Do you know where we can find the 3 key WiFi specs for the i

[Liam O'Connor]

In a recent thread, there was speculation on the WiFi specs of
the Apple iPad with respect to similar non-Apple tablets; but,
no proof was provided.

This thread is intended to nail down the 3 key WiFi specs of
the Apple iPad.

To start, I ask of all ...

Do you know where we can find the 3 key WiFi specs for the iPad?
1. WiFi radio transmit power (usually specified in milliwatts or dBm)
2. WiFi radio sensitivity (usually specified in dBm)
3. WiFi antenna gain (usually specified in dBi)

 

[Liam O'Connor]

On Sat, 1 Mar 2014 13:27:53 -0800, Liam O'Connor wrote:

Do you know where we can find the 3 key WiFi specs for the iPad?
1. WiFi radio transmit power (usually specified in milliwatts or dBm)
2. WiFi radio sensitivity (usually specified in dBm)
3. WiFi antenna gain (usually specified in dBi)

Googling, I found this iPad teardown, which shows the hardware:
http://www.ifixit.com/Teardown/iPad+Wi-Fi+Teardown/2183

The iPad uses a "Broadcom BCM4329XKUBG 802.11n WiFi" board.
http://s1.guide-images.ifixit.com/igi/V6QetUKjFdDsDYga

The WiFi antenna is right behind the Apple logo:
http://d3nevzfk7ii3be.cloudfront.net/igi/vVWXasqYpDiLQCC3

But, I didn't see the key specs listed.
So, next, I'll look at the FCC teardown.
http://www.ifixit.com/Teardown/iPad+FCC+Teardown/2197

 

[Liam O'Connor]

On Sat, 1 Mar 2014 13:33:22 -0800, Liam O'Connor wrote:

But, I didn't see the 3 key specs listed.
So, next, I'll look at the FCC teardown.
http://www.ifixit.com/Teardown/iPad+FCC+Teardown/2197

The fcc teardown report didn't contain the 3 key specs,
so, and I'm having trouble downloading the FCC SAR evaluation report:

https://fjallfoss.fcc.gov/prod/oet/forms/blobs/retrieve.cgi?attachment_id=1251290&native_or_pdf=pdf

 

[Jeff Liebermann]

On Sat, 1 Mar 2014 13:27:53 -0800, Liam O'Connor
<liamoconnor@example.com> wrote:

In a recent thread, there was speculation on the WiFi specs of
the Apple iPad with respect to similar non-Apple tablets; but,
no proof was provided.

Recent thread where? Article ID please.

This thread is intended to nail down the 3 key WiFi specs of
the Apple iPad.

To start, I ask of all ...

Do you know where we can find the 3 key WiFi specs for the iPad?
1. WiFi radio transmit power (usually specified in milliwatts or dBm)

In the FCC type certification test results. The tx power is somewhat
different for each end of the band and for different modulation nodes
(b/g/n/a). There is no single value for tx power.

For USA:
Model A1219 FCC ID: BCG E2381A
Model A1337 FCC ID: BCG E2328A
Model A1395 FCC ID: BCG A1395
Model A1396 FCC ID: BCG A1396
For the iPad 3:
Wi-Fi Only FCC ID: BCG A1416
Verizon LTE FCC ID: BCG A1403
AT&T LTE FCC ID: BCG A1430
etc...

When the FCC ID web pile stops crashing, plug the FCC ID number into:
<http://transition.fcc.gov/oet/ea/fccid/>
and you should eventually find the xmit power. I would post some
examples, but as is normal on weekends, the FCC ID site has crashed.

For the iPad 3, nominal 2.4GHz tx output is about 16dBm. For 5GHz,
it's about 17dBm, except in the UNI-1 band, where it's 13.5dBm.

>2. WiFi radio sensitivity (usually specified in dBm)

That's not easily measured. The best that can be done is to assume
that it's the same as the sensitivity of the chipset. Most iPads use
a Broadcom BCM43291HKUBC chip, which requires that you request the
data sheet from Broadcom and possibly sign and NDA. Good luck:
<https://www.broadcom.com/products/Bluetooth/Bluetooth-RF-Silicon-and-Software-Solutions/BCM4329>
Please note that the receive sensitivity is different of each mode
(b/g/n/a) and for each connection speed. Like transmit power, there
is no single value for sensitivity. Sensitivity is usually measured
with a BER (bit error rate tester) and a pile of test equipment. Check
out the various Wi-Fi test equipment vendors for app notes.

