Kenwood TR-7400A User manual

INTRODUCTION
Your KENWOOD Model TR-7400A is a high-quality 2-meter transceiver for use in ama-
teur radio mobile stations as well as fixed stations. It contains a PLL frequency syn-
thesizer developed and engineered through KENWOOD's elaborate VHF technology to
provide high performance and outstanding technical characteristics.
The TR-7400A is capable of transmitting or receiving F3 FM signals on up to 800 Chan-
nels at intervals of 5 kHz, having 25W RF output power.
CONTENTS
SPECIFICATIONS ............................... 3
SECTION 1 PREPARATION FOR USE................ 4
1.1 Accessories
1.2 Tone Squelch
1.3 Antenna
1.4 Installation Caution
SECTION 2 CONTROLS AND WHAT THEY DO......... 4
2.1 Front Panel
2.2 Rear Panel
2.3 Side Panel
SECTION 3 GENERAL TIPS ON INSTALLATION........ 7
3.1 Mobile Use
3.2 Fixed-Station Use
SECTION 4 OPERATION .................. renra 8
4.1 Receiving
4.2 Transmitting
4.3 How to Use the TX Offset Switch
4.4 How to Use the Hi/Low Selector Switch
4.5 How to Use the Tone Selector Switch
4.6 Description of “Unlock” Indicator
4.7 How to Use the Tone Pad
SECTION 5 ADDITIONAL INFORMATION ...........- 12
BLOCK DIAGRAM `, 13
TOP €: BOTTOM VIEW OF THE TR-7400A ............. 14
SCHEMATIC DIAGRAM... 1... eee ee ee ees 15

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TR-7400A SPECIFICATIONS
GENERAL
Semiconductors
Frequency Range
Frequency Synthesizer
Synthesizer Stability
Mode
No. of Channel
Operating Temperature
Power Voltage
Grounding
Antenna Impedance
DC Current
Dimension
Weight
TRANSMIT. SECTION
RF Output Power
Modulation
Max. Frequency Deviation
Spurious Radiation
Touch Tone Input Impedance
Microphone
RECEIVE SECTION
Circuitry
Intermediate Frequency
Sensitivity
Squelch Sensitivity
Pass Band Width
Selectivity (2 Signal)
Image Rejection
Spurious Interference
Intermodulation
Audio Output
OPTION
i) Tone Squelch
Tone Deviation
Encorder Response
Frequency Stability
Tone Squelch Open Sensitivity
Tone Distortion
ii) Tone Burst
Burst Time
ITT TTT TTT TTT E TTT ET TT TITTEN RUND
Transistors 58
FETs 8
ICs 19
Diodes 63
144.00 to 147.995 MHz
Digital (TTL Logic) control of phase locked VCO
Less than +750 Hz at 25°C
FM
800
—20 to +50°C
11.5 VDC to 16.0 VDC
(13.8 VDC as reference)
Negative grounding
50.2
Less than 1A in receive with no input signal
Less than 8A in transmit (HI)
Less than 4.5A in transmit (LOW)
(at 13.8 VDC)
182mm (7-3/16” wide
74 mm (2-7/8) high
270 mm (10-5/8” deep
Approx. 2.8 kg (6.2 Ibs.)
High 25 watts (min.)
Low approx. 5 watts (adjustable up to 15 watts)
Variable reactance direct shift
+5 kHz
Less than —60 dB
600 2
Dynamic microphone with PTT switch, 500 Q
Double superheterodyne
ist IF 10.7 MHz
2nd IF 455 kHz
Less than 0.4 uV for 20 dB quieting
(Less than 1 uV for 30 dB S/N}
Less than 0.25 uV
More than 12 kHz at 6 dB down
More than 72 dB at 30 kHz of adjacent channel
More than 70 dB
More than 60 dB
More than 66 dB
More than 1.5 watts across 8 Q load (10% distortion)
+0.5 kHz (adjusted)
Less than 0.5 sec.
Less than +1%
Less than SINAD 10 dB
Less than 5%
Approx. 0.5 sec. (adjusted)
NOTE: The circuit and ratings may change without notice due to development in technology.

