From mboxrd@z Thu Jan  1 00:00:00 1970
From: Luis R. Rodriguez <lrodriguez@atheros.com>
Date: Wed, 18 Aug 2010 10:23:23 -0700
Subject: [ath9k-devel] AR9223 with 3 antennas
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References: <4C6BF1DB.8010107@dev2day.de>
Message-ID: <20100818172323.GD31593@tux>
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On Wed, Aug 18, 2010 at 07:44:43AM -0700, Jan Friedrich wrote:
> Hello Luis,

Please send these type of questions to the mailing list.

> At my working place (University of Leipzig, Germany) we use PCI-Cards
> with the AR9223 chip (D-Link DWA-547) that feature 3 antennas each. As
> far as I know the AR9223 is the same as the AR9220 but supports only
> 2.4GHz. And the AR9220 is somehow identical to the AR9280 which supports
> 2x2 MIMO.
> 
> My simple question: is the third antenna in any way used by the Atheros
> AR9223 or has there to be some vendor-specific circuit on the card that
> uses the third one? (There is no such thing as a datasheet for the
> AR9223 publicly available, isn't there?)

Its a 3x2 card, see the "Spatial Stream" section on this page:

http://wireless.kernel.org/en/developers/Documentation/ieee80211/802.11n#Spatial_streams

So for this card 3 antennas are available, two antennas are dedicated
to one chain with selection diversity.

  Luis