop Mixer FET4 and mixed
with the off-set frequency which is generated by
the Off-set Oscillator
TR34 or TR38 and multi-
plied by three by Tripier TR40.
The resultant difference frequencies
are produced
at the
output of FET4 as follows:
F1 Output frequency of FET4
Fo Off-set frequency, approximately, 11.2858
MHz on AM or USB mode and 11.2842
MHz on
LSB mode.
3 x
Fo: 33.8575 MHz on AM or USB mode.
33.8525 MHz on
LSB mode.
F1 falls into the range of 910kHz to 1350 kHz in
increments
of 10 kHz.
F1
is applied to the Programmable Frequency
Divider in the
PLL Ie, IC7, after being amplified
by TR30 and TR31, and then is divided by the
programmed-divide-ratio, N, by the Programmable
Divider.
The resultant frequency
is applied to the Phase
Detector in IC7 and is compared (phase-detected)
with the reference frequency of 10 kHz applied to
another input of the Phase Detector.
The
Phase Detector generates the control voltages
for VCO to minimize the difference between F1
divided by N and the reference frequency.
Thus, under locked
condition of the loop, the local
frequency
FL is locked stable and is calculated by
the following formula:
FL = N x 10 kHz +3 x Fo
2) CHANNEL SELECTION PROGRAM
The divide ratio, N,
of the Programmable Frequen-
cy Divider
is determined by supplied voltages to
the program input terminals, Pin No. 13 through
Pin No. 22
of the I C7.
The program input voltages for Pin No. 19, No. 22
and No. 23 are fixed to "Iow level", and the
voltages
for Pin No. 13 through No. 18, No. 20
and No.
21 are supplied from the channel selector
switch S408.
The
function of the program input terminals is as
follows:
Pin No. : 13 14 15 16 17 18 19 20 21 22
Function :
1A
1B
1C
10 2A
2B 2C 20 3A 3B
Significant 1 2 4 8 10 20
40
80
100200
number
* Program
Input "h igh level" 19 and 20 are
Kept "Iow" (off).
The divide ratio N of the Programmable divider is
provided by the sum of the significant numbers
which
are effective by supplying "high level"
input. For example, when the channel switch
is
set to Channel No.1, the input of 1A, 2A and 2D
is in "high level" and the others are in "Iow level".
Therefore, the divide ratio N
is determined as
follows:
N =1 + 10 +
80 = 91
In the same manner, the divide ratio N for Channel
No. 1 through No.
40 is determined as shown in
Frequency Chart.
3)
TRANSMITTING FREQUENCY CALCULA-
TION
For an example, when the unit is operated on
Channel 19, the transmitting frequency
is calculat-
ed as shown in the following table for each mode.
AM mode LSB mode USB mode
N 113 113 113
3 x
Fo (MHz) 33.8575 33.8525 33.8575
N x
10 kHz (MHz) 1.13 1.13 1.13
FL (MHz) 34.9875 34.9825 34.9875
FIF (MHz) 7.8025 7.7975 7.8025-
Ft (MHz) 27.185 27.185 27.185
-
11 -

FREQUENCY CHART
ANTENNA
1/N INPUT IC7 VOLTAGE LOCAL
OSC
CH
