I have never had usable AT&T coverage on my street. So when I plugged the iPhone into the charger and got 4 bars, I was surprised.  Have conducted test calls.

However, when unplugged and on battery power, I have “No service.”

Has anyone else with marginal AT&T service seen this effect?

John Martellaro

AT&T wireless signal strength

Whenever I turn my iPhone on after being off for more than a few minutes, it shows four bars as a default, regardless of where I am, then adjusts as it acquires the network.

iPhone Signal on and off charger

I see that too.  However, when the iPhone stabilizes, I get “No Service” off the charger, however, I can easily make calls (with four or five bars showing) connected to the charger.

Two theories so far.

1. The iPhone power is reduced on battery and can’t deal with a weak signal from the closest tower.

2. The dock’s wire connection to the Mac somehow acts as an antenna.

JM

I’ve always had good coverage with Cingular/AT&T where I live.  I can’t say the same with Sprint and T Mobile, both of which I’ve had.

Ditto here.

As for the two theories posited above, I’d have to hope that it is category “2”.  What a design flaw it would be for the iPhone to lack a strong enough battery to pick up signal!

Re: iPhone Signal on and off charger

[quote author=“j.martellaro”]
Two theories so far.

1. The iPhone power is reduced on battery and can’t deal with a weak signal from the closest tower.

2. The dock’s wire connection to the Mac somehow acts as an antenna.

I experience the exact same thing with my iTrip FM transmitter and my iPod while in my car. Plugging it into the power outlet in the car gives a stronger signal.

I, too, had the same exact 2 guesses as to why this happens. I’m betting that it’s mostly #2 in both devices.

Wouldn’t a simple test to the proposed theories be to plug in yout charger to the iphone but not to the the wall outlet.

Or better yet, plug the charger into the iphone and the electrical wall outlet but turn off the circuit breaker to that branch circuit.

Then if you have a good signal we know that the battery power vs. charger power has no bearing on the signal strength since you would be using battery power only. The increase in signal, if any, would be due to the wiring.

I don’t have an iPhone, however I use to have Cingular(AT&T), and I was never able to make calls from my living room.  It worked in my back yard though..  I would venture to guess that it’s an AT&T thing and not an iPhone thing.  Good luck.

I just now got a chance to do some testing. Here’s what my tests suggest:  It’s not the juice from USB.  It’s not the USB cable.  It’s the dock alone.  Just plugging into the iPhone dock is sufficient to take me from No Service to 4 bars.

-JM

[quote author=“concerned”]Wouldn’t a simple test to the proposed theories be to plug in yout charger to the iphone but not to the the wall outlet.

Or better yet, plug the charger into the iphone and the electrical wall outlet but turn off the circuit breaker to that branch circuit.

Then if you have a good signal we know that the battery power vs. charger power has no bearing on the signal strength since you would be using battery power only. The increase in signal, if any, would be due to the wiring.

iPhone reception…

Check two things - I just had to have my first 8Gb replaced and I might need to get my 2nd one replaced…  Looks like there might be an antennae issue.

1) Warm the unit up by holding it against your body.  Regardless of the signal strength meter, check the call quality with a known good source (home voice mail, etc…).  With my first unit, if the unit was warm either from charging or being held, the call quality became unusable.

2) Start a call holding the phone “normally” with good signal strength.  Now cover the bottom half of the phone with your hands (primarily the black cover area of the bottom back).  See if your signal strength changes drastically when you cover the area with your hands.  On my new replacement, I have 5 bars with my hands away from the phone and 2 bars with my hand over the black section of the phone.  Never seen a cell phone react this way to simple hand placement - especially since the black area of the phone is where my hand typically rests when holding the phone to my head or holding the phone while using a handsfree.

Hopefully #3 will be the charm…  Everything else is great, but if I can’t get one that lets me actually hold it AND have a conversation, I have to change back to my RAZR.

Awesome post, krsnet, and welcome to the forums!

Thanks…found the site Googling for iPhone signal strength. Great site.

After reading here, I found a thread at MacRumors talking about the same issue. Looks like covering the antenna (black cover on the back) is what causes the signal drop for many. Someone was nice enough to post the Field test access code to check the actual signal strength - type in *3001#12345#* and press CALL on the phone keypad.  Selecting the “cell phone” function shows the signal strength from the local towers. The signal strength in db looks like it drops 10 to 15 db when you cover the antenna area with your hand. Tough to deal with since the antenna’s right where I normally hold the phone…

Indeed, because I am in a very low signal strength area, holding the phone with my hand wrapped around the bottom, results in no service.  However, if I hold the phone by the top, I get a signal.  As a result, I was able to make the first ever phone call on the iPhone, held in my hand, from the house. But gingerly, held at the top.

The phone has never been warm to the touch, under any conditions. And as soon as I get out of my low signal neighborhood, I can make calls just about anywhere in Denver holding the phone normally.

-JM

Me thinketh the antennae should be at the top, but then Steve didn’t ask me.