Just to make things interesting, the usable sensitivity can be reduced
by external influences, such as your hand on the antenna as in the
iPhone 4. There can also be RFI generated by the processor and
display drivers inside the iPad. Treat the specs as best case.

>3. WiFi antenna gain (usually specified in dBi)

The antennas in the various iPad mutations vary in location and type
with model number. For example, the iPad 1 has it behind the Apple
logo, which methinks is a great location.
<http://www.cultofmac.com/156848/ipad-3-wi-fi-issues-tested-worst-performance-yet-but-does-it-really-matter/>
The iPad 2 has it just to the (rear view) right of the power
connector.
<http://cdn.imore.com/sites/imore.com/files/field/image/2012/07/iPad-2-wifi-antenna-caution-area.jpg>
On the iPad 3 antenna, the wi-fi antenna is glued to the speaker,
which is not a great idea. It also looks kinda minimal:
<http://www.ifixit.com/Guide/iPad+3+4G+Wi-Fi+Antenna+Replacement/8750>
See steps 41 thru 43.
On the iPad Air, there are two antennas glued to the inside lower
back. They're the black rectangles with the coax cables in the photo:
<http://d3nevzfk7ii3be.cloudfront.net/igi/j1bWSkU3hGUAmpcU.huge>

The dual band (2.4/5GHz) antennas are possibly a PIFA (Planar Inverted
F Antenna) type. I haven't torn one apart yet to see what's inside.
It's difficult to determine the gain for such antennas without an NEC
model. This might help
<https://discussions.apple.com/thread/4866269>
Kinda looks like these numbers came from an NEC modelling program, and
not from field tests.

So, what problem are you trying to solve? Lousy sensitivity perhaps:
<https://discussions.apple.com/message/17887360#17887360>
(1400 messages). It's apparently a common problem.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sun, 02 Mar 2014 00:49:32 -0500, nospam <nospam@nospam.invalid>
wrote:

In article <jre5h9t0gi1n8vch0rf2vvv7so1ogepica@4ax.com>, Jeff
Liebermann <jeffl@cruzio.com> wrote:

Just to make things interesting, the usable sensitivity can be reduced
by external influences, such as your hand on the antenna as in the
iPhone 4. There can also be RFI generated by the processor and
display drivers inside the iPad. Treat the specs as best case.

reception on all radios is reduced with one's hand on or near the
antenna, which is why just about every device maker tells you how to
hold it, and not to put your hand near the antenna.

it's not just apple.

Correct. Except that Apple is the worst.

nope. they're about the same as everyone else. a little worse than some
and not as bad as others.

I have the numbers from my test at:
<http://802.11junk.com/jeffl/cellular/cell-test.htm>
What do you have?

Try your phone, whatever it might be. Post the signal strength in
-dbm for holding it normally, holding it with 2 fingers, and holding
it in a death grip covering the antenna.

the iphone 4 worked *better* than the 3gs it replaced, with fewer
dropped calls.

I used an iPhone 3G for about 2 years on Verizon. No dropped calls.
However, my friends with similar phones on AT&T were constantly
dropping calls. Oddly, when the problems with the iPhone 4 appeared
my friend's iPhone 3G's magically stopped dropping calls. AT&T said
they didn't change anything. What happened is that the disconnect
time was extended, so that the system could tolerate extended deep
fades as produced by the antenna grip problem.

most users didn't have a problem with the antenna according to a survey
from changewave. in fact, very few thought it was a serious problem.

Sigh. If you just bought an iPhone and someone asked if you're having
"serious" problems what would you say? I'm in the computer repair biz
and find Apple users rarely admit they have problems unless they are
totally desperate. Instead of asking if they had "serious" problems,
I wonder how the survey would look if they asked "Have you learned to
tolerate the antenna grip problems"?

apple sold the iphone 4 for three years (and still sells it in some
parts of the world). once the initial hype died down, nobody
complained.

Sure. The rubber bumpers sorta work.

it's the same damned phone. if it really was as screwed up as some
claim, there would be ongoing complaints, and there are not.

