Re: [amsat-bb] WiFi users "may" try AO-40, look out!

[Bob Bruninga <bruninga@xxxxxxxx>]

On Fri, 12 Apr 2002, Commander Data (KA9UCE) wrote:

> As I peruse the WLAN users forums, I found a rather disturbing scenario,
> and it involves a few folks thinking of making an attempt to access
> AO-40 using their 802.11b WiFi lan gear.

Rather than trying to tell them they are wrong and don't do that (it
rarely works), try re-directing their interest to our ICsat which our
students are working on which is a satellite using LAN cards as the link.
With a one watt amp, and our 40 foot dish, we hope to close the link to
the satellite on one of the channels in the HAM band.

To make this work, we need to determine two things:

1)  Are there any TIMING parameters in the implementation of 802.11b that
are time critical.  That is, the end-to-end turn around time will be on
the order of a millisecond instead of a microsecond.  WIll this affect
ack/nak timeouts, etc?

2)  Doppler.  The doppler is insignificant relative to bandwidth, but it
is changing.  Are the spread spectrum tracking loop filters  fast
enough (once locked on) to keep moving with changin doppler, or do
they try to absolutely lock in with a very long time constant.

We are spending an awful lot of time in building a dual mixer,
multi-isolator, multi-siggen table top system to find the maximum rate
of doppler possible..  but can think of no way to test the TIMING
delays...  Other than finding someone who konws every detail of the Cisco
card implementation...

de WB4APR


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