Kenwood TR 7800 User manual

TR 7800
TRIO
KENWOOD
VHF
TRANSCEIVER

SECTION 1
INSTALLATION
1 -1 INTERCONNECTION
Connect the antenna and power supply as shown in Fig. 1-1 for fixed station.
1-2 FIXED STATION Installation, [general]
Power supply (Fig. 1-1)
A Power supply (output current; 8A or more) is required. Antenna (Pig. 1-3) various types of fixed station
antennas are commercially available. Select your desired antenna according to your in-stallation space and application.
Note that the SW R of your antenna should be less than 1 5 A high SWR will cause the TR-7800 protective circuit to
operate, reducing the transmit output power.

1-3. MOBILE INSTALLATION, [GENERAL]
Installation location
Using the supplied mounting bracket, install the transceiver under the dashboard or on the side of the console in
your car. - Refer to Fig. 1-2A and Fig. 1-2B.
If your car is equipped with an electronic fuel injector, the transceiver should be as far from the control
equipment as possible.
Antenna installation
Various types of antenna for 2 meter mobile operation are available. (See Fig. 1-2C)
Note:
For gutter-mount installation, the antenna bracket must be grounded to the car body as shown in Fig. 1 -2C.
Affix the antenna securely, referring to the antenna instruction.
Power supply
Connect the supplied power cord with fuse directly to the battery terminals. Connecting to the cigarette lighter
socket can cause a poor connection, and excessive voltage drop
Ignition noise
The transceiver is designed to suppress ignition noise;however, if excessive noise is present, it may be necessary
to use suppressor spark plugs (with resistors).

1 4. Back-up Power
1 With power supplied directly from the car battery, the micro computer continues operating even when the power
switch is OFF. Current drain is very low. approximately 25 mA.
2 If you wish to retain the memories even when moving the unit between the car and the fixed station, utilize a battery
back-up system. Otherwise, all the memories are cleared when the power cord is disconnected.
(1) Use four AA NiCad batteries, available Locally.
(2) Open the lower cover of the transceiver.
(3) Install the batteries into the battery case located on the left
side. making sure that polarity is correct.
(4) The batteries are charged when the power switch is turned
ON.
Charging current is about 30 mA. The battery back-up function
operates only when the power cord is disconnected.
3. Back-up is available for about 3 to 5 days. To extend the
back-up period, connect the (optional) BC-1 to the external
back-up terminal.
Note:
1. Employ the same brand batteries in the same charge condition.
2. Take the batteries away if you don't use them for a long period.
Fig. 1-4 Battery Back-up

SECTION 2.
CONTROLS AND TERMINALS
2-1. Front Panel
1. VOL/POWER
Power ON-OFF switch and volume control are combined. Turning the control fully counter clockwise will turn
the power OFF. Clockwise rotation will increase the volume. In the power OFF position, about 2.5mA current is drawn
to back-up the micro-computer, provided the power cable is connected to a constant power source. To completely disable
the transceiver, disconnect the power cable.
2. SQUELCH
The squelch control is used to eliminate noise during no-signal time. Normally, this control is adjusted clockwise
until the noise disappears and the BUSY indicator goes off (threshold level). For scan operation, this control must be set
to the threshold point.
3. TX Shift Indicator
+ (RED): By pressing the GD key on the keyboard (11). the indicator will light, indicating that transmit
frequency is switched up 600 kHz from the receive frequency. (Refer to the item FH key)
S (YELLOW): By pressing the S key on the keyboard #(11). the indicator will light, indicating that the
transceiver is operating in the simplex mode. (Refer to the item S key)
— (RED): by pressing the - key on the keyboard #(11). the indicator will light, indicating that transmit
frequency is switched down 600 kHz from the receive frequency. (Refer to the item - key)

4. Frequency Display
This LED frequency display indicates the operating frequency in 4 digits (MHz-kHz).
Example: 145.950 MHz is indicated as "5.950".
5. BUSY Indicator
This lamp will light when the squelch is open in receive mode.
6. S/RF Level meter
This LED level meter indicates receive input signal strength (S) or transmit output (RF).
7. ON AIR indicator
A light emitting diode (L E D) will light in the transmit mode.
8 CH Indicator
This LED indicator indicates the channel No (0 through 14) in 2 digits
9. HI/LOW Switch
This switch is used to set transmit output power to either 25W (high) or 5W (low).
Power is high at the normal out position, and is low at the in position.
10. MIC Connector (6-pin)
For connection of the supplied microphone.
UP 4
GND 5
NC 6
MIC connector (from FRONT PANEL)

