Some reception produces a crackle noise and stronger ones not. This is not a squelch issue. It is a different noise, like a short in the antenna or something.

Your RF gain control needs to be turned all the way up to be able to receive signals and if you are on one of the HF bands like 40 meters or any HF band the squelch control needs to be all the way off! You do not use squelch on HF! When on VHF or UHF then you would rotate the squelch control just to the point that the background noise stops and go no further. Higher squelch settings will only block weak signals and your radio will be deaf! Squelch control rotated just to the point the background noise stops! NO SQUELCH ON HF. Turn the squelch all the way off on HF!

Plug the AC adapter into the back of the scanner and into a wall electrical outlet. Screw the antenna into the receptacle on the back of the scanner (extend the antenna to full length for best reception).

2 Set the squelch level to allow signals to be heard by turning the squelch knob counterclockwise. Rotate the volume knob clockwise until you hear static. Slowly turn the squelch knob clockwise until the static noise disappears.

3 Start programming frequencies into the scanner by pressing the "Manual" button.

4 Press the up arrow or down arrow key until the channel you wish to program is visible on the display.

5 Use the numbers on the keypad to enter the frequency for the local transmitter you wish to receive.

6 Press the "E" key to complete the process of entering the frequency.

7 Repeat steps 3 through 6 for each additional frequency you wish to monitor.

8 Press the "Scan" key to start the scanning process. The scanner stops on a channel when it detects a signal strong enough to hear over the squelch setting. Two seconds after the signal stops, the scanning process resumes.

You could install a filter in the line between the antenna and the transciever. I reccommend a high-pass or band-pass filter set for the 27 MHz band to remove any interference at different frequencies. Also, some older TVs can cause interference to CB radios if they are close. If this doesn't work, the radio may be poorly sheilded or your area may have implemented the broadband power line initiative (BPL). This produces a strong buzz of noise that obliterates all weak to moderate radio signals between 2 and 80 MHz (CB being at 27 MHz).

Make sure your squelch is not on, keep it all the way to the left and the RF Gain must be all the way to the right...

You should always connect the CB directly to the battery as the accessory socket is full of noise. You also should choose a better antenna as these small glass mounts cannot hear signals well and magnify local noise. AM (CBs) radios naturally pick up noise as it is the nature of AM signals. Use your squelch to lesson this but too much can knock out you reception.

Reception has little to do with grounding. The ground plan is for transmitting. As long as the coax is connected and is in good standing, it should receive fine regardless of grounding.

There are a few reasons you may have bad reception.

1. Turn the RF GAIN all the way up. This is your receive sensitivity.
   
2. Squelch is too high. It should only be turned up enough to cut out the background noise.
3. Poor antenna. If the antenna is cheap, and not made well, this could be the problem.
4. Not enough of the antenna above the vehicle. It needs to be at least 60% of the antenna above the vehicle.

Hope this helps!

There are two receivers and are used as "diversity" reception. That is, the strongest signal receiver output is used. As you move around, due to cancellation and reflections it is common for the diversity system to swap receivers. This is normal... HOWEVER there should not be a poplwhen it does this. You might experiment with the squelch level to improve performance. There is a possibilty there is a defect in your unit and repair would be beyond the capabilty and equipment you would have to troubleshoot the problem.

ONE thing is make sure the audio levels are turn up so the level is "not down in the noise" or in other words you have a good signal-to-noise ratio.

You have antenna or Coax Problems...

This is just a guess but sounds like your antenna connection (inside the unit) has broken. If you use the antenna as a handle it will eventually break. Radio Shack will repair it for a flat fee of $40 (that was the price the last time I checked) plus shipping. Or if you are really good at soldering and have good eye sight, you can repair it your self.
Your local radioshack should be able to send it in for repair.