[Desire General] bubblesmoney:
-105dbm is crap and a weak signal. minimum attenuation i have ever found on the desire by holding the phone is 4dbm and max upto 20dbm but after earlier update it has never been more than 10-11dbm attenuation and now on froyo update a max of 14dbm attenuation. my phone does not have any case or cover etc so those readings are for such a phone.

you lose the signal at -113dbm as background radiation is same and not distinguishable from signal. hence if your attenuation is 14dbm then you would need a minimum of 99dbm (without holding phone) to have a signal while holding phone. if your attenuation is lesser then you can get away with weaker signal. attenuation differs in each persons hand as absorption will vary in each persons hand.

the following links with posts by me might interest you as i have explored this topic in detail and will explain dbm and asu and attenuation etc.

http://forums.moneysavingexpert.com/showthread.php?t=2523297

http://forums.moneysavingexpert.com/showthread.php?t=2581437&highlight=

http://forums.moneysavingexpert.com/showthread.php?p=35179785#post35179785

also i have commented on the anandtech article on the iphone getting a signal till 120dbm. i think the anandtech article made a fundamental error and then said iphone4 antenna is very sensitive in sensing signals till 120dbm unlike other phones. i think that is bollocks due to a fundamental error they made. see page 15 of that article comments section for my comment on this link http://www.anandtech.com/show/3821/iphone-4-redux-analyzing-apples-ios-41-signal-fix see extract from my comment there

"On GSM or UMTS frequencies (between 870 MHz to 2170MHz around the world) used the noise signal floor is between -111 to -114dbm. The signal noise floor is that strength at which the signal cannot be distinguished from background radiation.

The signal noise floor depends on the frequency of broadcast and not the device as far as i am aware. So the iphone cannot have a different noise floor compared to other mobile phones, unless Jobs got the governments all over the world to beam a special signal on a different frequency purely for the iphones!!!!

Anandtech has made a basic error in this analysis i think and consequently this whole article is wrong and meant to favour the iphone either inadvertantly or deliberately.

see post number 57 on the thread in this link for my explanation why this anandtech article is wrong http://forums.moneysavingexpert.com/showthread.php?p=35179785#post35179785

please note that -113dbm (some resources say -111 instead of -113) is the noise floor where signal is indistinguishible from background radiation. look it up in science webpages if you doubt what i say. so if the iphone shows signal to be -120dbm then that is an error. just because it shows a number does not mean that the -113 noise floor value does not exist in physics for gsm broadcast frequencies. http://en.wikipedia.org/wiki/Johnson–Nyquist_noise

see gsm freq bands for the world here http://en.wikipedia.org/wiki/GSM_frequency_bands the freq bands (GSM AND UMTS) used in uk are between 870 to 2170MHz and for that the noise floor is between -111dbm and -113dbm and for the noise floor to be 120dbm the freq would have to be in 180kilohertz which is !!!! and bull as the freq bands used are in MHz so the anandtech numbers dont add up in the 120dbm small print, as there is no 180kilohtz band for gsm in usa or uk as far as i can tell!!!! and 180khz is the freq used for AM band radio and looks like the iphone4 is getting interference from 180khz AM band radio signals too as far i can tell from what anandtech says about 120dbm etc !!! yikes!

I would be happy to be proved wrong and to learn, but from what i have shown i am right! Noise floor depends on the frequency band of transmission rather than circuitry. In the UK Cellular mobile services operate within the frequency ranges 872-960 MHz, 1710-1875 MHz and 1920 - 2170 MHz so the noise floor would be between -114 to -111dbm.

It would be similar in the USA too.

see the rest of my detailed response elsewhere on other forums (post 57 of the thread on the link) http://forums.moneysavingexpert.com/showthread.php?p=35179785#post35179785

I hope there is a response to this comment of mine, from this articles writers or some other RF engineers, as due to the reasons quoted in my ananlysis i think this article by anandtech is grossly wrong. I would be happy to stand corrected if my analysis is wrong.

yes the signals can be sensed at -120dbm but that wouldnt be signals from commercial GSM or UMTS signals, it would be some other signals sensed by the iphone4 sensors and giving a wrong reading of the signal strength. As i said earlier the signal noise floor depends on the broadcast frequency and not the handset, so this article is wrong and grossly so as it is making assumptions of the iphone4 being able to sense GSM / UMTS signals of the order of 120dbm which isnt possible for the frequencies broadcast as per the physics involved. http://en.wikipedia.org/wiki/Johnson–Nyquist_noise that or Jobs and anandtech found some way to defy physics!"