I see. If there are no complaints, there is no problem. Time for an
old anecdote. Once upon a time, I helped a friend who owned a company
that sold light pens for the PC. Included with each pen were the
usual instructions, drivers, and documentation. After shipping about
2000 light pens, someone casually mentioned that the demo software
crashed. I checked and sure enough, it crashes every time. My guess
is at least 800 users had installed the card, ran the install
software, ran the demo, watched it crash, and said absolutely nothing.
It never ceases to amaze me how much poor quality, bad software, junk
hardware, miserable design, etc the GUM (great unwashed masses) has
learned to tolerate.

Oh, yes. Nobody complains. Here's Google search for "iphone 4
dropped calls" with the date limited to the past month:
<https://www.google.com/#q=iphone+4+dropped+calls&tbs=qdr:m>
Seems to be quite a few complaints. Instead of nobody complaining,
perhaps the problem is that nobody is listening to the constant
complaints?

other phones have the same issue, if not more so:
http://www.youtube.com/watch?v=zft3-Lwh2bo
http://www.youtube.com/watch?v=c4zbQ3f7H0U

I find it interesting that you picked two videos that measure signal
strength in "bars". Both phones have pages that show signal strength
in -dBm. All I want to know is how many dB does the signal level drop
when the phone is badly gripped.

many phones say 'don't hold it wrong'
http://dontholditwrong.tumblr.com/

Yep. That's part of the wholesale repudiation of responsibility and
litigation avoidance document included with every product these days.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Michael Black]

On Sat, 1 Mar 2014, Jeff Liebermann wrote:

On Sat, 1 Mar 2014 13:27:53 -0800, Liam O'Connor
liamoconnor@example.com> wrote:

In a recent thread, there was speculation on the WiFi specs of
the Apple iPad with respect to similar non-Apple tablets; but,
no proof was provided.

Recent thread where? Article ID please.

Probably in one of the other two newsgroups. This is the guy who added
..repair to an ongoing thread, and now started this thread crossposted to
three newsgroups, still include .repair.

MIchael

 

[Jeff Liebermann]

On Sat, 01 Mar 2014 23:40:57 -0500, nospam <nospam@nospam.invalid>
wrote:

In article <r1q4h9h4ebejmas3ile66a4qb2tso4unr6@4ax.com>, Jeff
Liebermann <jeffl@cruzio.com> wrote:

When the FCC ID web pile stops crashing, plug the FCC ID number into:
http://transition.fcc.gov/oet/ea/fccid/
and you should eventually find the xmit power. I would post some
examples, but as is normal on weekends, the FCC ID site has crashed.

it's been working fine for me.

The Following Error(s) Occurred While Retrieving The Requested Page:
Date and time of error: Sun Mar 02 00:02:08 EST 2014
Requester's address: 192.168.199.13
Requester's browser type: Mozilla/5.0 (Windows NT 5.1; rv:27.0)
Gecko/20100101 Firefox/27.0
Called from: http://transition.fcc.gov/oet/ea/fccid/
Parameters specified: RequestTimeout=500
Diagnostic information: Error Executing Database Query.
weblogic.common.resourcepool.ResourceDisabledException: Pool
OETDataSource is Suspended, cannot allocate resources to
applications..
The error occurred on line 26.

the only problem i've had was during the government shutdown when it
was offline.

It belches similar errors almost every weekend when I try it.

they could have left the server running during that time. it's not like
anyone sits there and fills the requests as they come in.

I suspect that there's nobody paying attention to log files and error
messages on weekends.

Just to make things interesting, the usable sensitivity can be reduced
by external influences, such as your hand on the antenna as in the
iPhone 4. There can also be RFI generated by the processor and
display drivers inside the iPad. Treat the specs as best case.

reception on all radios is reduced with one's hand on or near the
antenna, which is why just about every device maker tells you how to
hold it, and not to put your hand near the antenna.

it's not just apple.

Correct. Except that Apple is the worst. I was referring to the
wi-fi performance, which is also affected by hand contact with the
antenna. However, I don't have numbers for wi-fi, just cellular:
<http://802.11junk.com/jeffl/cellular/cell-test.htm>
That's about 4 years old. Not much has changed. I have some guesses
as to why, but I can't prove it without destroying at least two
iPhones. Hint: To the best of knowledge, Apple iPhone 4 and 5 are
the only devices that use an untuned monopole as an antenna. Even the
iPads don't do that.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[nospam]

In article <r1q4h9h4ebejmas3ile66a4qb2tso4unr6@4ax.com>, Jeff
Liebermann <jeffl@cruzio.com> wrote:

When the FCC ID web pile stops crashing, plug the FCC ID number into:
http://transition.fcc.gov/oet/ea/fccid/
and you should eventually find the xmit power. I would post some
examples, but as is normal on weekends, the FCC ID site has crashed.

it's been working fine for me.

the only problem i've had was during the government shutdown when it
was offline.

they could have left the server running during that time. it's not like
anyone sits there and fills the requests as they come in.

