Wireless Networking How do I find the antenna gain (dBi) of a Lenovo X61t laptop?

Does anyone know where I can find the dBi specification for the Lenovo
X61t laptop built-in antenna?

I'm sure it's around 1 to 3 dBi (probably 2dBi - but I'm just guessing).

I want to run realistic calculations of what signal strengths I can pick
up theoretically.

I found all the calculations that I'll run I need in these two files:
http://wndw.net/pdf/wndw2-en/wndw2-ebook.pdf
http://www.cs.uml.edu/~xinwenfu/paper/ICDCS09_Marauder_Fu.pdf

And, I found all the Lenovo X61t internal WiFi card (Intel 4965AGN)
specifications needed in this HP document:
http://tinyurl.com/76pz46a

The one thing I just can't find (which should be easy to find!) is simply
the directional & power specification (dBi) of the built-in Lenovo X61t
laptop antenna!

On Wed, 01 Feb 2012 11:09:26 +0000, Chuck Banshee wrote:


I found a picture of the antenna in situ over here:
http://www.portatronics.com/guide/PC-Laptop-Repair/lenovo-x61-repair-
guide.html

But I still can't find the antenna specifications (part number "FRU
93P4554") from this site:
http://support.lenovo.com/en_US/detail.page?LegacyDocID=MIGR-67024

On Wed, 1 Feb 2012 11:25:40 +0000 (UTC), Chuck Banshee


What are you trying to accomplish?

The blurry and distorted photo you referenced above:
<http://www.portatronics.com/guide/images/laptops/lenovox61/019.jpg>
<http://www.portatronics.com/guide/images/laptops/lenovox61/018.jpg>
appears to be some manner of PIFA antenna.  Very difficult to tell
from the photos.

These are very common in laptops as that's about all that will fit
inside the case.  If it's a PIFA, it's a 1/4 wave bent monopole above
a ground plane.  
<http://www.antenna-theory.com/antennas/patches/pifa.php>
There are many forms of the PIFA antenna.  I can't tell from the
blurry photo which one is inside the x61t.  Optimistically, it has an
average gain of about -2dBi gain at 2.4GHz.  Realistically, it's
somewhat less.

If PIFA, it's probably a dual band antenna, which is considerably more
complex:
<http://www.google.com/patents?id=w34VAAAAEBAJ>
From the polar graphs, it looks like an average gain of about -5dBi
for both 2.4 and 5.7GHz.

If you're doing calculations, don't forget about the rather high coax
cable losses.

Incidentally, the location of the antenna under the palm rest is not a
good place to hide the antenna as the signal is blocked by the nearby
metal components and shields.

--
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

On Wed, 01 Feb 2012 07:55:33 -0800, Jeff Liebermann wrote:

Hi Jeff,

You're going to be sorry you asked. :)

What I'm trying to understand is much more than just the Lenovo X61t
native antenna dBi so that's why I was hoping to just ask about that
small missing piece of the puzzle in this post.

STOP READING NOW ... BELOW IS ONLY MORE DETAIL ON THAT STATEMENT!

The bigger picture is I'm trying to figure out what real-world equipment
I need to communicate with various access points that my outdoor radio
+antenna sees (but it can't connect to them all) - and that my laptop
radio+antenna does not see (but I hope to see with a USB WiFi extender).

In addition, I'd like to add a TV antenna to the top of my WISP antenna,
so, AFTER I fully figure out the (more interesting to me) WiFi
calculations, I'll adapt them for TV signal calculations (but I don't
have ANY existing TV equipment yet to do any real-world tests).

For a WiFi example, just one (of many) interesting SSIDs found in my site
survey shows a signal strength of -89dBm with a noise of -96dBm but I
can't connect to it even though it's open. I want to calculate whether my
current equipment has the capability to connect to it, and, if not, I
want to understand how to calculate what I need to purchase
(specification wise) that will connect to it successfully.

This then leads on to the 'second step' which is to take the FCC coverage
information for TV signal to calculate what equipment I would need to
pick up certain TV stations.

For example, tvfool.com indicates PBS is on station KVIE-DT, real channel
9, virtual channel 6.1, NM=-15.4DB, Pwr=-106.9dBm, path=2edge, and
distance=82.3 miles away.

After I figure out what WiFi equipment I'd need to connect to every SSID
that is of interest to me, I'd like to then use that knowledge to figure
out what TV equipment I need to calculate what I'd need to receive NBC,
PBS, CBS, etc. at my home.

All these calculations are not something that can be easily done in a
USENET post - so - that's why I JUST asked about the laptop antenna spec.
I was just fleshing out this starting-point chart of the capabilities of
my existing equipment:

Lenovo X61t (Intel 4964AGN)
- TX=15dBm (30mW)
- RX=-90dBm@6Mbps
- Omni=2dBi ? (FRU 93P4365)

Ubiquiti Bullet M2
- TX=28dBm (630mW)
- RX=-83dBm
- Directional=19dBi

Linksys WRT54G v5 (CDFB)
- TX=18dBm (63mW)
- RX=-65dBm for 11g@54Mbps, -80db for 11b 11Mbps
- Omni=2dBi

And, I was investigating what this will be able to pick up if added to
the Lenovo X61t Linux Laptop:

Alfa Networks AWUS036H ($28)
- TX = 20dBm (100mW)
- RX = -91dBm@11Mbps 802.11b CCK
- Omni = 2dBi

Once I understand the equipment specifications I need, THEN I will
proceed to the calculations of what signals they can pick up. I am not
doing this theoretically - I'm only interested in real live signals that
I know are available to me such as what shows up in a site survey on my
outdoor WiFi equipment above or what the FCC coverage maps tell me for TV
(since I have no TV equipment as yet).

But, I figured I'd start simply with understanding what the capabilities
were of the equipment that I had on hand. For that, I simply needed to
figure out the specs.

I'm amazed that the dBi spec for the antenna on the Lenovo X61t is so
hard to find!

On Thu, 2 Feb 2012 00:43:42 +0000 (UTC), Chuck Banshee


If it's not already getting tossed around in the wind, that should do
it.