Cobra's LTD 29 model Citizen's Band radio features the full 40 channels allowed and a heavy-duty microphone. The radio provides 4 watts of AM radio frequency output with a switchable automatic noise limiter and noise blanker. Other features include Cobra's Delta-Tune function. Making a Cobra LTD 29 hear and receive better involves making changes to the radio's settings, including the settings specific to this brand.
M/F Turn the switch labeled "NB/ANL, ANL, OFF" to the "ANL" position and try the transmission again if noise is affecting reception. "ANL" is an automatic noise limiter function and reduces noise caused by the vehicle's electrical systems and electronics.
M/F Switch to "NB/ANL" to activate the noise blanker, which may also reduce noise if you continue to have problems. It's an RF noise filtration function and will help with ignition noise.
M/F Adjust the "RF Gain" knob by turning it clockwise to increase gain in weak signal areas if you have problems hearing radio traffic.
M/F Set the "Delta-Tune" function to capture a more listenable signal and get rid of adjacent channel noise. Rotate the knob labeled "Deltatune" to the center position for best tuning. Try micro-adjustments to the left or right as well.
M/F Turn the volume up if you still can't hear and as with any CB radio, adjust the squelch if the radio is noisy when there's no traffic. Turn the knob labeled "Squelch" all the way to the left to receive all signals, including noise and turn the control clockwise until the background noise stops. You will be able to hear the strongest transmissions without having to listen to weak signals and noise.
The service manual can be found here