SECTION 1. PREPARATION FOR USE
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1.1 ACCESSORIES
Carefully unpack your TR-7400A Transceiver and check
that it is supplied with the following accessories:
(1) Dynamic microphone equipped with
Apin plag ari a de 1 piece
(2) Mounting bracket ........o.o.ooooo.o.. 1 piece
(3) Mounting parts
Screws, 6 mm diameter ............ 4 pieces
Plain washers, 6 mm diameter ....... 4 pieces
Spring washers, 6 mm diameter....... 4 pieces
Nuts, 6 mm diameter ............. 4 pieces
(4) Stand-off bracket .................. 1 piece
(5) babel a ee aan 1 sheet
(6) Spare fuse, IDA ................... 1 piece
(7) DC power cord with plug and fuse ...... 1 piece
(8) Miniature plug for external speaker ...... 1 piece
(9) Miniature plug for touch tone pad ...... 1 piece
(10) Plug-equipped PC board for
tonesque!lChy a mee ion a ra a 1 sheet
(11) Operating manual ................. 1 copy
1.2 TONE SQUELCH
The TR-7400A is designed not only for normal carrier type
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squeich operation, but also for tone squelch which operates
with the installation of the optional tone module. If you
operate the TR-7400A setting tone selector “SQU” without
the module, you will it not to be in the normal receive
mode. Detail is shown in page 10.
1.3 ANTENNA
Any 50 ohm 2-meter antenna system may be used with
your TR-7400A. The 50 ohm coaxial cable should be kept
as short as possible in order to minimize line loss. Attach a
UHF type connector (PL-259) to the coaxial cable for easy
connection to the receptable on the transceiver.
1.4 INSTALLATION CAUTION
Your TR-7400A Transceiver to be operated as a mobile
station should be securely mounted under the dashboard
(or similar location) using the accessory mounting bracket
and bolts. Improper installation will result in damage to
the transceiver and dashboard. Consideration must be given
to the dashboard material prior to installation. More detail-
ed information on installation will be found in SECTION
3.1, the “MOBILE USE”, page 7.
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SECTION 2. CONTROLS AND WHAT THEY DO
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Fig. 1 Front Panel View

2.1 FRONT PANEL
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POWER Switch — Turns power on when pressed in.
HI/LOW pushbutton Switch (Refer to the “HOW TO
USE THE HI/LOW SELECTOR SWITCH” section,
page 10). — Used to select high (25W) or low (5W)
RF output Power.
TONE Selector (Refer to the “HOW TO USE THE
TONE SELECTOR SWITCH” page 10). — Four posi-
tion switch used to select type of squelch desired:
SQU: Continuous tone controlled squelch (C.T.C.S.)
on transmit and receive (Optional).
OFF: Carrier Squelch operation.
BUR: Tone burst operation (Optional).
SUB: C.T.C.S. on transmit only (Optional).
Tone Squelch Indicator — A light-emitting diode (LED)
which lights when the TONE Selector is set to the
SQU position.
Meter — Indicates signal strength as an S meter during
receive and relative RF output power during transmit.
The meter function is automatically switched using the
microphone push-to-talk switch.
ON AIR Indicator — A light-emitting diode which lights
during transmit.
Repeater Indicator — A two-color light-emitting diode
which indicates the type of repeater offset. It is red
when the TX OFFSET Switch (7) is set to +600 or
green when the switch is set to —600.
Digital Frequency Display — Indicates receive frequency
only in 6 digits when the POWER Switch 0 is ON.
The display is covered with a smoked acrylic plate.
SQU Control (Outer ring) — This is a normal carrier-
type squelch control which activates the squelch cir-
cuit when turned clockwise.
VOL Control {Inner knob) — An AF volume control
used in the receive mode of operation. Clockwise
turning increases the AF volume.
MIC connector — Accepts the standard 4-pin mic.
plug supplied with the TR-7400A.
MHz Selector Switch — Used to select the desired band.
(144, 145, 146, 147 MHz indicated as 4, 5, 6, and 7
respectively).
100 kHz Selector Switch — Used to select a desired
channel in units of 100 kHz, graduated in 11 positions:
O through 9 and O.
10 kHz Selector Switch — Used to select a desired
channel in units of 10 kHz, graduated in 11 positions:
0 through 9 and 0.
5 kHz Offset Switch — Used to select the least signifi-
cant digit, 0 or 5 kHz, of the channel frequency.
Unlock Indicator, (Refer to Section 4.6 the "DESCRIP-
TION OF UNLOCK INDICATOR”, page 12).— A light-
emitting diode, indicates when the PLL circuit is in the
unlock condition. There is no synthesizer output in
the unlock condition. Note, however, that the PLL
circuit is norma! if the indicator lights momentarily
when a channel selector switch is changed.
TX OFFSET Switch (Refer to Section 4.3, the “HOW
TO USE THE TX OFFSET SWITCH”, page 9). —
This switch selects the type of frequency offset desired.
+600 kHz switches the transmit frequency
UP 600 kHz from the receive frequency.
SIMP stands for simplex operation.
The receive and transmit frequencies are the
- game.
—600 kHz automatically switches the trans-
mit frequency down 600 kHz from the receive
frequency.
2.2 REAR PANEL
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20
DC Power Connector — Accepts normal DC operating
voltage through the DC power cord supplied with the
TR-7400A.
Heat Sink — Radiates heat produced by the final tran-
sistors.
ANT Connector — For connection of any 50 ohm 2-
meter antenna.
2.3 SIDE PANEL
20
22
2
EXT SP Connector — External AF output (8 ohm).
TONE PAD Connector — A tone pad input for “Auto-
patch” operation (600 ohm — Refer to Section 4.7
the "HOW TO USE THE TONE PAD” on page 12.)
Mounting Rail — Used to install the transceiver on the
supplied mounting bracket.
Snap Lock — Used to lock the transceiver body on the
supplied mounting bracket.
Stand-off — Can be attached to your TR-7400A during
operation to provide a convenient angle of viewing for
the operator.

