[ltp] External wifi antenna on t40?

[James P. K. Gilb]

Most of the mini-PCI cards in laptops use diversity (i.e. two antennas). 
  The antennas are usually attached via a small co-ax cable with push-on 
connectors (which I believe are standard sizes in most cases).

You could try to tap into one of the antenna connectors on the mini-PCI 
card, but you would have to either always have an external antenna 
attached or you would need to patch in a connector that breaks the other 
connection when you plug in your external antenna (this is what they do 
on PCMCIA cards that have external antenna jacks).  You don't want to 
attach two antennas to the same input without at switch, that would 
likely hose your performance.

With two antennas, hopefully the diversity algorithm will pick the 
better one, but you may find that it only TXs out of one of the two 
antennas, in which case you will want to attach your external antenna to 
that connector.

This assumes that they don't have a dedicated RX and TX antennas (I know 
of at least one chipset that was going to use this).  In that case, you 
would need two external antennas.

Since this is a T40, I would assume that surgery on the case is not a 
good idea.  I would suggest a PCMCIA card that takes an external antenna 
when you need the extra range or directivity.

BTW: It is possible that you will violate FCC regulations by attaching 
an external antenna that was not approved by the manufacturer, most 
likely by increasing the out-of-band emissions (there is plenty of room 
within the regulations for in-band power, the US allows up to 1 W with 
up to 6 dBi antenna gain, i.e. 4 W EIRP, while a typical 802.11 card 
transmits between 25 and 50 mW).

James Gilb

Alexander Gran wrote:
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> Am Mittwoch, 3. September 2003 03:38 schrieb Steve K:
> 
>>Anyone know if there is a place to hook up an external wifi antenna on a
>>Thinkpad t40?
> 
> 
> AFAIK no, as it has already one built in. But have a look in the hardware 
> manual (it's at ibm's website). They describe how to attach the builtin 
> antenna, so you could attach an other one, probaply.
> 
> Alex
> 
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