11. Keyboard
The keyboard has the following functions (Refer to "SECTION 3. OPERATION"):
[1] – [0] (Number key):
Depress four keys to set the desired operating frequency.
Example: Depress the keys, [5].[9].[5] and [0] . The frequency display will indicate "5.950" (145.950 MHz).
[+] (+ shift key):
After setting the operating frequency, depress this key. The transmit frequency will be switched up 600 kHz from the
receive frequency.
[S] (Simplex key):
Depress this key and the transceiver will be set in simplex mode (transmit and receive frequencies are the same).
[-] (- shift key):
After setting the operating frequency, depress this key. The transmit frequency will be switched down 600 kHz from
the receive frequency
(M)(Memory key):
This is used to input desired frequencies (including ±600 kHz shift) to each channel for memory. Press the key and a
check tone will be heard.
[C] (Clear key):
By pressing this key. the frequency set by the number keys is cleared. In this case. the frequency display indicates the
frequency that was displayed before the number keys were pressed. Use this key you have mistakenly entered setting
this key is also used to release the scan operation.
[SC] (Scan key):
This is used for scan operation. Press the key when this SQUELCH (2) is ON. Auto-scan or memory-scan starts
according to the position of the KEY/M SEL switch and STEP switches.
12. KEY/M. SEL Indicator
This indicates the position of the KEY/M. SEL switch. The KEY indicator will light when the switch is
depressed, and the M. indicator will light in the out position.
13. KEY/M. SEL Switch
This switch is used to select the method of setting frequency, either by the keyboard or the memory. In the
depressed position the operating frequency can be set by the keyboard; in the normal out position, the operating
frequency can be set by using the MEMORY channel selector (16).

14. STEP Switch
Use this switch to select the steps 25kHz (button out). or 5kHz (button in) during frequency scan or microphone
UP/DOWN operation.
15. REV Switch
This switch is used to reverse the repeater shift (±600 kHz) and other transmit/receive frequencies (CH 13. 14). It
is a momentary non-lock type switch and returns to the normal out position when released.
16. MEMORY Channel Selector
This switch is used to select the desired memory channel. There are 15 memory channels. Of these, channels 0 ~
12 store frequencies including ±600 kHz shift. The other two channels. 13 and 14 are "ODD split" channels, storing
transmit and receive frequencies individually. Channel "14" is the priority channel.
17. PRIORITY ALERT Switch
This switch is used to check the priority "14" channel. Depress the switch and the priority channel can be
checked at about 6 second intervals regardless of the KEY/M. SEL switch position. Tone sounds when the priority
channel is in use.
18. PRIORITY OPER Switch
This switch is used to call up the priority ("14") channel By depressing the switch, the operating frequency is
switched to the priority channel.
19. TONE Switch
When this switch is pressed, the repeater control tone burst signal (1.750 Hz) is emitted for about 0.5 second at
the beginning of each transmission.

2-2. Rear Panel
20. ANT Terminal 2-3. Microfone
Antenna terminal. impedance. Connect an antenna of 50 ohms
21. DC Power Terminal
DC power input terminal. Connect the supplied power cord with plug. Input voltage is 13.8V DC.
Observe plus ( + ) and minus ( — ) polarity
22. EXT. BACK-UP
External power back-up terminal to retain the memories. For internal back-up operation, install four AA NiCd
batteries in the built-in battery case. Use this terminal to retain the memories for a long period of time (more than
1 week), or with the power cord disconnected.
23. EXT. SP Terminal
External speaker terminal. Connect an 8 ohms speaker using the supplied plug.
24. DWN Switch
This switch is used to step the operating frequency down during both keyboard and MEMORY Channel
operation. When pressing the switch, a tone will sound. When the DWN or UP switch is held. the frequency shirts
rapidly. Pressing both the UP and DWN switches simultaneously results in stopping the frequency control operation.
25. UP Switch.
This switch is used to step up the operating frequency in both keyboard and MEMORY channel operation.
When pressing the switch, a tone will sound.
26. PTT Switch
Press-to-talk switch used for transmission. This will also release scan operation.