....snip...

Just to make things interesting, the usable sensitivity can be reduced
by external influences, such as your hand on the antenna as in the
iPhone 4. There can also be RFI generated by the processor and
display drivers inside the iPad. Treat the specs as best case.

reception on all radios is reduced with one's hand on or near the
antenna, which is why just about every device maker tells you how to
hold it, and not to put your hand near the antenna.

it's not just apple.

 

[Liam O'Connor]

On Sat, 1 Mar 2014 14:05:27 -0800, Liam O'Connor wrote:

The fcc teardown report didn't contain the 3 key specs,
so, and I'm having trouble downloading the FCC SAR evaluation report:

I will try these suggestions kindly supplied in the other thread:
> I wonder if the FCC reports are available to the public?

<http://transition.fcc.gov/oet/ea/fccid/>

> It would be interesting to see what specs iPads iPhones have.

here are some numbers, plus the fcc ids so you can look up all the gory
details:

<http://www.revolutionwifi.net/2012/03/ipad-3-wi-fi-specifications.html>
<https://discussions.apple.com/thread/4866269>

 

[nospam]

In article <jre5h9t0gi1n8vch0rf2vvv7so1ogepica@4ax.com>, Jeff
Liebermann <jeffl@cruzio.com> wrote:

Just to make things interesting, the usable sensitivity can be reduced
by external influences, such as your hand on the antenna as in the
iPhone 4. There can also be RFI generated by the processor and
display drivers inside the iPad. Treat the specs as best case.

reception on all radios is reduced with one's hand on or near the
antenna, which is why just about every device maker tells you how to
hold it, and not to put your hand near the antenna.

it's not just apple.

Correct. Except that Apple is the worst.

nope. they're about the same as everyone else. a little worse than some
and not as bad as others.

I was referring to the
wi-fi performance, which is also affected by hand contact with the
antenna. However, I don't have numbers for wi-fi, just cellular:
http://802.11junk.com/jeffl/cellular/cell-test.htm
That's about 4 years old. Not much has changed. I have some guesses
as to why, but I can't prove it without destroying at least two
iPhones. Hint: To the best of knowledge, Apple iPhone 4 and 5 are
the only devices that use an untuned monopole as an antenna. Even the
iPads don't do that.

the iphone 4 worked *better* than the 3gs it replaced, with fewer
dropped calls.

most users didn't have a problem with the antenna according to a survey
from changewave. in fact, very few thought it was a serious problem.

apple sold the iphone 4 for three years (and still sells it in some
parts of the world). once the initial hype died down, nobody
complained.

it's the same damned phone. if it really was as screwed up as some
claim, there would be ongoing complaints, and there are not.

other phones have the same issue, if not more so:
<http://www.youtube.com/watch?v=zft3-Lwh2bo>
<http://www.youtube.com/watch?v=c4zbQ3f7H0U>

many phones say 'don't hold it wrong'
<http://dontholditwrong.tumblr.com/>

 

[Liam O'Connor]

On Sat, 01 Mar 2014 16:19:40 -0800, Jeff Liebermann wrote:

For the iPad 3, nominal 2.4GHz tx output is about 16dBm.
For 5GHz, it's about 17dBm

Hi Jeff,
I haven't seen you on a.i.w all that much lately, but, I knew
you frequented s.e.r more studiously, so, I'm very glad you
stopped by to help us out.

All we want to do is nail down the iPad WiFi specs.

There is speculation that they are substandard (as compared to
similar non-Apple equipment); but let's leave that speculation
out of the factual data for now, and just figure out what it is.

I have a question about what those numbers in the quote are for.

If the transmit "output" is 16dBm at 2.4GHz and 17dBm at 5GHz,
I presume you mean sans an antenna because I don't see the
customary 3dB difference between the two numbers (which would
be entirely antenna related).

If so, the radio transmit power is roughly 40mW at 2.4GHz.
And, at 5GHz, it's roughly 50Mw.

Are my assumptions above about nominal transmit power correct?