OUTPUT N OUTPUT FREQUENCY
FREQUENCY FREQUENCY
1A 1B 1C
10
2A
2B 20
3A
AM.RX USB&AM.TX LSB
1 26.965
91 910 1 0 0 0 1 0 1 0 34.765 34.7675 34.7625
2 26.975 92 920 0 1 0 0 1 0 1 0 34.775 34.7775 34.7725
3 26.985 93 930 1 1 0 0 1 0 1 0 34.785 34.7875 34.7825
4 27.005 95 950 1 0 1 0 1 0 1 0 34.805 34.8075 34.8025
5 27.015 96 960 0 1 1 0 1 0 1 0 34.815 34.8175 34.8125
6 27.025 97 970 1 1 1 0 1 0 1 0 34.825 34.8275 34.8225
7 27.035 98 980 0 0 0 1 1 0 1 0 34.835 34.8375 34.8325
8 27.055 100 1000 0 0 0 0 0 0 0 1 34.855 34.8575 34.8525
9 27.065
101
1010 1 0 0 0 0 0 0 1 34.865 34.8675 34;8625
10 27.075 102 1020 0 1 0 0 0 0 0 1 34.875 34.8775 34.8725
11 27.085 103 1030 1 1 0 0 0 0 0 1 34.885 34.8875 34.8825
12 27.105 105 1050 1 0 1 0 0 0 0 1 34.905 34.9075 34.9025
13 27.115 106 1060 0 1 1 0 0 0 0 1 34.915 34.9175 34.9125
14 27.125 107 1070 1 1 1 0 0 0 0 1 34.925 34.9275 34.9225
15 27.135 108 1080 0 0 0 1 0 0 0 1 34.935 34.9375 34.9325
16 27.155 110 1100 0 0 0 0 1 0 0 1 34.955
34.~575
34.9525
17 27.165
111 1110 1 0 0 0 1 0 0 1 34.965 34.9675 34.9625
18 27.175 112 1120 0 1 0 0 1 0 0 1 34.975 34.9775 45.9725
19 27.185 113 1130 1 1 0 0 1 0 0 1 34.985 34.9875 34.9825
20 27.205 115 1150 1 0
1·
0 1 0 0 1 35.005 35.0075 35.0025
21
27.215 116 1160 0 1 1 0 1 0 0 1 35.015 35.0175 35.0125
22 27.225 117 1170 1 1 1 0 1 0 0 1 35.025 35.0275 35.0225
23 27.255 120 1200 0 0 0 0 0 1 0 1 35.055 35.0575 35.0525
24 27.235 118 1180 0 0 0 1 1 0 0 1 35.035 35.0375 35.0325
25 27.245 119 1190 1 0 0 1 1 0 0 1 35.045 35.0475 35.0425
26 27.265
121 1210 1 0 0 0 0 1 0 1 35.065 35.0675 35.0625
27 27.275 122 1220 0 1 0 0 0 1 0 1 35.075 35.0775 35.0725
28 27.285 123 1230 1 1 0 0 0 1 0 1 35.085 35.0875 35.0825
29 27.295 124 1240 0 0 1 0 0 1 0 1 35.095 35.0975 35.0925
30 27.305 125 1250 1 0 1 0 0 1 0 1 35.105 35.1075 35.1025
31
27.315 126 1260 0 1 1 0 0 1 0 1 35.115 35.1175 35.1125
32 27.325 127 1270 1 1 1 0 0 1 0 1 35.125 35.1275 35.1225
33 27.335 128 1280 0 0 0 1 0 1 0 1 35.135 35.1375 35.1325
34 27.345 129 1290 1 0 0 1 0 1 0 1 35.145 35.1475 35.1425
35
27 .355 130 1300 0 0 0 0 1 1 0 1 35.155 35.1575 35.1525
36 27.365
131 1310 1 0 0 0 1 1 0 1 35.165 35.1675 35.1625
37 27.375 132 1320 · 0 1 0 0 1 1 0 1 35.175 35.1775 35.1725
38 27.385 133 1330 1 1 0 0 1 1 0 1 35.185 35.1875 35.1825
39 27.395 134 1340 0 0 1 0 1 1 0 1 35.195 35.1975 35.1925
40 27.405 135 1350 1 0 1 0 1 1 0 1 35.205 35.2075 35.2025
o :::: Low level (0 -1.0 volt)
1 = High level (3.5 - 6 volts)
-
12-

1. AUDIO LIMITER AND AUTOMATIC MODU-
LATION CONTROL
The modulation control for th is model consists of
2 loops of AMC which detect a signal from the
output of the audio limiter (mic preamp) and from
the audio power amp and feed it back to limiter
diodes.
TR20
AF AMP
LIMITER
Low pass filter
r
TR26
AM.TX.
