Midland 77-250CXL User manual

77-250CXL
OWNER’S MANUAL
40-channe! mobile citizens band transceiver.

Contents
Midland 77-250CXL features__^- 5-6
Installation instructions . _ 7
Accessories included __ 7
Location selection _ 7
Mechanical mounting _ 8
Power wiring _ 8
Microphone hanger __ 9
Optional remote speaker _ 9
Optional Publjc Address Speaker _ 9
Antennas _:_ 10
Selection (minimum requirements) _ 10
Effect of location on performance _ 1 o
Installation _ 10
Tuning _ 10
Operating instructions _________ 11
Operating controls, connectors _ 12-13
Functions and uses _ 12-13
General CB information_ 14
Channel 9 usage _ 14
10-Code usage _ 15
Channel frequency chart_ 16
Range _ 16
ESP2 ™ noise reduction _ 16
Noise ---- 16
Trouble-shooting aids _ 17
Noise suppression __ 17
Common problems and solutions (chart) ___________ 18
Technical specifications __ 18
Written specifications _ 18
Service and Warranty information __ 19
4

Midland 77-250CXL
40-channel mobile
CB transceiver.
Features:
State-of-the-art techniques have been
used in the electronics of your new
Midland CB.
Including Midland Power performance
—with a transmitter rated for
legal maximum 4-watt output power with
high level modulation in accordance with
FCC Part 95.
Plus a highly sensitive, selective
dualconversion superheterodyne receiver
with a tuned RF stage, ceramic filters and
built in, automatic noise limiter-certified to
FCC Part 15 requirements.
Outside, it’s designed to give you the
most convenient operation possible.
No other design aspect has been given
more attention than the time and motion
-saving features built into your new radio,
microphone and mounting system.
You’ll find and enjoy the benefits of this
attention to detail all across the control
panel. For example:
• New large-scale, easy-reading
LED 40-channei indicator.
• Volume control.
• Full-range, variable squelch control.
• Variable mic gain control.
• True Analog
Signal/Power/Modulation/SWR Meter.
• SWR-CAL-S/RF meter switch.
• RF gain control.
• SWR calibrate control.
• Front-mounted, screw on deluxe
microphone.
• CB-PA switch permits use as a public
address amplifier.
• ANL (Automatic Noise Limiter) “Off”
switch. Noise blanker switch and
ESP2 ™ dynamic noise filter switch.
• Brite-Dim switch.
• Jacks for external speaker and PA
speaker.
• Precision PLL (Phase Locked Loop)
tuner.
• “Omni-Power” operation on 13.8-volt
DC, positive or negative ground.
• Fresh, attractive styling with mounting
bracket and retention knobs for easy i
stallation and removal for security.
• CH9-OFf^-CH19 Instantly selects CH9
or CH19.
5

Mic gain control
NB ON-OFF switch
CH9-OFF-CH19 switch
ESP ON-OFF switch
S/RF-SWR-CAL
Meter switch
BRITE-DIM switch
SRF/SWR meter
LED display
Channel rotary switch
RF gain
control
SWR control
Squelch
control
OFF/VOLUME control
ANL-OFF-PA siwtch
Midland 77-250CXL Mobile
CB operating controls.
6

How to install your
Midland mobile CB.
This transceiver may be installed in
any 12-volt negative or positive ground-
system car or truck. Most current U.S.
and foreign vehicles use a negative
system, but some older models and
some newer large trucks may have a
positive ground.
Check the requirements for your
vehicle before you begin installation.
Generally, you have a negative-ground
system if the minus ( —) battery terminal
is connected to the motor block. Contact
your dealer in the event you are unable to
determine your vehicle’s polarity system.
Installation and operating
accessories furnished with
your Midland Mobile CB:
1 . Easy-removal mounting bracket
system.
2 . Microphone bracket system.
3. All main-unit and microphone
mounting hardware needed for
normal installation.
4. Plug-in microphone with coil cord.
5. Owner’s Manual.
Where to locate your CB
transceiver.
Your new Midland CB is designed
to be installed under the dash of
your vehicle.
^ Safety and convenience are the
primary considerations in deciding
exactly where to locate your radio.
Caution: Be sure that the unit is locatec
so that it does not interfere with the
driver or impair access to any controls.
Connecting cables must be routed and
secured in such a manner as not to
interfere with the operation of the
brake, accelerator or other controls.
Interference from either the unit or
connecting cables may contribute to
the loss of control of the vehicle.
Also be sure the CB installation
does not interfere with airbag
operation.
7