 

[Liam O'Connor]

On Sat, 01 Mar 2014 16:19:40 -0800, Jeff Liebermann wrote:

So, what problem are you trying to solve? Lousy sensitivity perhaps:
https://discussions.apple.com/message/17887360#17887360
(1400 messages). It's apparently a common problem.

Hi Jeff,

In a word, yes.

I recently obtained an iPad for the first time in my life,
and I was shocked (and appalled) over what appears to be
lousy receiver sensitivy (as compared to non-Apple devices
in my very handsat the very same time and place).

I mentioned that in a recent a.m.i thread, where others
refuted my ad hoc observations. A few people said their
reception is just fine, and that I might have a bad unit.

Since I have anecdotal information that some/most/all Apple
devices are weak in radio reception and/or antenna gain, I
was asked to provide the details, which I didn't have.

So, the goal is merely to compare your typical iPad with
your typical non-Apple simimlar device for the three nominal
specs of:

a. Antenna gain (we can pick a single frequency for simplicity)
b. Radio sensitivity (again, we can pick a single frequency)
c. Radio transmit power (at any one frequency should be good enough)

 

[Liam O'Connor]

On Sat, 01 Mar 2014 23:13:56 -0800, Jeff Liebermann wrote:

The 3dB difference in gains between the two bands is pure coincidence.
It can be anything.

OK. Maybe I'm mistaken.

In "my" experience, when I buy, say, an 18 inch dish reflector
for a WiFi radio, there always seems to be a 3dB gain in the 5GHz
specifications as compared to the 2.4GHz specifications for
the same power setting of the radio.

I had thought that 3dB doubling of power was due to the inherent
physics behind doubling the frequency from 2.4 to 5 GHz.

 

[Jeff Liebermann]

On Sat, 1 Mar 2014 21:54:39 -0800, Liam O'Connor
<liamoconnor@example.com> wrote:

If the transmit "output" is 16dBm at 2.4GHz and 17dBm at 5GHz,
I presume you mean sans an antenna because I don't see the
customary 3dB difference between the two numbers (which would
be entirely antenna related).

The 3dB difference in gains between the two bands is pure coincidence.
It can be anything.

If so, the radio transmit power is roughly 40mW at 2.4GHz.
And, at 5GHz, it's roughly 50Mw.

<http://www.rapidtables.com/convert/power/dBm_to_mW.htm>
16dBm = 40mw
17dBm = 50mw

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Lewis]

In message <t4k5h9phl6lu2dhgidqrumsvgjhh2fe9j3@4ax.com>
Jeff Liebermann <jeffl@cruzio.com> wrote:
> I used an iPhone 3G for about 2 years on Verizon.

No you didn't. The iPhone 3G did not work on Verizon. Neither did the
iPhone 3GS. Neither did the initial iPhone 4.

--
In the 60's, people took acid to make the world appear weird. Now the
world is weird and people take Prozac to make it appear normal.

 

[Jeff Liebermann]

On Sat, 1 Mar 2014 21:54:39 -0800, Liam O'Connor
<liamoconnor@example.com> wrote:

There is speculation that they are substandard (as compared to
similar non-Apple equipment); but let's leave that speculation
out of the factual data for now, and just figure out what it is.

Which iPad? Model number or FCC ID number please. I don't like
working in the dark.

I don't think you're going to have much luck with converting
specifications to performance expectations. It's much easier to avoid
most of the math and just do a comparison with a known working device.

I suggest you install iPerf/Jperf on your iPad and on a desktop (any
OS).
For IOS:
<https://itunes.apple.com/us/app/wifi-perf/id458836095>
<http://wlanbook.com/wifiperf-iperf3-iperf-3-ios-iphone-ipod-touch-ipad-app/>
Android:
<https://play.google.com/store/apps/details?id=com.magicandroidapps.iperf>
PC (Java front end):
<https://code.google.com/p/xjperf/>
OS/X
<http://wlanbook.com/iperf3-mac-os-snow-leopard-lion-iperf/>
Tutorial:
<http://openmaniak.com/iperf.php>
Scroll to near the bottom for what Jperf looks like.

Setup a fairly fast PC or Mac desktop to act as the iPerf/Jperf
server. Test it with the iPad to see if you can get reasonable TCP
graphs. (don't bother with UDP for now). Play with it until it seems
reliable.

Now for the real test. Dive into the settings for your wireless
router and set it for 802.11g only (or b/g only) and a fixed speed of
54Mbits/sec. No 802.11n, no turbo, and no other speed enhancements.
It is critical that speed is locked to 54Mbits/sec so don't skip that
setting.