SECTION 3
OPERATION
3-1 General
1. This transceiver uses a PLL synthesizer controlled by micro-computer. The operating frequency can be shifted in
either 5 kHz or 25 kHz steps.
2. Operating frequencies can be set by simply pressing the keys on the keyboard. Frequencies can also be stored in the
memory channels (15 channels).
3. Transmitter precautions
(1) The TR-7800 antenna impedance is 50 ohms. Be sure to connect an antenna of 50 ohms impedance.
(2) Check the transmit frequency before operating to insure that you do not interfer with other stations.
(3) By pressing the microphone PTT switch, the TR-7800 is set in transmit mode; the ON AIR Indicator will light
and the meter indicates transmit power. Hold the microphone about 5 cm from your mouth and speak.
4. Micro-Computer Reset (At first power-up)
If, at initial TURN-ON, an erroneous or incorrect readout is displayed, reset the MICRO-COMPUTER. This is not
an equipment malfunction.
To proceed:
(1) Disconnect the power plug from the DC power terminal (21) and after about five seconds reconnect the power
plug. Turn on the power switch (1).
(2) if BACK-UP BATTERIES INSTALLED
First remove the batteries, and reset the MICRO-COMPUTER as previously described. Reinstall the batteries.

3-2 Memory Input
The TR-7800 has two different memories; normal memory and split channel memory (including priority
memory channel).
1. Normal memory (CH 0-12)
Example: To store 145.950 MHz ( — 600 kHz shift) in CH 5.
(1) Set the KEY/M.SEL switch to the KEY position (——).
(2) Set the MEMORY channel selector (16) to the CH 5 position.
(3) Input the frequency.
[DISPLAY] Frequency before input
a) Press the [5] key (MHz digit).......
b) Press the [9] key (100 KHz digit).
c) Press the [5] key (10 kHz digit)...
d} Press the [0] key (1 kHz digit).....
(Simplex operation)
Note:
a. To input MHz digit, use the [4] and [5] keys.
b. When a wrong frequency is input by mistake, press the [C] key to clear the frequency.
The frequency display will indicate the frequency before input, Re-enter the correct frequency by pressing
the keys once again starting with the MHz digit.
c. When the 1 kHz digit key ( [0] – [4] ) is pressed. the frequency display indicates 0 .
When the ( [5]-[9] ) key is pressed, the display indicates 5.
d. Do not press any other key unitill the correct frequency is input.
e. The transceiver holds the previous frequency until the new frequency is input.
(4) Input the shift mode.
Press the [-] key (the indication changes from "S" to “-“).
(5) Store the frequency in the memory. Press the [M] key.
A tone will sound, indication data entry. Change the channel and input other frequencies in the same manner.
Note:
1. If you wish to change the shift mode from simplex. press the shift key of the desired mode.
2. When the transmit frequency is shifted ±600 kHz and it is outside the amateur band (144.000 ^ 145.995 MHz),
the transceiver operates in simplex mode.
2. Split channel memory (CH 13, 14)
Example: To store a receive frequency of 144.550 MHz and transmit frequency of 145.625 MHz in CH 14. proceed
as follows:
(1) Set the KEY/M.SEL switch (13) to the KEY position down.
(2) Set the memory channel selector (16) to CH 14.
(3) Input the receive frequency. Frequency before input:
a) Press the [4] key (MHz'digit).......... 4.
b) Press the [5] key (100 KHz digit).... 4.5
c) Press the [5] key (10 kHz digit)....... 4.55
d) Press the [0] key (1 kHz digit)......... 4.550
Note:
For frequency input precautions, refer to "Notes" in normal memory.
5
59
.595
.5.950

(4) Store the receive frequency in memory. Press the (M)key.
A continuous tone will sound, indicating transmit frequency is ready to be accepted
Note:
1. The tone will sound intermittently until the transmit frequency is stored in memory.
2. When the receive frequency is stored. transmit frequency before the split (CH 14) is indicated.
(5) Input the transmit frequency
a) Press the [5] key ;MHz digit).. .... . .5
b) Press the [6] key (100 kHz digit)... . 5.6
c) Press the [2] key (10 kHz digit).. .....5.62
d) Press the [5] key (1kHz digit) ........ 5.625
(6) Store the transmit frequency in memory. –
Press the (M)key (tone stops.)..........…………….. 4.550
The transceiver is now ready for split frequency operation Set the KEY/M. switch (13) to the
M. position {button up).
Note:
When the transmit frequency is stored, the frequency display indicates the receive frequency set by step (3).
3. Memory channel operation
With the KEY/M.SEL switch in the M. position (button up.). the transceiver operates on the frequency set
by the MEMORY channel selector (16).
4. Changing memory frequencies.
If you wish to change memory frequency, store a new frequency using the above procedures. The old
frequency is erased when the new frequency is stored.
3-3 SCAN (Busy stop) Operation
The SCAN operation is classified into keyboard scan, memory scan and priority channel scan. For SCAN
operation, the squelch control should be advanced to the threshold point. See 3.6 Squelch.
• KEYBOARD SCAN
1. Set the KEY/M.SEL switch (13) to the KEY position
2. Depress the [SC] key. Scan starts automatically in 25 kHz or 5 kHz steps according to the posisition of the STEP
switch (14).
3. When a signal is present, scanning stops. Scan restarts automatically about 5 seconds later.
4. To release the scan, press the [C] key (or the microphone PTT (push-to-talk) switch.
• MEMORY SCAN
1. Set the KEY/M. SEL switch (13) to the M. SEL position.
2. Depress the [SC] key. The memory channels are scanned.
Scan stops and restarts the same as in the keyboard scan.
• PRIORITY CHANNEL SCAN
Depress the PRIORITY ALERT switch (17). A tone will sound and the BUSY indicator (5) will light at about 6 seconds
intervals (regardless of the KEY/M. SEL switch position) if the priority channel is in use.

