Can a Bad SIM Card Affect Cell Phone Reception?by David Wayne
Cell phones use cellular antennas to communicate over radio waves, so a bad Subscriber Identity Module doesn't affect your signal strength. However, since SIM cards contain subscriber information, a dysfunctional card can prevent you from joining your network. Only phones using the Global System for Mobiles frequency bands require SIM cards, although other phones may use SIM cards to store user data and connect to Long-Term Evolution networks.
SIM Cards and Cellular Frequency
Your SIM card determines the frequency band on which your phone communicates. Most U.S. carriers use Code Division Multiple Access networks, which don't require SIM cards but usually have SIM card slots to enable them to work in other countries. While you might be able to make voice calls with a bad SIM card on a CDMA network, LTE data connections are limited or impossible. While GSM-compliant phones work with any GSM SIM card, CDMA networks usually block unapproved phones from joining.
Replacing a Bad SIM Card
If your carrier stores contact information on your SIM card, you may be able to import it to your phone's internal memory, if the card isn't too badly damaged, and the operating system supports it. Importing SIM contacts differs between phone models, so refer to your owner's manual for your phone's method. If you have poor cellular reception, the problem is most likely caused by network coverage in your area. If you live in a city with strong service coverage, you may have a bad antenna.
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