Detailed Tests Show iPhone 4 Signal Issues are Very Real

Submitted by lalit on July 1, 2010 - 11:31am.

Lot has been said around the blogosphere about iPhone 4 cellular reception issues. Many people have even posted videos showing the effects on signal strength caused by holding the iPhone with a left-handed grip on YouTube. Apple’s response to this problem has been largely Apple like, calling it a non-issue. However, tests done on the new iPhone by Anand Shimpi of AnandTech and Richard Gaywood clearly show that signal strength depends heavily on how you hold the phone.

In AnandTech’s tests, they observed the raw signal strength (RSSI) in dBm for the iPhone 4, iPhone 3GS and Nexus One. While holding the handsets in various position including – cupping tightly, holding naturally, resting atop an open palm, holding with a case and for baseline reading pinching the top and bottom. The results from the tests show that cupping tightly or holding naturally definitely resulted in a signal drop by as much as 24dBm for iPhone 4, which was higher than signal loss for the other two devices in same conditions.

The website wrote, “Add in an external antenna you're essentially forced to touch and bridge to another adjacent antenna while holding, and the signal attenuation is even worse. The fact of the matter is that either the most sensitive region of the antenna should have an insulative coating, or everyone should use a case. For a company that uses style heavily as a selling point, the latter isn't an option. And the former would require an unprecedented admission of fault on Apple's part.”

However, Anand concluded by saying “From my day of testing, I've determined that the iPhone 4 performs much better than the 3GS in situations where signal is very low, at -113 dBm (1 bar). Previously, dropping this low all but guaranteed that calls would drop, fail to be placed, and data would no longer be transacted at all. I can honestly say that I've never held onto so many calls and data simultaneously on 1 bar at -113 dBm as I have with the iPhone 4, so it's readily apparent that the new baseband hardware is much more sensitive compared to what was in the 3GS. The difference is that reception is massively better on the iPhone 4 in actual use.”

While AnandTech tested raw signal strength, Richard Gaywood tested the change in download speeds depending on how you hold the iPhone. He used three different holding methods – first flat on hand so the hand touches the glass back only, second held in hand in the usual manner (bare grip) and third held in hand with a piece of cloth between the hand and the phone (covered grip).

The test results showed that moving from the “flat on palm” to “covered grip” there was a small drop in download speeds. However, when the cloth was removed and the phone was held in bare hand the download performance declined sharply. According to Richard, signal attenuation happens on all the phones when you hold them in hand, but the significant change observed on iPhone only is caused by placing an electrically active antenna on the outside of the case.

“If you’re in a strong signal area, you may not ever see the effect, because even with the attenuation from holding the phone you’ll still have plenty of signal left over,” Richard wrote. “But that doesn’t mean you aren’t going to be affected by the issue unless you are never, ever in a weaker signal area.”

Richard believes that this problem won’t be fixed by a software update. He says, “People are talking about things like calibration faults in the signal strength meter, or some sort of dynamic frequency allocation that doesn’t square with any bit of the GSM spec I’ve ever been exposed too. I’m uncertain about this. It doesn’t feel like a software fault to me. But I think all of the above is unlikely. I think there’s some deeper problem here, and I await Apple’s formal response to the issue with interest.”

Like Richard we are also waiting for Apple’s formal response to the issue. However, we haven’t see any drop in call quality because of this problem (we have seen the bars go down, but the call hasn’t been affected yet), maybe because the area we are in has great 3G coverage.

We totally agree with Anand’s conclusion “The drop in signal from holding the phone with your left hand arguably remains a problem. Changing the bars visualization may indeed help mask it, and to be fair the phone works fine all the way down to -113 dBm, but it will persist - software updates can change physics as much as they can change hardware design. At the end of the day, Apple should add an insulative coating to the stainless steel band, or subsidize bumper cases. It's that simple.”