3-4 PRIORITY OPER Switch
To call up the frequency stored m the priority "14" channel depress the PRIORITY OPER switch (19).
3-5 TX OFFSET and REVERSE
After setting channels by the number keys on the keyboard. press the [+] or [-] key. The transmit frequency will
be switched up or down 600 kHz from the receive frequency and the TX shift indicator (3) will illuminate. By pressing
the REV switch (15). the transmit and receive frequencies will be reversed. If, at this time. the transmit frequency is
beyond the amateur band frequency, A tone will sound and the transceiver is automatically set in simplex mode.
When the REV switch is pressed, the frequency indicated on the display is also reversed, but the TX shift indicator (3)
does not alter the indication.
3-6 SQUELCH
To eliminate the noise at no-signal condition, turn the squelch slowly clockwise until the noise disappears and
the BUSY indicator goes off (threshold point). Turn to an empty channel. The BUSY indicator will light and the speaker
will operate when a signal is received The squelch control is also used for scan operation control. If the signal is weak or
fades during mobile operation, readjust the squelch for the clearest reception.
3-7 HI/LOW Switch
For local communication, it is recommended that power be reduced to eliminate interference to other stations
and to minimize power consumption. By pressing the HI/LOW switch, transmit power is reduced from 25W to about
5W.
3-8 “S” Meter
The LED level meter functions as an "S" meter during reception and as an RF meter during transmission.
3-9 Adjustments
Refer to Fig. 3-1.

SECTION 4 - ADDITIONAL INFORMATION
4-1 General Information
Your TR-7800 has been factory aligned and tested to specification before shipment. Under normal
circumstances. the transceiver will operate in accordance with these operating instructions.
If your transceiver fails to work, contact the authorized dealer from which you purchased it for quick, reliable repair All
adjustable trimmers and coils in your transceiver were preset at the factory and should only be readjusted by a qualified
technician with proper test equipment Attempting service or alignment without factory authorization can void the
transceiver's warranty.
4-2 How the TX Final Module are Protected
Final module protection is provided by sampling the reflected power. As the reflected power is increased (higher
SWR) transmitter drive is reduced, thus decreasing input to the final module. This in turn reduces collector loss.
protecting the final transistors.
4-3 Battery Precaution
When charging your vehicle battery, or when jump-starting a dead battery ALWAYS disconnect the power
lead from the back of the transceiver.
4-4 Ordering Spare Parts
When ordering replacement or spare parts for your equipment, be sure to specify the following:
Model and serial number of your transceiver. Schematic number of the part. Printed circuit board number on which
the part is located. Part number and name, if known, and Quantity desired.
Note:
A full service manual is available as a separate publication.
4-5 Service
Should it ever become necessary to return the equipment for repair, pack in its original boxes and packing, and
include a full description of the problems involved. Also include your telephone number. You need not return accessory
items unless directly related to the service problem. Tag all returned items with your call for easy I.D. Please mention the
model and serial number of your radio in any correspondence, whether phone or written. For future reference, record
this information in the space provided on the back cover of this manual.
Note:
When claiming warranty service, please include a photocopy of the bill of sale; or other proof of
purchase showing the date of sale.

