[amsat-bb] Re: New Satellite Downlink? (Drawing)
bruninga at usna.edu
Thu Aug 26 11:52:23 PDT 2010
Here is more info on how we could use the Navigation message of
these old satellites for a rudimentary satellite Q-Tweet system.
That is, you can send "Quarter-Tweets" for inclusion in the
downlink... But only after you have scheduled a login and
obtained (in the next downlink) your authorization code... See
Using the scenario below:
> -----Original Message-----
> On Behalf Of Robert Bruninga
> Sent: Thursday, August 26, 2010 8:39 AM
> Subject: [amsat-bb] Re: New Satellite Downlink?
>> Transits #23 and #25. object nos 19070 and 19419.
> Here is a possible application based on the unique
> nature of the "navigation" message which is 26 lines
> of 6 words with each being 39 bits. But one word in
> each of the first 8 lines are changed every 2 minutes
> by inserting a new word and scrolling off the oldest
> one. We can use this for a list of callsigns.
> We can get a callsign and extra 8 bit authorization
> ID into each of the 39 bit words. Then the rest of
> thos first 6 lines can be older callsigns and then
> the remaining 18 lines are available for what I call
> Quarter-Tweet messages of 35 bytes each. We will
> also reserve a few lines for special bulletins.
> So here is how it would work.
> 1) User initiates a login request via internet to
> the command station.
> 2) His call is added to the Login list on the
> satellite plus an authorization byte
> 3) As noted above, this list scrolls down and only
> the last 48 are visible
> 4) Next he has to tune in the downlink to see his
> authorization byte.
> 5) Now with his authorization byte, he can send a
> Q-tweet via the internet.
> 6) Which now shows up with 18 other Q-tweets in
> the remaining 18 lines downlink
> Your Qtweet can contain a call to another station and
> when he responds, you can count a QSO.
> Something like that. The above idea lets everyone play, but
> requires that they can hear the satllite first (like any other
> satelite) before then can send an uplink (via the internet)
> reception (downlink) via RF.
> We will use a 5 bit code (like RTTY) but will replace the CR
> LF with the "." and a CAPS shift. SO the 31 possible
> are a-z plus "." plus CAPS, FIGS and LTRS. This allows normal
> mixed case text...
> Bob, WB4APR
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