If your iPad comes with a case or keyboard, please remove them for the
test. Turn off Bluetooth as it might slow things down.

Start Jperf and start walking away from the wireless router. The
speed should be fairly constant up to about 25ft, where the graph will
likely drop rather quickly. Measure the distance. Now, do the same
thing with other IOS devices, Android devices, and laptops. The idea
is to use the signal strength and thruput while the iPad is sending or
receiving data.

Note that I haven't done this for a while and am not sure exactly what
will happen. I'll try it with my shiny new Galaxy Tab 3 7.0" tomorrow
or sometime next week.

The distances will be approximate, but it should give you a clue as to
the relative ranges of the various devices. You might see strange
results if you do it indoors, but if you put the wireless router in a
window or doorway, and do it outside, you will probably see more
stable numbers.

There are plenty of other things that can also be tested with
iPerf/Jperf but that can come later.

This test won't tell you if the iPad is meeting its own
specifications, but will tell you if it's inferior to other devices or
has a serious range problem.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sat, 1 Mar 2014 23:23:48 -0800, Liam O'Connor
<liamoconnor@example.com> wrote:

On Sat, 01 Mar 2014 23:13:56 -0800, Jeff Liebermann wrote:

The 3dB difference in gains between the two bands is pure coincidence.
It can be anything.

OK. Maybe I'm mistaken.

In "my" experience, when I buy, say, an 18 inch dish reflector
for a WiFi radio, there always seems to be a 3dB gain in the 5GHz
specifications as compared to the 2.4GHz specifications for
the same power setting of the radio.

I had thought that 3dB doubling of power was due to the inherent
physics behind doubling the frequency from 2.4 to 5 GHz.

Ok, let's grind the numbers for a dish. The gain of a dish is:

G = Pi^2 * Diameter^2 * aperture_efficiency / wavelength^2

If you multiply the wavelength by 2.4/5.7
the 5.7GHz gain will increase by 1/0.42^2 = 5.7 times.
Converting to dB, that is a gain increase of 7.5 dB.

This assumes that the feed illumination angle and efficiency remain
the same for both 2.4 and 5.7Ghz. That's a tolerable assumption for a
dish. However, it's not for a dual band PIFA antenna, which in this
case according to the specs seems to have about 4.2dB more gain at
5.7GHz than at 2.4GHz.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sat, 1 Mar 2014 22:03:03 -0800, Liam O'Connor
<liamoconnor@example.com> wrote:

>b. Radio sensitivity (again, we can pick a single frequency)

Seven years ago, I did this receiver sensitivity chart for various
wi-fi routers:
<http://802.11junk.com/jeffl/rx-sens/receiver%20sensitivity.htm>
All of the numbers came from the data sheets which amazingly matched
the chip manufacturers numbers almost exactly. That's not going to
help you get the iPad sensitivity, but I thought it might be of some
interest.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[nospam]

In article <t4k5h9phl6lu2dhgidqrumsvgjhh2fe9j3@4ax.com>, Jeff
Liebermann <jeffl@cruzio.com> wrote:

reception on all radios is reduced with one's hand on or near the
antenna, which is why just about every device maker tells you how to
hold it, and not to put your hand near the antenna.

it's not just apple.

Correct. Except that Apple is the worst.

nope. they're about the same as everyone else. a little worse than some
and not as bad as others.

I have the numbers from my test at:
http://802.11junk.com/jeffl/cellular/cell-test.htm
What do you have?

Try your phone, whatever it might be. Post the signal strength in
-dbm for holding it normally, holding it with 2 fingers, and holding
it in a death grip covering the antenna.

i have many phones here, from flip to candybar to iphone to android,
and they all drop in signal strength depending on where i hold it.

the iphone 4 worked *better* than the 3gs it replaced, with fewer
dropped calls.

I used an iPhone 3G for about 2 years on Verizon.

no you didn't.

the iphone 3g is gsm only. there is no cdma.

the iphone was an at&t exclusive until the iphone 4 cdma in early 2011.

No dropped calls.
However, my friends with similar phones on AT&T were constantly
dropping calls.

at&t had a lot of issues, especially in the bay area. there were a lot
of dropped calls well before the iphone 4, as well as shitty data
speeds. they were overloaded, big time. they didn't expect the iphone
to be as successful as it was.

in fact, at&t was the #1 complaint from iphone users early on.