Kenwood TR 7800
Frequency range: 144-146 MHz (Europe) / 143.900-149 MHz (USA)
Mode: FM
RF Power output: Hi: 25W, Lo: 5W - Impedance: 50 ohms, SO-239
Voltage: 13.8 VDC Current drain: RX: 0.4-0.9 A, TX: Max 6 A
Dimensions (W*H*D): 175*64*206 mm Weight: 2.1 Kg

MODIFICATIONS FOR THE KENWOOD TR-7800
TR-7800 Loss of Memory
Intermittent loss of memory may be corrected by adding one resistor at the microprocessor on the control unit.
Procedure:
Remove bottom cover, 4 screws.
From the Control unit X53-1180-xx unplug the rear mounted connectors 8-11.
Remove 6 screws from the board.
Swing the unit forward.
Install a 470K ohm 1/8 watt or larger resistor from connector 11, "UP" pin, to ground. (microprocessor pin 35, PA2
port). Space is limited: Be certain not to create a solder bridge when installing the resistor.
Reverse steps 4-1 for reassembly.

TR-7800/TR-9000 Optional Ceramic Filters
FM Adjacent channel rejection in either unit may be improved by installing an optional narrow ceramic filter.
Filter Part No. -6db Bandwidth -70db Bandwidth Retail
CFK-455F L72-0304-05 +/- 6 kHz +/- 12 kHz $ 33.50
CFK-455G (CFK-455G)* +/- 4 kHz +/- 10 kHz $ 33.50
*Not original part. No computer part number.
Procedure
In the location:
TR-7800, RX unit X55-1270-10 part, L10 or TR-9000, RX unit X55-1260-11 part, CF1
To install, desolder the original filter and clear the second set of holes for the optional filter.
Solder the new filter in place.
Be sure all pins are actually soldered, and that there are no solder bridges between pins or across the printed circuit
board.
Clip the pins flush to the board, and reinstall the circuit board.
Note:
Squelch operation will vary from unit to unit with an optional narrow filter. Tighter coupling from the detector to
the squelch circuit may be tried to restore "original feel".

TR-7800 Tone pad conversion for 4th column function
Users who desire ABCD control functions may be accommodate by an alteration to the Control unit and to the
REV switch. This switch will then perform dual functions.
Procedure
Remove top and bottom covers, 4 screws each.
To free the front panel remove 4 screws securing the front panel bracket to the side frame.
Unplug 5 multiconnectors from the Control unit along the front and left edges of the board.
Remove 6 screws from the Control unit and swing the board over.
Remove and save R51 22 Kohm located between IC's Q19 and Q28. (Q28 pin 5).
Resolder this 22 Kohm resistor to Q28 pin 5, and solder another 22 Kohm resistor to Q28 pin 9. Using a short piece of
hookup wire, extend these connections t the REV switch as shown.
Connect a line from the center switch contact to the original feed point of R51, which is the B3 line.
To reassemble, reverse steps 4 through 1.
To operate the ABCD column, hold the REV switch IN and key the 3, 6, 9, or # keys. Normal 3rd column tones are
supplied when the REV switch is not depressed. The receive REV function is not altered by this change.
Note: This switch is a DPDT and many have both sets of contacts bridged. Free one set of contacts for this new function.

TR-7800 Pulse noise
Low level Pulse Noise reported in high power TX, or as a buzz from the speaker during TX, may be reduced or
eliminated by the following steps.
Procedure:
If not already present, install a shield (F11-0781-04) and two 1000pF capacitors (C52-1710-26) at the final amplifier
module M57733 as shown.
On the RX unit X55-1270-10 add three additional 1000pF caps (c52-1710-26) and one additional 470pF cap
(C52-1747-16) as shown.

TR-7800 Optional continuous charge for internal batteries
The internal batteries for memory back-up charge only when the radio is on. If the radio is used less than 2
hours a day, the internal batteries may not charge sufficiently to retain memory if the main power is disconnected. This
optional change may be made to continuously charge the internal batters from the main power source, whether the radio
is on or off.
Procedure
On the RX unit X55-1270-10, change R94 from 56 ohm to 120 ohm, ½W. Cut the foil at the input to Q27 and connect via
a 3/4" lead to the BB terminal on connector 1. Battery charge current will be 15mA nominal.
Note:
The radio should be connected directly to the vehicle battery and not through the ignition switch.
Turn the radio off before connecting or disconnecting the power cable.
For early units: Before closing the case, check clearance from the back of the battery case to the chassis.
If very close, add suitable insulation between the battery case and chassis.
Check for the presence of a 470 kohm 1/8W resistor which should be located on the bottom of the
Control unit X53-1180-xx, Connector 11, UP pin. Add if not already installed (and see Service Bulletin #829).