Testing the antenna issue with a voltmeter. Puzzling results...

I did a few tests to try to pinpoint the problem. We already know that it is the black line on the bottom left that is the problem area. I used a quarter for my first test. I layed my phone on its side with the left side (problem area) up. When laying the quarter over the line I lose signal fast. This we already know. I wanted to test to see if it is making the connection that is the problem. I moved the quarter so that it was right up to the black line without touching it (above the line). No loss of signal. I then barely moved the quarter so that it is over the black line but not touching the other side. This was to see if covering the black line is the issue. Still no loss of signal. I then barely moved it down a little more so that it is just barely crossing over the line. Loss of signal, down to no bars.

At this point I am thinking that making that connection is the problem. I then get my voltmeter. Here is what is strange. I did a continuity test and no matter where I touched each end on the sides it beeped letting me know it is making a loop. I could touch the top and bottom, each side, left side and top, etc. Any two places on the staneless steel regardless of the black lines. If the black lines are there to seperate the antennas then why is the entire thing connected to itself? If it is already connected, why does connecting it at the black line have an effect? I would understand if each piece was truly seperated. This makes no sense to me.

I then took speaker wire and put each end on opposite sides of the black line. When I placed the wire far apart, it had no effect. When I placed each wire on each side of the line within an inch or so of each other it caused a loss in signal. I had thought that maybe the quarter had caused an issue since it blocked the entire area where the black line is. When taking one end of the speaker wire and stretching it over the black line I lose signal. The area is not completely blocked. This tells me that it is the connection for sure. I'm just puzzled that my voltmeter reads the entire steel antenna as being connected. Anyone have any thoughts on this?

iPhone 4, iOS 4

Posted on Jun 30, 2010 2:51 AM

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11 replies

Jun 30, 2010 3:18 AM in response to Stevenam81

The current from a volt meter is direct - flowing in one direction only.

The currents for which the antennae are designed are high frequency - ie flowing back and forth rapidly.

Direct and alternating currents do not behave in the same way.

What appears like a connection to direct current can appear very high resistance to high frequency current.

Testing this with a voltmeter is meaningless.

Also the voltmeter will be putting a voltage across anything you test, and is not something I would recommend in these circumstances.

Jun 30, 2010 4:30 AM in response to Stevenam81

Stevenam81 wrote:
I then barely moved it down a little more so that it is just barely crossing over the line. Loss of signal, down to no bars.


I think this is the issue right here; what I have been saying all along.
It's not about blocking an antenna. It's not about the conductivity of the salty hands impairing the antenna from receiving the signal.

It looks to me, and your copper coin test; that simply bridging the two together causes the issue.
However much I want to believe that this can be fixed by a software update; I can't.

If A and B are separate devices. A and B work fine next to each other; but if A comes into electrical contact (conductive contact) with B, then A's functionality is impaired because (i can only guess) there is some short / feedback between the two.
Explain how a software patch could fix this?!

I really think it was a complete design flaw not to laminate / insulate the antenna with a very thin transparent coating...

I hope it can be a software issue (the firmware controlling the cipset behind the antenna) but I can't see how...

You can wrap the iPhone in your hands if you sellotape over the antenna and it doesn't lose the singal (as much) but as soon as you conductively bridge the GSM and the Wifi / BT together; bam, no signal.

Jun 30, 2010 5:16 AM in response to iZian

iZian wrote:


If A and B are separate devices. A and B work fine next to each other; but if A comes into electrical contact (conductive contact) with B, then A's functionality is impaired because (i can only guess) there is some short / feedback between the two.
*Explain how a software patch could fix this?!*


The measured impedance would change and the resultant feedback to the software controller would enable the relevant logic to take place. If the logic is not calibrated, the resultant would be an incorrect response

Jun 30, 2010 5:19 AM in response to sophos9

Exactly. If you're any good with cars, bear with me: They're all programmed to deal with a variety of running conditions at a variety of speeds and with a variety of loads. If you change something to being outside of what the control unit is programmed to be able to deal with, it does nothing to resolve it and the car runs like a bag of spanners - assuming it runs at all.

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Testing the antenna issue with a voltmeter. Puzzling results...

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