Oddly, when the problems with the iPhone 4 appeared
my friend's iPhone 3G's magically stopped dropping calls. AT&T said
they didn't change anything. What happened is that the disconnect
time was extended, so that the system could tolerate extended deep
fades as produced by the antenna grip problem.

what proof do you have that's what they did, when they said they didn't
do anything?

and at the end of the day, the user doesn't care *why* a call didn't
drop, only that it didn't.

most users didn't have a problem with the antenna according to a survey
from changewave. in fact, very few thought it was a serious problem.

Sigh. If you just bought an iPhone and someone asked if you're having
"serious" problems what would you say?

depends if i'm having serious problems or not.

changewave is in the business of surveys. they ask a statistically
valid sample. the majority (by a lot) didn't have a problem.

I'm in the computer repair biz
and find Apple users rarely admit they have problems unless they are
totally desperate. Instead of asking if they had "serious" problems,
I wonder how the survey would look if they asked "Have you learned to
tolerate the antenna grip problems"?

in fact, they did ask about that, and not that many said it was
serious. i need to find the actual survey though for specifics.

apple sold the iphone 4 for three years (and still sells it in some
parts of the world). once the initial hype died down, nobody
complained.

Sure. The rubber bumpers sorta work.

those help but not required. that was mostly to get the whiners to stop
whining.

note that after the free bumper offer ended, there weren't very many
additional complaints.

it's the same damned phone. if it really was as screwed up as some
claim, there would be ongoing complaints, and there are not.

I see. If there are no complaints, there is no problem.

pretty much.

if it isn't affecting anyone, then how is it even a problem?

Time for an
old anecdote. Once upon a time, I helped a friend who owned a company
that sold light pens for the PC. Included with each pen were the
usual instructions, drivers, and documentation. After shipping about
2000 light pens, someone casually mentioned that the demo software
crashed. I checked and sure enough, it crashes every time. My guess
is at least 800 users had installed the card, ran the install
software, ran the demo, watched it crash, and said absolutely nothing.
It never ceases to amaze me how much poor quality, bad software, junk
hardware, miserable design, etc the GUM (great unwashed masses) has
learned to tolerate.

interesting story, but i don't know what that has to do with anything.

Oh, yes. Nobody complains. Here's Google search for "iphone 4
dropped calls" with the date limited to the past month:
https://www.google.com/#q=iphone+4+dropped+calls&tbs=qdr:m
Seems to be quite a few complaints. Instead of nobody complaining,
perhaps the problem is that nobody is listening to the constant
complaints?

apple has likely sold at least 100 million iphone 4 over the past 3+
years (they don't give specific model breakdowns).

they sold 51 million iphones last quarter *alone*.

the reality is that most users did not find it to be a problem. at all.

however, the number is never going to be zero. if you touch the
antenna, the signal strength will drop, just like any phone.

people like to complain.

other phones have the same issue, if not more so:
http://www.youtube.com/watch?v=zft3-Lwh2bo
http://www.youtube.com/watch?v=c4zbQ3f7H0U

I find it interesting that you picked two videos that measure signal
strength in "bars". Both phones have pages that show signal strength
in -dBm. All I want to know is how many dB does the signal level drop
when the phone is badly gripped.

i picked a couple of videos that show the effect of 'holding it wrong'.

many phones say 'don't hold it wrong'
http://dontholditwrong.tumblr.com/

Yep. That's part of the wholesale repudiation of responsibility and
litigation avoidance document included with every product these days.

or it's part of actual effects.

i have a flip phone where the instructions say how to hold it, and if i
hold it the way it says not to, the signal strength drops.

 

[Liam O'Connor]

On Sun, 02 Mar 2014 00:06:47 -0800, Jeff Liebermann wrote:

> Converting to dB, that is a gain increase of 7.5 dB.

Wow. That's six times the power, not just doubling.

I officially will give up on my prior assumption
that the power gain at 5GHz was twice that at 2.4 GHz.

It's actually 5.62 times the power!

Thanks for explaining.

The important takeaway is that the iPad antenna has
4.2dB more gain at 5.7GHz than at 2.4GHz (which means
the iPad transmits 2.6 times as much power at 5.7GHz
as it does at 2.4GHz).

Note: My conversion of dB to power factor are from here:
http://www.sengpielaudio.com/calculator-db.htm