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re Engineer Claims Consumer Reports iPhone 4 Reception Problem Study Is Flawed - iPhone Hacks
From: Dave Farber <dave () farber net>
Date: Wed, 14 Jul 2010 18:21:19 -0400
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From: "David P. Reed" <dpreed () reed com> Date: July 14, 2010 3:05:06 PM EDT To: dave () farber net Cc: ip <ip () v2 listbox com> Subject: Re: [IP] Engineer Claims Consumer Reports iPhone 4 Reception Problem Study Is Flawed - iPhone Hacks
Two points made by Bob Egan, the "electromagnetic engineer" who disputes the claim, trouble me a bit. Besides that, his words seem to indicate that he has not actually read the Consumer Reports *report* itself. A scientist would not claim the testing was wrong if he had not studied the data first. However, without trying to claim that Egan or CR are right or wrong, here's what worries me about Egan's post (as quoted in the iphonehack site, there being no url to his original). 1. the iPhone 4's *antenna* is actually on the outside of the phone, capable of coupling with the human hand. There is no dispute about that. So why is Egan claiming that 20 dB of sensitivity reduction is "fantasy" because they don't connect to a functional test point inside the phone? Is he claiming that touching an antenna cannot cause signal strength to drop 20dB or more? I just tried grabbing an antenna firmly in my hand that is atached on a 900 MHz SDR receiver I happen to have set up in my lab at home, and the signal dropped as much as 40dB ... Perhaps he is just saying that he wants a more precise test to give the exact number? What if it turns out to be 40 dB in some cases and not 20 dB? Was CR wrong in that case? 2. Much is made by Evans of the need for an anechoic chamber isolated from outside influences. Hmm... do you use your phone in an anechoic chamber? Is your body (a conductive sack of salt water) not in contact with the phone? What about the car you are sitting in when you use the phone? Hmm... I think CR's test might have been *better* than a "scientific" test in an anechoic chamber, or at least one could argue that. I'm sure that sensitivity tests with "functional test points" are done during manufacturing of the phone. Presumably the effect is not observed in the manufacturing process. So repeating the same test done during manufacturing proves nothing other than "the phone met its test specs". In the end of the day, science and engineering are not about experiments in the "lab". We design products for and study *reality*. Labs are just ways to set up simplistic cases, and are quite useful for that - but most scientists realize that to run a test in isolation risks missing really important effects, and most design engineers do also. On 07/14/2010 12:48 PM, Dave Farber wrote:http://www.iphonehacks.com/2010/07/radio-engineer-claims-consumer-reports-iphone-4-reception-problem-study-is-flawed.html Btw I have found no reception issues with my iPhone 4 with or without a case. I do find a face proximity problem infrequently Dave ------------------------------------------- Archives: https://www.listbox.com/member/archive/247/=now RSS Feed: https://www.listbox.com/member/archive/rss/247/ Powered by Listbox: http://www.listbox.com
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- re Engineer Claims Consumer Reports iPhone 4 Reception Problem Study Is Flawed - iPhone Hacks Dave Farber (Jul 14)
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