Mechanical mounting.
Step i: Heeding the caution, use the
mounting bracket as a template for
marking the location of screwholes
under your dash. Use an awl, nail or
other sharp, pointed object to mark
the metal.
Step 2: Drill a. 1/8” hole for each
screwhole in the mounting bracket.
Attach the bracket to the dash with the
3/8” Phillips machine screws provided.
Extreme care should be ‘exercised when
drilling into dash to avoid damage to
under-dash electronic ignition, cruise
control, instrument airbag, and/or accessory
wiring.
Step 3: Locate and secure the radio into
the mounting bracket allowing working
space for later power connections.
Power wiring.
Step 1: If you have not determined
whether your vehicle has a negative or
positive ground, do so now. Then
disconnect the leads from the battery
to prevent short circuits that can occur
during wiring.
Step 2; With negative ground, connect
the red wire — the one with in-line fuse
holder — to either the (a) fuse block, (b)
cigarette lighter or (c) directly to the
positive post on your battery.
(Usually, the fuse block is the most
convenient connecting point. It is also
possible to connect to the Accessory
terminal on the ignition switch, so that
your CB automatically goes off when the
ignition goes off, preventing accidental
battery drainage.)
Then tightly connect the black wire
directly to the vehicle’s metal frame.
With a positive ground, reverse the
wires, connecting the red/fuse-holder
wire to the frame, the black wire to your
DC power source. A light or meter can
be a good aid in locating a suitable
power source and ground.
In either case, a good, direct metal-to-
metal ground is essential for optimum
performance.
Step 3: Plug-in the power cord to the
receptacle provided on the back of the
transceiver.
CAR'S MOTOR BLOCK OR FIRE WALL GROUND
SOLENOID
EXAMPLE OE
NEC. GROUND 12-V DC CAR BAIT
CONNECTION ILLUSTRATION
MOST CARS S TRUCKS ARE
THIS TYPE
POSITIVE SOLENOID
POS. GROUND 12-V DC CAR BATT
CONNECTION ILLUSTRATION FEW
18-WHEELERS & OLDER CARS
8

Mounting the main unit.
Step 1; Position the main unit Step 2: Tighten the retention knob^
between the bracket arms in line with
the retention knobs. Set the angle
for optimum operating comfort and
accessibility.
Installation of microphone
hanger.
Mounting holes are provided on the
side of the transceiver for the microphone
hanger bracket. Alternately, the bracket
can be attached to the vehicle dash.
Connecting optional remote
speaker.
Locate the “EXT” jack on the main
unit rear panel. Firmly insert and seat
the speaker wire plug into the jack.
When connected, the external speaker
will override and “blank out” the in-unit
speaker standard with your Midland
Mobile CB.
Connecting optional Public
Address speaker.
Locate the “PA” jack on the main unit
back panel. Firmly insert and seat the
speaker wire plug into the jack.
Directions for mounting the optional
PA speaker are included along with
mounting hardware, with the speaker.
9

