I have just received my iPhone 4S ordered online. I don't have a microsim card that iPhone 4S would need to me to. I don't wish to pay extra to buy a micro sim card since it doesn't give much improvement. I did a search and found out that I could cut my ordinary 3G sim card to the size of a micro sim card. And I did this.

So now, I put that trimmed micro sim card into my iPhone 4S and it worked. But, the reception meter has only 2 bars all the time! The phone may be able to access the web and send sms through the cellular network but having only 2 out of 5 bars at the reception meter makes me feel totally unsafe; I am doing all of these at my home, where the reception signals are usually very strong.

When I put the same trimmed sim card into another iPhone 3GS, the reception also has only 2 bars. But when I put the trimmed sim card into an iPhone 2G, it has 5 bars.

What's wrong? Is it my iPhone 4S or the sim card that is having the problem? What problem am I having and what else can I do?


So the 5 signal bars on iPhone 2G is merely the 2G network. When the 2-bars 3G signal on my iPhone 4S drops to only the 2G network, it also has 4-5 bars of signal strength but that's 2G. Does trimmed SIM card has problems with 3G networks?

2 Answers 2


No - the sim card only provides an ICCID number to the phone. That number is read once per boot as the phone just uses the sim to identify what account to bill for service when registering with the nearby cell towers (IMEI and ICCID together let the system know what number to assign your phone and who to bill).

Something else must be causing your observed behavior.

Keep in mind, there is no guarantee two phones in the same location are not on distinct cell towers. Especially if one tower is overloaded or doesn't have high speed data so the phone /carrier might pick a faster connection that happens to have less bars of signal.

What does your carrier say if you call them for a site survey / diagnostic?

  • I just realise that the reason why I'm getting full signal bars on an iPhone 2G is because the network is 2G. When I get connected to a 3G network, the signal is very low and that's why the signal bars are only 2 on an iPhone 4S and 3GS. So looks like my trimmed SIM card has weak signals to 3G network. I called my carrier and the person on the phone doesn't sound like he has any solutions. Does trimmed SIM card affect 3G network connection? It shouldn't, right? Does SIM card even affect signal strength in any way?
    – xenon
    Commented Dec 1, 2011 at 7:00
  • No - either the phone reads the number (and it displays properly in the settings app) or the sim is misaligned or crushed and the phone can't read the ICCID. Once your iphone has booted, the sim isn't used by the iPhone unless you remove and re-insert it (at which point one read happens and its job is done).
    – bmike
    Commented Dec 1, 2011 at 7:06

The sim card has nothing to do with it... Its job is to provide informations about the subscriber (you), about some of the carrier specific settings and an identification mechanism. It also provides some storage for contacts and phone numbers.

Your 3G phones will simply try to connect to the closest 3G cell towers.

If they can't they will fallback to the closest GSM tower available (it can be 2G or plain GSM if 2G is not available).

Non 3G phone are not aware of 3G, so they will look for the closest 2G tower (or the closest GSM tower for a plain GSM phone). They will join the closest in their generation.

So from what you say we can conclude that where you live there must be a 2G tower nearby but the closest 3G tower if further away or the 2G signal on the tower is stronger than the 3G. So you will always get a lower signal on 3G.

If you really need stronger coverage at your house (your office is in the cellar or whatever and you are afraid to loose cell access) there are 2 solutions:

  • Ask your carrier to improve 3G/LTE coverage in your area.
  • or if you have a good internet connection at home request a FemToCel for your house.

But even if your phone looses signal it will fallback to the closest signal in the lower generations. So you shouldn't have any (major) interruptions even with lower 3G signal.

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