021
022
MIC AMP
R84
I--~~'-----o MIC
Vee
(MODULATION
SIGNAl)
TR18
LIMITER
(CLAMPING)
Vee
R104
TR23
AMC
SWITCHING
023
BIAS SWITCHING
~I
AF. PWR. AMP.
Fig. 1 Circuit Diagram of Audio Limiter and
Automatic Modulation Control
1-A. AUDIO LIMITER
The mic signal is applied to pin 2 of IC3. The signal
is picked up at Pin 6 and detected by D20
(negative
part of waveform). This current flows
into the base of TR19, effectively decreasing it's
C-E impedance; which increases the Vcc applied
to TR18's base. And TR-18's C-E impedance drops
as its base current increases. This provides a
variable voltage divider at the
input of I C3 (divid-
ing between R84 and
TR 18), thus making it
possible to attenuate and control the modulation
signal right at the
input to the mic gain stages.
t
w
>
W
...J
Mf-
U::J
-0..
f-
::J
o
MODULATION SIGNAL---.
Fig. 2 Audio Limiter Characteristics
1-8. AUTOMATIC MODULATION CONTROL
(AMC)
The
output level of IC3 is already controlled by
the audio limiter. However, to control maximum
modulation more precisely and stably, the AMC
circuit which feeds back the output amplifier(lC4)
into the limiter diode(D21, D22) is provided. The
output of IC3 is subjected to impedance matching
by the
AF AMP(TR20) through the low pass
filter( L10, L11) and TX(AM) switching(TR22).
The
output of IC4 is subjected to impedance
matching by the
output transformer(T1) and sup-
plied to the TX FINAL and DRIVER stage. This
modulation signal
is detected at the secondary of
T1 by the bias switching diode(D23) and makes
collector current
flow in TR23, AMC transistor. At
this time, a voltage drop is developed across the
resistor(R104) which
causes collector voltage to
decrease and forward bias current of both D21 and
D22
is reduced. In other words, the output voltage
of I C3 is cl ipped for both positive and negative.
However, the
cl ipped waveform as shown in Fig.
2-D
causes the band-width to increase, thus a low
pass fi Iter(L10, L11), which has the characteristics
as shown in Fig. 3, is used.
-tH-
~
- J
Detected
ZERO _
__ __ _ _ _ by 023
Fig.2A Modulation Wave at
Antenna Terminal Fig.
26 Output
at T-1
\ I \ I I c+Pin
g level
Fig. 2C Limiter Output with Fig. 2D Limiter Output with
small
input signal large input signal
Fig. 3 Low Pass Filter
Frequency
Response
ATT. Level (dB)
o
10
20
30
1 2.8
INPUT FREQUENCY
(KHZ)
2. AUTOMATIC LIMITER CIRCUIT(ALC)
(SSB mode)
Both AMC and ALC circuits function for AM and
SSB. For SSB we have an additional circuit as
described here.
CT7
ALC
FT1 TR6
Crystal Filter 7.8 MHz AMP
013
SWITCHING
R45
. ~----Mr---o Vee
To Antenna Transmitter Stage
Fig. 4 ALC circuit (abbreviated)
-13 -

The SSB signal is processed through FT1, amplified
by the 7.8 MHz amplifier(TR6)
and fed to the TX
stage. The peak-to-peak power output of the TX
stage is subjected to negative detection .by 046 an?
applied to the gate of FET5 ALC amplifier. At this
time,
if the gate becomes negative, drain voltage is
increased up to about Vcc level. This increased
voltage
is applied to the case of TR42 ALC
amplifier, and therefore, base current is incr~as~d
which also increases collector current; this in-
creases R45 voltage drop and decreases collector
voltage.
The
base bias of TR6 is supplied from the collector
of TR42 through the switching diode(013). With a
decrease in the collector voltage
of TR42, the base
bias current of TR6 js reduced and the operating
point is shifted, thus amplifier output level is
decreased as shown in Fig.5. This decrease will
limit the power output at the antenna terminal.
