Voltage

• The Cobra 142GTL features a variable voltage potentiometer that allows you to use different voltages, up to 16 volts. The factory setting is 13.8 volts. On the Cobra CB Radio Blog, CB expert Rick Lewis recommends setting the 142GTL to 14.8 volts, which will raise the output power without harming the radio.
  
  

Expanding the Channels

• On the Cobra 142GTL, plug-in quartz crystals control the channels. Replacing the 11.1125 MHz quartz crystal with a 11.3258 MHz crystal allows the unit to gain channels. The replacement procedure requires finding the MB8719 chip, typically located directly behind the channel selector, before isolating pin 10 from the ground pin and cutting the trace wire. Wiring a switch from pin 10 to the ground pin, and another from pin 11 to pin 12, completes the process.
  
  

Squelch

• Like many CB radios, the Cobra 142GTL has a squelch control that limits the background noise when no signal exists. To operate the control, you simply turn the knob until the background interference disappears.
  
  

RF Gain

• The RF Gain knob on the 142GTL works similar to, and in conjunction with, the squelch knob to zero-in on a signal. Raising the gain lets in more of a signal -- as well as more static, which is the weaker part of the signal. Lowering the gain cuts down the static but lets in less of the signal. The key is to fine-tune the knob, along with the squelch control, until you locate the desired signal.