BlackBerry Curve 8520 signal swing - RIM BlackBerry Curve 8520 Smartphone

#1 Your BlackBerry does not have sufficient Power
Check the battery charge level as shown by the battery icon on the top left of the home screen. No Power - Battery Charge Indicator does not show a charge or is very weak. The battery icon may be red. Charge the battery.
#2 You are Out of Network coverage area
Check the Signal Strength Indicator on the home screen. (1 to 5 bars, as shown below, indicating signal strength). If there is no signal, you may be out of range of the network.
If you are sure you are in range of the network, but show no signal strength, press Alt-Right Shift-Del at the same time. This will cause the BlackBerry to reacquire a network connection.
The process for this procedure is:

• Press Alt-Right Shift-Del (The Del key is also the Backspace key.)
• The screen will go blank, and an hourglass will appear. Wait for the hourglass to go away.
• The startup screen will appear. Wait for it to go away.
• A screen that says Verifying Security Software will appear. Wait for it to go away.
• Check the Radio Tower icon.