ALC ON con di tion
Ope rating Point
ALC 0 FF condition
Operating P
oint
Input Signal
Input Signal
Fig. 5 Operating Characteristics of TR-6
3. NOISE BLANKER CIRCUIT
3-A. NOISE AMPLIFIER CIRCUIT
The Noise Blanker circuit is tuned to 23 MHz.
Any noise that exists in the 27 MHz frequency
range
will also be present at 23 MHz. L1 is tuned
to 23 MHz, IC1 amplifies the 23 MHz band
of
frequencies and L2 provides further tuning. This
signal
is then amplified and detected (utilizing ~he
non-Iinear characteristic portion of the operating
curve)
by TR2, N.B. AMP. Also, the phase of the
signal .
is reversed in TR2 and fed to the base of
TR3 for further amplification. Base current flows
when a pulse
is applied; then the C-E impedance
is reduced to about 10-20 ohms. Since the col-
lector
is connected to the hot side of L5 (RX 7.8
MHz), the primary side
of L5 is in effect short-
circuited
and so the pulse noise is eliminated from
the Receive signal.
J..B. N.B. AGC CIRCUIT
In some N.B. circuits, under conditions of high
signal
and high noise, when N.B. is turned on,
there
is more noise than with N.B. off. This is due
to a lack of AGC. To prevent this effect, a portion
of the 27 MHz signal is picked off of L4 and ap-
plied through FET601 and TR601, N.B. AGC
amplifiers. This signal
is detected by 0601 and
0602 and applied through 0603 to the base of
TR 1, which drives the base into saturation. At the
same time, collector current increases, which drops
most
of Vcc across R4; thus reducing the gain of
the N.B. Amplifier chain. This AGC effectively
controls the N.B. loop
and its effect on the 27
MHz
RF amplifier circuitry. N.B. AGe is set to
operate with an incoming 27 MHz signal level of
100-500 J1 V.
L1
ANTENNA t
~ i
lel
;;
<0
o
RX. Signal
/
-/
Pulse N oi ..
Fig. 6 Noise Blanker Circuit
-14 -

ALIGNMENT OF TRANSMITTER SECTION
1. Equipment Required:
a. AF Oscillator (two required) f. Oscilloscope
b. AF VTVM (Full scale: 1V DC with RF probe)
g. RF VTVM
c. DC VOM
d. RF Power Meter
e. 50 ohm load and Attenuator
2. PROCEDURE (See page 8)
Connect Test Equipment as shown below.
STEP PRESET TO ADJUSTMENTS
1
S1, S2 : off
VRf5
USB, TX mode
2
Same as step 1 VR16
3
Same as step 2 VR4
VR6: fully CW
CT7: Max. Cap.
L30,L32
4 AF OSC1: 500
Hz
AF OSC2: 2400 Hz
L37,L39
S1 and S2: ON
5
Same as step 4 CT7
6
S1 and S2: OFF
VR8
AM, TX mode
7
S1: ON
VR6
AF osc: 10000 Hz
8 Same as step 7
VR7
9
Same as step 8 L27
10
S1 and S2 : 0FF
VR12
AM, TX mode
h. Tunable Field Strength Meter (Wave meter)
(or Spectrum Analyzer)
I. DC Power Supply (13.8 V/3 amp.)
REMARKS
Break circuit at TP4, place DC mA Meter in series. Adjust for
approximately 40 mA reading. Restore circuit.
Break
circuit at TP2, place mA Meter in series. Adjust for ap·
proximate~y 15 mA reading. Restore circuit.
Adjust
for minimum carrier leakage for both USB and LSB
on Oscilloscope (or Spectrum Analyzer, if available).
Adjust level
of OSC1 and OSC2 for 500 mV reading on AF
VTVM and then adjust coils for max. reading on RF VTVM.
Adjust for 24 volt reading on RF VTVM.
Adjust for 3.8 to 4.0 watt reading on RF Power Meter.
Adjust
output of OSC1 for 0.5 mV reading on AF VTVM
then adjust VR6 for 50% modulation on Scope.
Adjust
output of OSC1 for 200 mV reading on AF VTVM
then adjust VR7 for 95 to 98% modulation on Scope.
