Midland 77-255og Transceiver Owners Manual

							 
1  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
						

							 
2 Your 40 channel CB represents the state of the art in high tech engineering. 
This unit is not only a full feature CB transceiver but incorporates a high 
performance 10 channel NOAA weather bureau VHF receiver. The full 10-
channel weather receiver allows use on all current and future NOAA weather 
bureau channels plus Canadian and international channels. The unit 
incorporates microprocessor controlled PLL circuitry for precise tuning and 
increased function. Receiver noise and interference can now be largely 
eliminated by the new ESP2™ noise reduction system. Also included is a 
backlighted Liquid Crystal Display (LCD) digital information center that out-
dates CB’s with LED readouts.  
How to install your 
Midland mobile CB 
 
  This transceiver may be installed in any 12 volt negative ground-
system car or truck. Almost all 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 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.  FCC part 95, Subpart D. 
6.  Owner’s Manual. 
  
						

							 
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Where to locate your CB transceiver. 
 
 
Your new Midland CB is designed to be installed under the dash or 
vertically on a console 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 located 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. 
 
Mechanical mounting 
Note: Extreme care should be exercised when drilling into dash to avoid 
damage to under-dash electronic ignition, cruise control, instrument and / or 
accessory wiring. Your unit must be mounted so as not to interfere with air 
bag (SRS) operation.
 
 
Step 1: Heeding the caution, use the mounting bracket as a template for 
marking the location of screw holes under the dash.  Use an awl, nail or 
other sharp pointed object to mark the metal. 
 
Step 2: Drill a 1/8” hole for each screw hole in the mounting bracket.  Attach 
the bracket to the dash with the 3/8” Phillips machine screws provided. 
. 
 
Step 3: Locate and secure the radio into the mounting bracket allowing 
working space for later power connections. 
 
Power wiring (negative ground only). 
 
Step 1: If you have not determined whether your vehicle has a negative or 
positive ground, do so now. Then disconnect the negative lead from the 
battery to prevent short circuits that can occur during wiring. 
 
Step 3: With negative ground, connect the red wire (the one with in-line fuse 
holder) to either the ( a ) fuse block radio circuit (filtered), ( b ) cigarette 
lighter (unfiltered for noise), or ( c ) directly to the positive post on your 
battery. 
 
   
						

							 
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(Usually, the fuse block is the most convenient connecting point. It is also 
possible to connect to the Accessory terminal on the fuse block, so that your 
CB automatically goes off when the ignition goes off, preventing accidental 
battery drainage.) 
 
The orange wire supplies power for the memory retention feature.  For the 
memory retention circuit to operate the orange wire must be connected to 
power that is not switched off by the ignition switch.  The connection point 
can be directly to the battery or an unswitched fuse on the fuse block. 
 
(Usually , the fuse block is the most convenient connecting point.  It is also 
possible to connect the red wire to the Accessory terminal on the fuse block 
or ignition switch wo that your CB automatically goes off when the ignition 
goes off, preventing a battery drain.) 
 
Note: In many new vehicles the only circuit that has noise filtering is the 
radio circuit. 
 
  Then tightly connect the black wire directly to the vehicle’s metal 
frame. A good direct metal - to - metal  ground is essential for optimum 
performance.  Installations using the cigarette lighter socket for power 
require an extra ground wire from the radio chassis to the vehicle if the radio 
is not fastened to a grounded part of the vehicle. 
 
Step 3: Plug - in the power cord to the receptacle provided on the back of the 
transceiver. 
 
Mounting the main unit. 
 
Step 1: Position the main unit between the bracket arms in line with the 
retention knobs.  Set the angle for optimum operating comfort and 
accessibility. 
 
Step 2: Tighten the retention knobs. 
 
Installation of microphone hanger. 
 
Mounting holes are provided on the microphone hanger bracket.  The 
bracket can be attached to the vehicle dash, or other convenient location. 
 
Antenna:  How to select, position install   
						

							 
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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. 
 
 
 
 
Where you locate your antenna does make a difference. 
 
