[Namaste-dev] DVB-S downlink format

William Blair wbblair3 at yahoo.com
Mon Jul 14 07:54:09 PDT 2008

I don't recall seeing a direct response to this suggestion.  Perhaps, I missed it?  Specifically, I like the low-cost, receive-only earth station using COTS hardware portion of the suggestion:

> Date: Tue, 1 Jul 2008 14:39:51 -0500
> From: "Howie DeFelice" <howie at aosusa.com>
> I couldn't agree more with Bob's assessment of the
> uplink. Giving the transponder a channelized appearance will
> certainly make operation easier to understand and use. Since the 
> receivers are SDR, there is no reason channel bandwidths couldn't be
> changed individually so that high performance class ground stations > had access to a larger variety of bandwidths (channels) than lower
> performance earth stations. 
> Along those lines, I was thinking there might be a benefit
> to adopt a standard DVB-S downlink format, mapping channels 
> into PIDs in the downstream frame. The largest single benefit of
> this is that it allows beginners to assemble a receive only earth
> station using very low cost parts; i.e. PCI bus DVB receive card
> (under $100), C-band LNB (under $50), small antenna (under $50).

> What would be needed is the magic software that pulls the data out
> of the PIDs and sends them to the appropriate codec or socket. I 
> did a link budget based on a 2Mbps downlink using 3/4 rate viterbi
> with 188/204 Reed Solomom, QPSK modulation and the link closed into
> a .6 meter antenna. I used some of the worst case parameters
> discussed on the message board.  When I needed to estimate
> parameters, I used typical Intelsat specs for global beam
> edge of coverage.
> OK, I know that build-it-yourself ground stations was not part of 
> the design criteria, but I thought it was worth putting out there
> for discussion...
> Howie
> AB2S


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