bi241@scn.org wrote:
> i played with the linksys WRT54G for a while and somehow got stuck in
> DD-WRT concept of diversity antenna. and also i am skeptical about the
> MIMO title that the Ralink chipset is advertised, after all, the
> AWLL5025 is still within 802.11G specs, while MIMO seems to belong to
> draft-N or whatever...
>
> but yeah in true MIMO design, diversity mean multiple RX antennas, (and
> mulltiple TX antennas too)
> i often see draft-N wireless adpaters with three antennas, just like
> the 802.11G AWLH5025 PCI adapter, but i was too lazy to learn about the
> antenna configurations. let me give it a try. these are possible
> configuration in a three-antenna setup
>
> a) three TX/RX combos
> b) one dedicated RX and two TX/RX combos
> c) one dedicated TX and two TX/RX combos
> d) two dedicated RX and one TX/RX combos
> e) two dedicated TX and one TX/RX combos
>
> i am still clueless about how many radios needed for one "draft-N"
> adaptor. but i do hope that there's no final N. 802.11 B/G is good
> enough for me, and for all, that's all we need for wireless
> internet.... as for networking, i'd prefer and recommend the old
> fashion way...
>
> anyways, in the case of the AWLL5025 USB, the external antenna must be
> the combo TX/RX. Thank you for pointing that out. it makes alot of
> sense... and i think i am gonna hack the antenna after this... yes i am
> serious!
>
>
> cheers

Diversity as receive only has been around for some time. Military of
course, but some high end automobiles had diversity receivers for their
FM broadcast reception.

I can understand diversity receive. The receiver comes up with some
sort of figure of merit on the reception. It is multiple transmit
(output) that confuses me. I don't see how a transmitter decides which
antenna to use. In any event, if everyone had diversity in the receive
path, I don't see why it would be needed in the transmitter.

http://www.smc.com/index.cfm?event=v...&scid=&pid=346
SMC2532W-B
is the high power card I use in my notebook. It has diversity receive,
but one transmitter. They claim half a mile on the detachable antenna.
Hardly. However, I've done drive-bys of at least a mile with the
biquad. Make that the bad biquad, i.e. the two wire instead of the
coaxial feed. I haven't tried the good biquad over any distance yet.

This is what Jeff considers the good biquad:
http://martybugs.net/wireless/biquad/

I used something like this for the feed:
http://www.hyperlinktech.com/web/con...p?SKU=AXA-NFNF

Typically they are smooth, not knurled. [Should be about a dollar at
the ham flea market.] Hacksaw one end off, leaving the center pin
exposed. Then position the adapter so you get the right distance
between the antenna and reflector. I cut the copper plate, drilled the
hole, then tinned the area around the hole with solder. This made it
easier to solder the N adapter to the copper plate. You need a propane
torch. [Benzomatic]




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