Adjust L27
to show min. 2nd harmonic (54 MHz) on Tunable
Field Strength Meter (or Spectrum Analyzer,
if available).
Adjust
VR12 so the TRC-449's power meter reads between
red and white area.
TRANSMITTER TEST EQUIPMENTS SETUP
AF
Oscillator
DC
Voltmeter
AF VTVM
1 R C· 4 49
T rans ceiver AN T
-15-
RF Power meter
so n Load
&
Attenuator
o 0 000

ALIGNMENT OF RECEIVER SECTION
1. Equipment Required
a. RF Signal Generator (455 kHz and 27 MHz Band, 50 ohm output impedance)
b. AF VTVM e. DC Power Supply
c. Oscilloscope f. 8 ohm load
d.
RF Voltmeter
2. Procedure (See page 8 ) Note;
Connect Test Equipment as shown below. L2
is adjusted at the factory so no adjustment should be made.
STEP
SIGNAL GENERATOR PRESET TO ADJUSTMENT
SETUP
RX, AM,
CH 19
27.185 MHz, modulated VOL. & RF Gain L3, L4, L5, L6,
1 1 kHz (30%) Control : Max. L7, L8
SQUELCH: Min.
ANL &N.B.: Off
2
Same as Step 1
Same as Step 1 VR 5
RX, USB,
CH 19
VOL. & RF Gain
3 1 kHz NO MOD Control: Max. CT 1
SQUELCH : Min.
ANL & NB :
Off
4
Same as Step 3
Same as Step 3 VR 1
RX, USB,
CH 19
Same as Step 1 VOL. &
RF Gain
5
Set RF Generator Control: Max. VR 3
level to 1 mV
SQUELCH : Max.
ANL & NB :
Off
RX, USB, CH 19
6
Same as Step 1
RF Gain Control : Max. (Volume
SQUELCH : Min. Control)
ANL & NB :
Off
RX, USB, CH 19
7
Same as Step 1 RF Gain Control : Min. VR 2
SQUELCH : Min.
ANL & NB :
Off
RX, USB, CH 19
RF Gain Control : Max.
8 23.5 MHz NO MOD SQUELCH : Min.
L1
NB : On
ANL
: Off
RECEIVER TEST EQUIPMENT SETUP
-16 -
EJ
AF
VTVM
~
Oscillo-
scope
REMARKS
Adjust
for a max. output.
Adjust for 2 volts output with
a SG output level of 0.5 /lV.
Adjust
for 2 volts output with
a SG output level of 0.25 /lV.
Adjust
for a reading of 5-9 on
the Transceiver's S-Meter,
with
SG output level of 100/lV.
Adjust
so squelch circuit just
opens with 1 mV signal.
Adjust
for 2 volts output with a
SG output level of 0.5 /lV.
Adjust
for 2 volts output with a
SG output level of 50/lV.
Adjust for max. output with
Volt-Meter connected
to TP5,
with SG output level of 2001lV.
lin
Resistor

5. TROUBLESHOOTING HINTS
UNIT WILL NOT TURN ON
1. Broken DC Power cable.
2. Fuse blown. Be sure you check the cause.
3. Defective power switch.
4. Defective wires or poor soldering in power
supply circuit.
NO RECEIVE SOUND
1. Defective RF circu it in receiver.
2. Defective Noise Blanker.
3. Defective AGC circuit.
4. Defective PLL circuit.
5. Defective antenna connector.
NO NOISE
1. Defective RX power circuit.
2. Defective RX audio circuit.
3. Defective PLL circuit and/or channel switch.
4. Defective squelch.
5. Defective PA-CB switch and/or EXT SP. Jack.
FOR MORE HINTS, SEE BELOW:
NO RECEIVE SOUND
A) Check for short circuit or broken wire in the
winding
of the output transformer{T-1) or
cold soldering between the wires and printed
circuit board. The DC resistance of the output
transformer winding is approximately 0.2
ohm on the primary side
and 0.5 ohm on the
secondary side
(use accurate V.O.M. if availa-
ble
to check this resistance).
