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Re: WiFi users "may" try AO-40, look out!



On Fri, 19 Apr 2002, Phil Karn wrote:

> >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.
>
> The good news is that DBPSK at this speed would be essentially immune
> to Doppler. However, DBPSK without coding requires an Eb/No of about
> 11 dB for good performance, so at 1Mb/s you'd need a received S/No of
> about 71dB-Hz.  You'd need even more if the receiver is less than
> ideal. How much do you have? Have you tried to measure the S/No
> performance of any actual 802.11b cards?

Yes, the card was spec'ed at -94 dBm at the 1 megabit rate and after
measuring and calibrating with some good attenuators and spectum analyzer
we were surprised that in fact, we measured the knee in the error rate
within a fraction of a dB of that very point.

de WB4APR@amsat.org, Bob

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