Antennas: How to select,
position, install and tune
the right one for you.
Basically, you have two types of
mobile CB antennas — full-length .
whip and loaded whip — and a variety
of types of mounts (depending on
where you locate your antenna) to
choose from.
Midland markets a broad line of
high-performance antennas. The
dealer who sold you your Midland CB
can advise which type is best for you.
Essentially, you have five location
choices: the roof, gutter, rear deck,
front cowl or rear bumper.
Where you decide to locate your
antenna will determine the type of
antenna you install. Again, consult
your Midland CB Dealer for advice and
guidance, and measure your needs
against the attributes of the various
Midland antenna models he carries.
Where you locate your antenna
does make a difference.
Some general rules for antenna
location that can aid CB performance:
1. Put your mount as high on the
vehicle as possible.
2. The higher the proportion of
antenna length that is above the
roof, the better.
3. If possible, mount the antenna in
the center of whatever surface you
choose.
4. Keep antenna cables away from
noise sources, such as the ignition
system, gauges, etc.
5. Make sure you have a solid metal-
to-metal ground.
6 . Exercise care to prevent cable
damage.
Antenna installation.
Follow the manufacturer’s
installation instructions carefully.
Warning: Never operate your CB
radio without attaching an antenna or
with a broken antenna cable. This can
result in damage to transmitter
circuitry.
Tuning your antenna.
Some antennas are factory tuned.
However, performance can usually be
improved by slightly lengthening or
shortening its length, using a Standing
Wave Ratio (SWR) meter.
For the exact procedures to be
used, refer to the antenna
manufacturer's installation manual.
You can buy an SWR meter
separately or have your antenna
checked by your Midland CB Dealer’s
service department.
10

Midland 77-250CXL
Operating Instructions
Having properly installed and wired
your CB and antenna, you are now ready
for the ten steps designed to get you you
into effective, satisfactory operation:
Step 1: Insert the plug from the
microphone into the mircrophone jack on
the face panel and screw on securely.
Step 2: Make sure your antenna is
securely connected to the antenna
connector.
Step 3:- Make sure the Squelch control
is in the 9 o'clock position.
SQUELCH
Step 4: Make sure the Mic gain control
is fully clockwise,
rvilC.GAlN
Step 5: Turn the power on and adjust
the "Volume” control for a satisfactory
sound level, volume
is fully clockwise.
RF—.GA!I\J
Step 7: Make sure the ANL/OFF/PA
switch is in the “OFF” or “ANL” positio
ANL
PA
Step 8: Put CH19-OFF-CH9 switch in
"OFF” position.
CH-'IS
CH--9
OFF
Step 9: Select your desired channel by
turning the Channel Selector dial below
the LED digital indicator clockwise (up) c
counter-clockwise (down).
Step 10: Place SRF/SWRICAL switch in
“S-RF” position.
SRF
CAL
Step 11: To transmit, press the push-to-
talk bar on the microphone. To receive,
release the bar.

Operating controls,
connectors: Their
functions and uses.
Starting at the upper left (driver's side)
of your Midland 77-250CXL and moving
counter-clockwise:
® Electronic S/RF/SWR/Modulation
Meter. This new high visibility,
meter is used four ways. (1) When
receiving, it gives tfre relative strength of
incoming signals. (2) When transmitting,
it shows RF (Radio Frequency) power
output. (3) As an “SWR” meter, it helps
match your antenna installation to your
transceiver. (4) When transmitting the
scale will peak with indicating modulation
levels.
[I] Microphone Connector. Securely
links your microphone to the main unit,
during use, yet allows quick
disconnection when out of service.
[U OffAfolume Control. Turns your CB
on and adjusts the sound level for
comfortable reception.
[C] Squelch Control. Turned clockwise, it
quiets the receiver when signals are not
being received and allows a quiet
standby operation.
The Squelch control functions only in
the receive mode and does not affect
receiver volume when signals are being
received.
To adjust, when no signals are present,
rotate the Squelch control clockwise until
the receiver is quieted.
Incoming signals will automatically
release the squelch action.
Careful adjustment is necessary as a
setting too far clockwise will not allow
weaker signals to release the squelch
action.
0 Mic (Microphone) Gain Control.
Adjusts the sensitivity of the microphone
amplifier circuit to suit individual voice
characteristics and ambient noise
conditions to provide maximum
intelligibility.
Rotating the control counter-clockwise
reduces the sensitivity and requires
“close talking” into the microphone.
VVhen operating from a noisy vehicle,
reducing the Mic Gain setting will usually
improve your transmitted voice clarity.
Check with other operators to determine
the exact setting best for your voice and
car.
0 RF Gain Control. Controls the
12