B) Defective Audio Power IC4.
Check the
DC voltage at pin 10 of IC4. If
voltage reads approximately 7 V (supply
voltage/2), then problem
is not with th is I C.
C) Squelch is ON all the time.
If the gate voltage
of FET3 is +6 V or less
with Squelch Control in the C.C.W. position,
the Squelch
Circuit is defective. So, check the
circuits
of TR12, TR13 and TR14 and also
ground terminal of Squelch Control (VR404)
for cold soldering.
If the collector voltage of TR 12 is 6 V or
more, check the circuit of TR21 and Volume
Control (VR405).
D) If the Signal strength meter deflects when the
external antenna
is connected, you can as-
sume that RF thru IF stages are OK. So,
checks shou Id be made on detector and ANL
circuit (D10, D11 and D12).
NO TRANSMISSION
1. Broken or bad contact in microphone con-
nector .and/or push-to-talk switch.
2. Broken or bad contact in antenna connector.
3. Defective Relay.
4. Defect in power supply.
5. Defect in PLL and/or Carrier Oscillator (Im-
proper adjustment).
6. Inoperative microphone amplifier and/or bal-
anced
modulator in SSB mode.
7. Defective TX AMP.
(Between
mixer and final stage)
NO MODULATION
1. Defective microphone.
2. Defective microphone connector.
3. Defective TR20 or IC4, (AM mode.)
4. Inoperative microphone amplifier, (both AM
and SSB modes.)
If a negative voltage appears at the cathode
of D12, detector and ANL circuit should be
all right, so, check the circuit of TR 15.
If the collector voltage of TR15 is approx. 6
to 7 V, TR15 is all right.
E) No receive sound even with carrier oscillation
(7.B MHz) on USB/LSB mode.
In
case of no signal strength meter deflection
at the check
of D) above: If a RF voltage of
2V /P-P(34 MHz) or more is at the first gate
of FET1 and this frequency is as shown in
the frequency chart, the local oscillator (PLL)
shou
Id be all right.
F) Check the voltage of each part of the follow-
ing
stages: TR9, TRB, TR6, FET1, TR5 and
TR4 (in this order).
NO TRANSMISSION (AM)
A) Connect the DC meter in series with DC
power cable. If reading is 1.5 A or more, you
can assume that there is contact failure be-
tween relay and antenna circuit or short
circuit between final transistor (TR43) and
antenna circuit.
If the
cu rrent reads 1.5 A or less, check prior
stages.
B) If the output voltage (7.B MHz) of carrier
oscillation (TR27, TR2B)
is 100 mV or more
at TP-9, the carrier oscillation
circuit is .all
right.
-17 -

C) If a RF voltage of 20 mV/P-P or more at the
base and 300 mV /P-P or more at the collector
of the 7.8 MHz AMP (TR7), the 7.8 MHz
AMP
is all right.
If no RF voltage is present at the base, check
D7
and D35 circuits.
D) If a RF voltage of 34 MHz, 2 V /P-P or more
is readable at the first gate of the mixer
(FET7) no problem should
be expected with
Local Oscillator.
E) Check DC and RF voltages of each of the
following circuits: TR43, TR44, TR45, FET6
and 'FET7 (in this order).
F) If voltages do not appear at the collector of
TR43 or TR44, check the regulators (TR25
or TR26). If the regulator has a DC output of
approx. 5 to 7 V. the regulator should be all
right.
NO TRANSMISSION (SSB)
A) If AM transmit and modulation are working
properly, the problem
is in the circuit of 7.8
MHz AMP (TR6) or in the
circuit of Balanced
Modulator (IC2)
or in the Microphone AMP
(TR16). .
If no RF voltage of 7.8 MHz, 50 mV /P-P
appears at pin 8 of IC2, check circuits from
TR28 to pin 8 of IC2.
If no audio signal of approx. 70 mV/rms
appears at pin 1 of IC2 under modulation,
check circuits before TR16.
