The opposite of amplification, attenuation happens whenever a signal is obstructed. All antennas — including television, radio, GPS, and cellular antennas — can experience attenuation. And with most antennas, the density and composition of the human hand can cause attenuation to a greater degree than some other materials. On a mobile phone, signal loss typically occurs when your hand attenuates the most sensitive part of the antenna. In the photos and videos below, we demonstrate how different grips cause attenuation on many popular smartphones — including iPhone 4 and iPhone 3GS.1
In our tests, iPhone 4 dropped from 3 bars to 1 bar when held in a way that attenuated the signal.
Full signal at location
Attenuated signal
The external antenna on iPhone 4 is located in the stainless steel band. The attenuation weak spot is the black strip in the lower left corner of the band.
Video (0:37): You can see the effects of attenuation starting at the 11-second mark.
Holding the phone: In weak signal areas, this grip may negatively affect signal strength.
In our tests, the BlackBerry Bold 9700 dropped from 5 bars to 1 bar when held in a way that attenuated the signal.
Full signal at location
Attenuated signal
Location of internal antenna on BlackBerry Bold 9700
Video (0:23): You can see the effects of attenuation starting
at the 7-second mark.
Holding the phone: In weak signal areas, this grip may negatively affect signal strength.
In our tests, the HTC Droid Eris dropped from 4 bars to 0 bars when held in a way that attenuated the signal.
Full signal at location
Attenuated signal
Location of main internal antenna on HTC Droid Eris
Video (0:31): You can see the effects of attenuation starting
at the 4-second mark.
Holding the phone: In weak signal areas, this grip may negatively affect signal strength.
In our tests, the Samsung Omnia II dropped from 4 bars to 1 bar when held in a way that attenuated the signal.
Full signal at location
Attenuated signal
Location of main internal antenna on Samsung Omnia II
Video (1:18): You can see the effects of attenuation starting
at the 12-second mark.
Holding the phone: In weak signal areas, this grip may negatively affect signal strength.
In our tests, iPhone 3GS dropped from 3 bars to 1 bar when held in a way that attenuated the signal.
Full signal at location
Attenuated signal
Location of internal antenna on iPhone 3GS
Video (0:35): You can see the effects of attenuation starting
at the 12-second mark.
Holding the phone: In weak signal areas, this grip may negatively affect signal strength.
Apple has invested more than $100 million building its advanced antenna design and test labs. Our engineers have logged thousands of hours designing and testing iPhone 4 in these state-of-the-art facilities. Get a look inside our labs.
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1. Tests performed on commercially available mobile phones on carrier networks with cellular signal strength between -80 dBm and -90 dBm. Testing results will vary based on site conditions.
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