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 the drawing: http://aprs.org/transit/call-encoding.GIF
Using the scenario below: Bob, Wb4APR > -----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) for > reception (downlink) via RF. > > We will use a 5 bit code (like RTTY) but will replace the CR and > LF with the "." and a CAPS shift. SO the 31 possible characters > are a-z plus "." plus CAPS, FIGS and LTRS. This allows normal > mixed case text... > > Bob, WB4APR _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
