Frequency Range was wanting to know if the freq. limits on the cobra 40 channel CB can be increased or expanded to transmitte and receive outside the 40 channel limit?

Mechanic688

• 204 Answers
• Posted on Jan 27, 2008

SOURCE: audio limiter

tintlady, here is the info you requested;
the AM limiter is R 276

These are the variable adjustments inside,and what they control.
VR-1 AM S-METER
VR-2 SSB S-METER
VR-3 SSB SQUELCH RANGE
VR-4 AM SQUELCH RANGE
VR-6 SSB CARRIER BALANCE
VR-7 TX OFFSET
VR-9 RF METER
VR-10 FINAL BIAS
VR-12 DRIVER BIAS
VR-13 SSB ALC
VR-14 AM HIGH POWER
VR-15 AM MODULATION METER
VR-16 AM MODULATION
VR-17 SSB POWER
VR-18 AM LOW POWER
VC1-10.240 MHz Frequency adjustment

Hope this helps you out, let me know,,Mechanic

Greg Cann

• 1114 Answers
• Posted on Aug 31, 2008

SOURCE: Cobra 75 WX ST 40-Channels Handheld CB Radio manual/antenna

Hi - You can download the manual from the link underlined in blue below:

75 WX ST

Other info here.



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Informatica

SOURCE: Cobra 29 Ltd Classic

In most cases just turning up VR4 is more then enough. Replacing the final, tr14 with another transistor requires changing many more parts to get it to work.

With a new 29, there is no need to change the final. Just turn vr4 all the way up and you will see around 20 - 25 watts. L13 won't gain you a single watt. L12 will raise the dead key, and usually you want a lower dead key for good swing. L14 will gain you a few watts, but don't adjust this unless you have a watt meter. You turn it out to increase wattage, but too much will over bias the final and shorten its life.

You hook it to a watt meter with a dummy load. Then say a steady AHHHH into the mic while keyed. Turn the slug out until the needle stops going up, then back it down to where it stopped.

The easy thing to do, and you will be pleased is just to turn VR4 up. Now, Up is counter clockwise. Its a variable resistor, so the less resistance, the more modulation. So you want to turn the VR down.

that will be more then enough.

SOURCE: Cobra Cb handheld radio model: HH-35 doesn't work

Open up the back of the radio and check the solder joint from the antenna connector. I had same problem and it was this.

Iron

• 3018 Answers
• Posted on Nov 09, 2011

SOURCE: schematic diagram of cobra 148 gtl cb radio china made

• Locate the MB8719 chip that is right behind the channel selector. Wire a SPST switch from pin 10 to ground and another from pin 11 to pin 12.
  

• Schematic http://minus.com/my8tfHQMD#1

• Channel Chart
  

• Position 1: sw1 down, sw2 down
• NORMAL CHANNELS
  

• Position 3: sw1 up, sw2 up
  

• 1=27.605 6=27.505 10=27.555 14=27.605
  
• 2=27.455 7=27.515 11=27.565 16=27.475
  
• 3=27.465 8=27.535 12=27.585 20=27.525
  
• 4=27.485 9=27.545 13=27.595 23=27.575
  
• 5=27.495
  

• Position 4: sw1 down, sw2 up
  

• 1=27.605 11=27.725 21=27.855 31=27.955
  
• 2=27.615 12=27.745 22=27.865 32=27.965
  
• 3=27.625 13=27.755 23=27.895 33=27.975
  
• 4=27.645 14=27.765 24=27.875 34=27.985