iPhone 4 Antennas are electrically connected. Implications?

[spblat]

Out of curiosity, I just put my multimeter on my iPhone across the "death grip" gap, and my reading came out to .3, which essentially means the two sections are connected. In theory, those sections should be isolated from each other and I should get a far higher reading. So that means even when I'm not holding the phone, it won't be performing as well as it should.

That is very weird and I haven't seen this observation elsewhere. I got the same result. 0.3 ohms or less across all three antenna portions, which is no different from the reading I get when I put both probes on the same antenna segment. If the steel band wasn't an antenna I'd expect it to be ground. I'm no RF engineer, but it doesn't make sense to me for those three segments to be electrically connected to each other.

Any engineering types have anything to contribute to this? Has this already been discussed?

 

[tominabox1]

That is very weird and I haven't seen this observation elsewhere. I got the same result. 0.3 ohms or less across all three antenna portions, which is no different from the reading I get when I put both probes on the same antenna segment. If the steel band wasn't an antenna I'd expect it to be ground. I'm no RF engineer, but it doesn't make sense to me for those three segments to be electrically connected to each other.

Any engineering types have anything to contribute to this? Has this already been discussed?

RF does not equal DC - many types of antennas have a DC connection like this (the details are..well technical) At RF frequencies (you know, the ones where cell networks operate) those "shorts" become less "short" and more "open." Without getting into the technical stuff I think that answers your question.

(for a more detailed example...take an inductor, its DC resistance is basically zero, but it will become highly "resistive" at a high frequency, which is inverse to a capacitor which has a DC resistance which is very high and an RF resistance that is very low...get it?)

 

[spblat]

At RF frequencies (you know, the ones where cell networks operate) those "shorts" become less "short" and more "open."

Got it. End of story. Non issue. Thanks.

 

[mgamber]

To take it just a bit further (because I'm a geek), the reason is called "skin effect". As frequency increases, power is contained to the "skin" of the conductor. At cellphone frequencies, it only uses a outermost couple of nanometers of the conductor. If the gap is at least that deep, it looks like an open circuit to the transmitter while looking like a closed circuit using a multimeter's DC source.

Skin effect is also why sticking your fingers in a 50/60 hz wall socket may well kill you while grabbing a microwave antenna will likely just burn the hell out of you. The lower frequency goes through you and may stop your heart while the very high frequency never goes deeper than a few nanometers of your body.

 

[malnar]

all three antenna portions

Two antennas.