Some general rules for antenna location that can aid CB performance: 
 
1.  Put your antenna 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. 
3 
4.  Keep antenna cables away from noise sources, such as the ignition 
system, gauges, electric fuel pumps, etc. 
 
5.  Make sure you have a solid metal - to - metal  ground. 
 
6.  Exercise care to prevent cable damage. 
 
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. 
 
Antenna installation. 
 
Follow the manufacturer’s installation instructions carefully. 
  
						

							 
6 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 Radio (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 or a two-way comm shop.
 
 
 
 
77-255ESP 
FUNCTION AND LOCATION OF CONTROLS  
						

							 
7 FRONT PANEL CONTROLS 
 
1. ROTARY CHANNEL SELECTOR: This easy to operate control allows 
    changing of weather or CB channel, either up or down. This control will 
    not operate when the channel “LOCK” function has been activated.  
 
2. MICROPHONE CONNECTOR: Plug in the supplied microphone to this  
    connector. The collar ring has a screw on locking ring. Push the ring onto  
    the units collar and screw on until it is tight.  
 
3. ON/OFF VOLUME: In the off position your transceiver’s power is off. Turn  
    this control clockwise to switch on the unit and adjust the volume. 
 
4. SQUELCH CONTROL: Adjust this control until background noise just   
    disappears. If the control is adjusted too far clockwise it may cause   
    muting of weaker signals. 
 
5. RF GAIN CONTROL: This control adjusts the receiver sensitivity.  Adjust  
    the control for best reception of distant or local stations.  Begin with 
    control fully clockwise. To reduce reception of unwanted distant stations,  
    turn control counter-clockwise until only desired stations are heard. 
    
6. MIC GAIN CONTROL: Rotating this control fully clockwise will result in 
    the greatest microphone output.  /rotating the control counter-clockwise  
    reduces the microphone output, improving the sound in high noise  
    environments.  This control can also be used to control optional power  
    microphone output. 
 
7. CHANNEL DISPLAY: LCD (liquid crystal display) read-out of selected CB  
    or weather channel. 
 
8,11,13. M1, M2, M3 INDICATOR: These LCD boxes are illuminated when a 
    memory button has been used to select the CB channel. 
 
9. TX INDICATOR: LCD indicator for showing the unit is transmitting. 
 
10. SCAN INDICATOR: This indicates channel scanning is operating. 
    
12. WX INDICATOR: When this indicator is illuminated it indicates your unit  
      is in the weather receive mode.  Weather channels are displayed. 
 
14. S/RF DISPLAY: LCD read-out of received signal strength and relative  
    transmitter power output.  
						

							 
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15. CB/WX: This button causes your unit to change modes between NOAA  
    weather bureau receiver and CB operation. 
16. M1, M2, M3 BUTTONS: These buttons select CB channels 
previously 
     set by the operator for quick recall. To store channels to memory: 
     a. Select the desired channel using the rotary channel selector knob. 
     b. Press and hold the memory button to be set for two seconds.  Two  
         beeps will sound when the channel is memorized. 
     c. To recall a channel for use, press the desired memory button.  The  
        memorized channel will be selected and displayed. 
 
17. SCAN BUTTON: This button when pressed and when the squelch is  
    closed causes the channels to be scanned until a signal opens the 
    squelch.  Pressing the button again cancels scanning. 
 
18. TALK BACK SWITCH: This switch allows the user to hear the 
transmitted audio as it is transmitted when it is set to “ON”.  This 
provides the operator with a means to monitor the effects of 
microphone gain adjustment and the sound of special audio effects 
units. 
       
19. ESP SWITCH: Pressing this button controls the ESP2™ audio system. 
     Channel noises are reduced and voices enhanced when ESP2™ is 
active. 
 
20. BRIGHT/DIM SWITCH: Pressing this button causes the backlighting of 
      the display to switch between dimmed and full brightness. 
 
 
BACK PANEL 
ANTENNA CONNECTOR: Connect a standard 50-ohm CB antenna to this  
      connector. 
 
