iPhone 4 External Antenna Problem

iPhone 4 External Antenna Problem

What the evidence indicates is going onSharable Shortlink

On Friday, June 25th, I tweeted a link to a YouTube video created and posted by one of my Twitter followers — @antio — whom I have every reason to believe is legitimate and well meaning. In this brief (53 second) video we see a convincing and rather horrifying demonstration of what appears to be a serious design flaw in the brand new iPhone. For your reference, here’s the YouTube video link:

iPhone External Antenna Problem

iPhone 4 Antenna Problem is Caused By a Design Flaw, Not Signal Blockage

Mentions back to me from new iPhone 4 owners were mixed, with some confirming Anthony’s demo and others unable to confirm it and being suspicious of the results.

However, as an engineer I can propose a useful theory to explain what everyone is seeing, and not seeing — and even why Apple shipped the iPhone as it is — as follows:

Simply stated, Apple’s “5-bars” cellular signal strength display is not showing the full range of possible, or even typical, received cellular signal strength. It is only showing the BOTTOM END of the full range of possible reception strength.

In other words, say for example that the iPhone is able to deliver a good clear conversation when receiving only 5% of the signal strength that you might have when standing in the shadow of a cell tower. Even though 5% signal strength is far less than 100%, if it delivers a strong and clear conversation, it’s enough. So Apple’s engineers calibrated their digital “5-bars” digital display to show all 5-bars at any signal strength from 100% all the way down to 5%. It’s only when the received signal strength begins to drop below 5% that conversations suffer, calls get dropped, and Apple starts to take bars away from their 5-bar display.

Now imagine that “bridging” the cellular and WiFi antennas by placing one’s hand across the black insulating antenna gap causes a 5% drop in received signal strength.  If you initially had, say, 80% strength, now you would be down to 75%… and you’d still have all five bars, since you still have way more than the 5% required for clear calls.  Thus, you would see and hear no effect from either deliberate or inadvertent antenna bridging.  But if you only had 5% incoming signal strength with the antenna completely in the clear — thus no remaining signal strength margin even though you were seeing 5-bars — and you then bridged the antenna, dropping the signal strength by 5% down to 0% … you would see exactly what Anthony’s video demonstrates.

It’s unfortunate that we don’t have a useful “full range” signal strength display showing us the true received power throughout its entire possible range from 100% all the way to 0% — because I believe there would be much less confusion if people could see what was actually going on.  But for now we don’t.

Whatever the case, it does appear that Apple’s latest phone, with its externalized and perhaps too accessible antennas, should be wrapped in an insulating case of some sort in order to not only keep it safe from bumps and bruises, but also to allow its antennas to operate without the attenuation created by direct contact with the phone’s owner’s body.

Steve's Sig

(Via Steve (GRC) Gibson’s Blog.)

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