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SECTION 3. GENERAL TIPS ON INSTALLATION
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3.1 MOBILE USE
1. Installation Position
Your TR-7400A may be installed under the dashboard of
your vehicle for convenient operation. Be sure that its posi-
tion does not restrict your leg movement to the brake pedal.
A typical installation is shown in Fig. 4.
2. How to Install (Fig. 5)
IMPORTANT
The TR-7400A is designed for a negative ground installation.
a) Securely install the mounting bracket with the suppli-
ed bolts and nuts.
b) Insert the transceiver into the mounting bracket using
the mounting rails.
c) Adjust the rail angle for the desired position of the
transceiver. This assures operational convenience and
safety while driving the vehicle.
d) Unfold each snap lock, hook on the pawl, then clamp
the snap lock. Both locks should be fully fastened to
get full effect of the spring action.
Fig. 4 A Typical Installation
CAUTION
Be sure that both rails are fully seated in the mounting
bracket before clamping the locks.
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Slide the set into the bracket
as far as possible
o Lock Pawl
Adjust the vertical angle of the set.
Hook on the pawl and fold forward.
Fig. 5 How to Install

3. Connecting the Power Supply
Connect the supplied power cable securely from your trans-
ceiver to the battery/power supply posts. Make certain
that the red lead is placed to the positive (+) post and the
black lead to the negative (—) post. If necessary, attach
the power cable to the vehicle body at the appropriate
points to avoid dangling.
NOTES
1. The power cable should be as short as possible.
2. An alternative way of obtaining power is to plug the
cigar lighter arranged in most vehicles. Such a plug,
shown in Fig. 6, is available at auto accessory shops
or electronics parts stores.
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SECTION 4. OPERATION
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4.1 RECEIVING
1. Connect the supplied power cable to the DC power
connector (Ë and the antenna cable to the ANT con-
nector 00. Select a DC power supply or battery pack
having 8 to 10A current capacity at 13.8V.
CAUTION
Make certain that connection of the positive (+) and
negative (—) power cable leads have been connected
properly.
2. Depress the POWER ON Switch(1) The digital fre-
quency Display (8) will indicate the frequency and the
meter(5)will be illuminated.
3. Set the TONE Selector Switch(@)to OFF.
"4. Turn the SOU Control@)fully counterclockwise.
5. Turn the VOL Control clockwise until the noise
comes up to a comfortable level.
6. Set the MHz, 100 kHz and 10 kHz Selector Switches
12, 3, and 5 kHz Offset Switch (3) to the receive
frequency. If an incoming signal is received, the Meter
(S) will indicate the signal strength.
7. To eliminate the noise heard with no input signal, grad-
ually turn the SOU Control (9) clockwise until the
noise threshold is reached.
3.2 FIXED-STATION USE
If you operate the TR-7400A as a fixed station, attach the
supplied Stand-off bracket (25) to it as illustrated in Fig. 6.
The TR-7400A is designed so as to be used with a DC
power supply having a current capacity of around 10A at
the rated operating voltage of 13.8V.
Fig. 6 Use of Stand-off Bracket
NOTE
Your transceiver is normal even if the Unlock Indicator (6)
located on the center of the front panel lights momentarily
after selecting a frequency. For more detailed information,
refer to Section 4.6, the “DESCRIPTION OF UNLOCK
INDICATOR”, page 12.
4.2 TRANSMITTING
1. Plug the supplied microphone cable plug into the MIC
Connector OD.
2. Set the TONE Selector Switch@)to OFF.
Set the TX OFFSET Switch (7) to SIMP.
4. Set the MHz, 100 kHz and 10 kHz Selector Switches
(42, (9, (9 and 5 kHz Offset Switch (15) to a desired
channel.
5. Depress the microphone push-to-talk switch to operate
the TR-7400A in the transmit mode.
The ON AIR Indicator (@) will light and the meter (5)
pointer will deflect to indicate the RF output power.
6. The best separation between your mouth and micro-
phone is 5 to 10 cm.
e