B) If the voltage reading at pin 8 and pin 1 of
IC2 are correct then problems are with TR6
bias circuit or D6.
C) If the output of TR6 is produced properly
check item
D) and E) of NO TRANSMIT
(AM) above.
NO AM MODULATION
The signal in the modulation circuit flows
through IC3 -D22 -
D21 - TR20 - TR22 -IC4.
Therefore check
to determine at what stage this
signal
ceases (to isolate a defective part). If no
signal appears at pin 2
of IC3, it is probable that
there is a short circuit between the collector and
emitter of the clamping transistor (TR18) or
between the collector
and emitter of the TR19.
NO NOISE BLANKER OPERATES
A) If the RF output voltage of TP-5 is 100 mV
or less with Noise Blanker ON, when signal of
23.5 MHz 200 J1V carrier is applied to
antenna, check the RF AMP circuits (lC1)
and L1 and L2.
B) If a pulse noise is amplified to 0.7 V/P-P or
more at the base of TR3 when an ignition
noise (or pulse noise)
of 100 mV/P-P or more
is applied to the antenna, the circuits of TR1
and TR2 should be all right. And if a pulse
noise
of approx. 0.2 V/P-P is produced at the
collector
of TR3, it also is all right.
NO LED CHANNEL INDICATOR LIGHTS
A) In the event a specific channel fails to light, it
is probable that there is an open circuit in the
LED display
or bad contact in the channel
selector switch.
B) If all channels fail to light, the regulator
(TR36 &TR37)
circuit is defective.
-18-

6. PLL CIRCUIT TROUBLESHOOTING HINTS
.-- ________ N_0----l Check whether there is RF
voltage on TP8.
Yes
Check whether there is ap-
prox. 2.2 Volt reading on
Yes TP7.
Defective D44,
L16 open
or
poor soldering Defective IC5,
L
17 open or
poor soldering
Defective Crystal,
Switching
Circuit, or
TR34, 38 or 39 open or
poor soldering
Defective IC6
and/or 5V line.
Yes
Defective TR40 or
L24 or poor
soldering
Yes
Defective Xtal5
and/or I C7 or
poor soldering.
Defective
FET4
L19 open.
Yes
Yes
Check whether BCD
progr<lms on Pin 13 thru
21 of IC7 work as
specified in the Chart.
Defecti
ve
Switch.
Defective
Flexible
PCB
Yes
Defective TR30 and/or
31 or poor soldering
-19 -
Yes
Defective Pin
2, 3
or 4 of IC7 or
defective TR35 or
poor soldering
Re-align
L17
Defective IC7
Good
PLL is not
defective

7. IC, TRANSISTOR & DIODE LEAD IDENTIFICATIONS
IC-1, J,l PC577H
IC-3,
J,lPC592H2
MARKING SIDE
IC-2, MC1496N
IC-4, J,lPC1156H
IC-5, UHIC-005
MARKING SIDE
TAPERED MARKING SIDE
MARKING SIDE @
trQQ~I
IC-6, J,lPC78L05
IN
®~
COMMON CD OUT
i
FET-3,5
TLR-321
CD
CD
(j)
IC-7,
@
TR-1 ~ TR-23
TR-26
~ TR-34
TR-37
~ TR-42
TR-45
TR-601
~ "',d,b,I " ,., d~,,,,,,, .. ,.,
I ~ 12313141516 6789101112
.",I,b,b,.,,,., "
r'~I~I?!I!".'~ ..!. .! ..
• • • • • • • • DIGIT 1 DIGIT 2
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c, e, d, d2 e2 C2
ANODE ANODE
DIGIT 1 DIGIT 2
-20-
BCE
BCE
FET-l, 4, 7
o
S
):(D
Gl G2
TR-24, 25, 36
TR-43,44
FET-2, 6, 601
LED
LR-070 2R
/
~ARKrNG SIDE
CATHODE
0
DIODES: 1S2473, 1N60P
SR1K-2
====V~==::::o
CCJ
~
CATHODE MAR K
0
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0
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0