How-To Get Your iPhone’s Signal Level in Decibels, persistently, across reboots.
1. Go to the phone app. Dial *3001#12345#* and hit call. You can’t use a directory entry for this, you must dial it.
2. You’ll end up in Field Test Mode, you can rummage around the screens for a whole ton of GSM info that I certainly don’t understand 99% of, however your signal bars will become a power reading decibels m – that’s the important part.
3. Next, force-quit:
- hold top button till shutdown-down prompt shows up
- release the top button
- hold home button until the shutdown screen clears
4. Then the signal meter will remain in lieu of the bars.
5. Even shows on the lock screen.
6. Interpretation:
Think of the number as a signal-loss; the best I’ve ever seen is -43dBm, typically in downtown Ottawa & Toronto I see -55 to -80. In the boonies, I’m lucky to get better than -95, although it’ll drop to -130. Anything less than -105 is going to be very marginal and almost useless.
7. How to get rid of it. (Why would you want to?)
- Dial *3001#12345#*
- Press the Home button
- Enjoy your five bars