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[Ham-80211] Activity - comments and idea

David Josephson dlj at bach.altaphon.com
Tue Jan 29 23:09:02 UTC 2008


Naber, Benjamin L. SPC wrote:
>  
> I've been working on a project, just a draft right now, but will be manifesting into the real deal in a little while. I would like to know everyone experiences with different multi-level modulations like QPSK, 8-PSK and the others that are being used. I like the QPSK or 8-PSK as that is what we use for our satellite internet. 
>   
Experiences are one thing, actual parts availability and 
bang-for-the-buck might be different. QPSK and 8PSK work great, and 
gives a pretty good tradeoff between power and bandwidth requirements. 
You will probably end up using off-the-shelf 802.11 chipsets, just 
because they work so well and are ubiquitous. The collection of 
modulation modes in 802.11 a and g (BSPK, QPSK, 16QAM and 64QAM) offer a 
good set of options to choose from. The challenge is getting deep enough 
into the chipset to use the modem directly without having legal access 
to the chip maker's proprietary code.

Historically, 64QAM was what the telephone company settled on as the 
best compromise for long distance microwave hops. Your MILSATCOM stuff 
is mostly 32QAM although some systems go higher. Only if you're really 
short on power, and have excess bandwidth (or very low data rate 
requirements) would you want to choose PSK.
>  
> What I'm working on is a TCP/IP setup that will have the functionality of a wireless router, but will have the functions amateurs like to see, and also be open source Linux so we can attract more computer people in here. Seeing how this a group with people who are computer oriented, there shouldn't be anyone griping "this is ham radio!" If you are one of them, then pay no mind as I pass you by.
>  
> If you are familiar with DD-WRT, it may have that setup as I like using that on my linksys and Motorola WRTs.
That (and its cousins in the open and mostly-open source community) is a 
good start. The snag has always been the hardware abstraction layer that 
the chipsets need.
> the main thing I like about this idea is that it will NOT require drivers on a computer to work so an old Toshiba Satellite 75MHz Laptop with an PCMCIA Ethernet port and TCP/IP support with Win3.1 will work.
>   
That's a good start. But it has to be cheap, too.

73 de WA6NMF




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