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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 23:53:00 -0400
Begin forwarded message:
From: "DeGraff, Kenneth" <kenneth.degraff () mail house gov> Date: July 14, 2010 7:32:46 PM EDT To: dave () farber net, dpreed () reed com Subject: Re: [IP] re Engineer Claims Consumer Reports iPhone 4 Reception Problem Study Is Flawed - iPhone Hacks
For what it's worth, as a former employee of the non-profit publisher of Consumer Reports, their labs in Yonkers, NY have such an anechoic chamber on an independent foundation. They built it for speakers, but it works in this case -- as the pundit would have discovered if he had read the info they made public on their website. Inside the cage, they connected to a base station simulator commonly used in the wireless industry for testing handsets. I would be surprised if they didn't use repeatable real-world-style testing as well. But Consumer Reports is definitely not the kind of operation that would simply take some bloggers' assertions and run with them as their own. Their reputation is too important to them. =-=-=-=-=-=-=-=-=-=-=-=-=-=-= Kenneth DeGraff Legislative Director Office of Congressman Mike Doyle From: Dave Farber <dave () farber net> To: ip <ip () v2 listbox com> Sent: Wed Jul 14 18:21:19 2010 Subject: [IP] re Engineer Claims Consumer Reports iPhone 4 Reception Problem Study Is Flawed - iPhone Hacks Begin forwarded message: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 HacksTwo 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.comArchives
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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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