In article ,
Helmut Wabnig *_.-_- wrote:

On 22 Aug 2006 11:39:54 -0700, wrote:

Hi,

First off let me state that I'm a newbie in RF hardware so my apologies
if this is a dumb question. For an experiment I'm conducting I want to
be able to transmit two data streams from two WiFi(b) routers at the
same time. I realize that they have carrier sense avoidance so that if
they are right next to each other they will not transmit at the same
time. Is there a piece of hardware (filter, diode? or something?) that
i can put between the output of the routers and their respective
antennas such that this device will pass the transmit signal to the
antenna but not pass any radiation received from the antenna to the
routers? The idea then would be that the carrier sense would not come
into play as no power would be received from the antennas. Any ideas
or suggestions would be greatly appreciated. Thanks,

Kev
A circulator would do the trick.

http://www.ditom.com/microwave-circulator.htm

https://ewhdbks.mugu.navy.mil/circulat.htm

Rather expensive, sometimes to be found on Ebay.

w.

Why would there be a significant problem in the first place....
these aren't CW devices, they are Packetized Spread Spectrum
and two devices next to each other, even on the same channel, would
not run into each other, due to different spreading code roots
anyway..... Hmmmmm, non problem, from where I sit.....

You wrote:
In article ,
Helmut Wabnig *_.-_- wrote:

On 22 Aug 2006 11:39:54 -0700, wrote:

Hi,

First off let me state that I'm a newbie in RF hardware so my apologies
if this is a dumb question. For an experiment I'm conducting I want to
be able to transmit two data streams from two WiFi(b) routers at the
same time. I realize that they have carrier sense avoidance so that if
they are right next to each other they will not transmit at the same
time. Is there a piece of hardware (filter, diode? or something?) that
i can put between the output of the routers and their respective
antennas such that this device will pass the transmit signal to the
antenna but not pass any radiation received from the antenna to the
routers? The idea then would be that the carrier sense would not come
into play as no power would be received from the antennas. Any ideas
or suggestions would be greatly appreciated. Thanks,

Kev
A circulator would do the trick.

http://www.ditom.com/microwave-circulator.htm

https://ewhdbks.mugu.navy.mil/circulat.htm

Rather expensive, sometimes to be found on Ebay.

w.

Why would there be a significant problem in the first place....
these aren't CW devices, they are Packetized Spread Spectrum
and two devices next to each other, even on the same channel, would
not run into each other, due to different spreading code roots
anyway..... Hmmmmm, non problem, from where I sit.....

I'm running 802.11b @ 2.4Ghz. As I understand it at 11Mbps (which I'm
using) the signal is "spread" using the CCK code, and each packet/user
uses the same spreading function. So a transmission only goes forward
if the channel is "empty", i.e. the received power at the transmitter
is below some carrier sense threshold (dBm)......

On 22 Aug 2006 16:28:09 -0700, wrote:

Why would there be a significant problem in the first place....
these aren't CW devices, they are Packetized Spread Spectrum
and two devices next to each other, even on the same channel, would
not run into each other, due to different spreading code roots
anyway..... Hmmmmm, non problem, from where I sit.....

I'm running 802.11b @ 2.4Ghz. As I understand it at 11Mbps (which I'm
using) the signal is "spread" using the CCK code, and each packet/user
uses the same spreading function. So a transmission only goes forward
if the channel is "empty", i.e. the received power at the transmitter
is below some carrier sense threshold (dBm)......

Hi All,

Spread Spectrum is merely the 0 level of the protocol stack and has
nothing to do with "going forward." That is a software issue at a
much higher level that deals with packet collisions. The hardware may
augment collision detection through carrier sense (which would only
occur if both share the same code). In fact, thresholds may be well
below the noise floor (dBm) and still work with notably lower
throughput, but this is an even more remote issue, except you may be
fighting poor isolation from even the best of isolators.

73's
Richard Clark, KB7QHC