S-METER JACK: A DC voltmeter may be connected to this jack for  
      precision monitoring of received signal strength. 
 
EXT SPEAKER JACK: When a speaker is connected to this jack the  
      internal speaker is by-passed. All received signals will be heard through  
      the external speaker when it is connected. The speaker connected to the   
      “EXT” jack should be rated at 8 ohms and 5 watts or more.  
						

							 
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HOW TO OPERATE YOUR TRANSCEIVER FOR CB USE 
You should become familiar with the controls and complete the preceding 
installation instructions before attempting operation of your CB. 
1. Adjust the squelch control fully counter-clockwise 
2. Rotate the on/off volume control clockwise to turn the unit on. Adjust the 
volume for a normal listening level. 
3. Select the desired channel by the rotary channel selector. Rotate the 
squelch control until the background noise is just quieted. You are now in the 
receive mode. 
 
NOTE: If the channel will not change, check that the “ 
 
 
4. To transmit press the PTT bar on the side of the microphone. Hold the 
microphone 2 to 3 inches from your lips and speak in a normal voice. 
5. To receive simply release the PTT bar. 
 
TO OPERATE YOUR TRANSCEIVER FOR WEATHER RECEIVE 
1. Follow steps 1 and 2 above. 
2. Press the “WX” button. 
3. Using the rotary channel selector select the active channel in your area. 
 
How ESP2™ works to make your CB sound better. 
 
The ESP2™ noise reduction system constantly monitors the signal strength 
and the type of noise present.  When the signal strength is too low for good 
reception, the receiver sound is automatically adjusted to dramatically reduce 
the noise that comes through the speaker.  While the noise is decreased the 
actual sounds you need to hear are increased. 
 
Skip interference can cause whistles and howling sounds.  Electrical 
interference from power lines, ignition systems or other sources can produce 
low humming and buzzing noise.  These high and low sounds are not 
needed for communications.  ESP2™ can determine the difference between 
undesired noises and sounds you want to hear and filter the noises out.   
 
These results ESP2™ can accomplish without decreasing receiver range (it 
usually increases range).  Most importantly, ESP2™ works by itself and does 
not need to be listening to other ESP2™ equipped CB’s to be 100% 
effective.  
  
						

							 
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TECHNICAL SPECIFICATIONS 
 
 
GENERAL  
 
Frequency range ..........................................................................26.965-27.405 MHz 
Channels ..............................................................................................................40 
Modulation type ...................................................................................................AM 
Antenna impedance .......................................................................................50 Ohm 
Loudspeaker ...................................................................................................8 Ohm 
Microphone ..................................................................................................Electret 
Power Supply ....................................................................13.8 VDC negative ground 
 
 
RECEIVER ( CB, 26.965-27.405 MHz ) 
 
Sensitivity at 10db S/N......................................................................................0.6 uV 
Selectivity .............................................................................................6 db @ 5 Khz 
Squelch range ......................................................................................0.5 uV-500 uV 
Audio output power ..................................................3.0 W @ 8 Ohm ( 10% distortion) 
Distortion at 1000 mV ............................................................................................3% 
Audio frequency response ........................................................................400-2400 Hz 
Intermediate frequency .......................................................I ° 10.695 MHz  II ° 455 Khz 
Spurious response ................................................................ .............more than 45 db 
 
 
TRANSMITTER  
RF Output Power ................................................................................................4.0 W 
Frequency Tolerance .........................................................................................0.005% 
Harmonic Suppression ..........................................................................More than 60 db 
Modulation ...........................................................................................AM 90% ( ± 5%) 
 
SPECIFICATION - WEATHER RECEIVER  
CHANNELS 
00 163.275
   05  162.450 
01 162.550   06  162.500 
02 162.400   07  162.525  
03 162.475   08  161.650  
04 162.425   09  161.775 
 
Sensitivity _________________________________1.0 uV for 20 db 
Audio Power _______________________________3.0 W 
Audio Load ________________________________8 ohms 
Intermediate Frequency ______________________455 Khz