NOTE
You can check the operational condition of the antenna
system by observing the reading on a standing-wave ratio
(SWR) meter. It is recommended that the antenna system
SWR is 1.5 : 1 or less.
The transmit power will be reduced by a protection circuit
when the SWR is too high. The TR-7400A is designed
so that the Meter ©) will read “8” when operating high
power (25 watts) into a 50 ohm load. The antenna system,
therefore, is acceptable if the meter reads around this value.
The meter, in this sense, acts as an SWR indicator.
4.3 HOW TO USE THE TX OFFSET SWITCH
The TX OFFSET Switch D used mainly for repeater opera-
tion, has three positions:
SIMP: Your TR-7400A operates in the usual simplex
mode. That is, the RF receive and transmit fre-
quencies are the same.
This frequency is indicated on the Digital Fre-
quency Display(8).
+600: Your Transceiver can be used for repeater opera-
tion. The Repeater indicator ) will light red.
The RF reception frequency is the same as indi-
cated on the Digital Frequency Display , but
the RF transmit frequency is 600 kHz higher than
indicated.
146.00MHz
146.010MHz 146.400 MHz
FM REPEATER
147.00MHz
146.610MHz
FM REPEATER FM REPEATER
—600: Your Transceiver can be used for repeater opera-
tion. The Repeater indicator @ will light green.
The RF receive frequency is the same as indicat-
ed on the Digital Frequency Display , but
the RF transmit frequency is 600 kHz lower than
indicated.
NOTE
The TONE Selector Switch (8) can also be used for repeater
operation. Please refer to Section 4.5, the “HOW TO USE
THE TONE SELECTOR SWITCH”, BUR position, page
10.
CAUTION
1. The TX OFFSET Switch (7), as described above,
shifts 600 kHz higher or lower only the RF transmit
frequency of your Transceiver irrespective of the posi-
tions of the MHz, 100 kHz, and 10 kHz Selector
Switches (2, (3 , (4 and 5 kHz Offset Switch (5 ,
leaving the RF receive frequency as displayed.
In general, repeater operation is done by setting the
TX OFFSET Switch (7) to +600 for the Frequency
range of 147.000 to 147.390 MHz and to —600 for
146.610 to 147.000 MHz (see Fig. 7).
2. In using the TX OFFSET Switch (7, particular care
should be observed not to transmit out of the fre-
quency band of 144 to 148 MHz.
148.00MHz
147.39 0MHz 147.600MHz 147.990 MHz
FM REPEATER
OUTPUT
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OUTPUT INPUT
AY
TR-7400A TR-7400A TR-7400A TR-7400A
TRANSMIT RECEIVE RECEIVE TRANSMIT
FREQUENCY FREQUENCY FREQUENCY FREQUENCY
< RANGE RANGE x RANGE RANGE
Ir
TX OFFSET
TX OFFSET
Fig. 7 Layout of the Two Meter Band

4.4 HOW TO USE THE HI/LOW SELECTOR
SWITCH
Occasionally, it is desirable to lower the RF transmit power
to reduce battery drain or drive an external amplifier.
Depressing the HI/LOW Selector Switch @)to LOW will
reduce the RF transmit power from 25W to 5W, which
is read as “3” approximately on the Meter (5).
4.5 HOW TO USE THE TONE SELECTOR
SWITCH
The TONE Selector Switch(3)has four positions:
SQU: Sets your transceiver to the “tone squelch” mode
of reception with the Tone Squelch Indicator @)
lit red. The tone squelch circuit built into the TR-
74004, called the “CTCS” (continuous tone con-
trolled squelch) is operated by the tone signal of a
specific frequency that has been superimposed
with the your voice signal onto the carrier in the `
TX unit and is separated in the RX unit. You may
select any desired tone frequency by choosing one
of the tone squelch active filters listed as options
available for the TR-7400A in Table 1.
Figure 9 shows installation of the tone squeich
active filter on the PC board supplied with your
TR-7400A.
Figure 8 shows installation of the PC board in the
RX unit (X55-1150-10).
Frequency (Hz) Parts number
88.5 L79-0408-05
94.8 L.79-0409-05
100.0 L79-0410-05
103.5 L79-041 1-05
107.2 L79-0412-05
110.9 L79-0413-05
114.8 L79-0414-05
118.8 L79-0415-05
123.0 L79-0416-05
127.3 L79-0417-05
131.8 L79-0418-05
136.5 L79-0419-05
141.3 L79-0420-05
146.2 L79-0421-05
151.4 L79-0422-05
156.7 L79-0423-05
Table 1 Tone Squelch Active Filter List
Bottom side
Fig. 8 How to Install the Tone Unit