STARSHINE COMMUNICATIONS DESIGN DETAILS: STATIONS: This table shows the uplink power and receive antenna gains for all expected stations in the APRS Satellite system. Standby receive gain is for the user who is not aware of, nor optimized for satellite reception. For example, an HT in a pocket, or mobile parked under trees. ERP ERP Rcv Rcv Rcv UHF VHF UHF VHF STBY USERS (W) (W) dBi dBi dBi Applications --------- --- ---- --- --- --- ------------------------------ HANDHELDS 3 5 3 3 -6 Sailboats, Hikers, Wilderness MOBILES 70 100 5 5 -6 Boats, Remote Travelers HOME STNS 700 1000 13 13 Not intended for PCsat NETWORK IGATE RCV 7 5 Omni Internet receive site MSG NODE 70 100 Internet to user UPLINK site COMMAND 700 1000 13 13 USNA MISSION GOAL: Handheld and Mobile digital communications with Whips. 1) Handheld/Mobile message uplink to Internet (emergency and routine) 2) Handheld/Mobile message downlink delivery from Internet 3) Handheld/Mobile to Handheld/Mobile real-time digital comms 4) Nationwide Bulletin delivery to all users 5) Handheld/Mobile GPS position tracking to internet 6) GPS tracking of buoys, telemetry devices, wildlife, spies 7) Other UI digipeating applications (TBD) BOUNDARY CONDITIONS Driving Starshine ooperations on 2 meter band: 1) Optimum ALOHA CSMA channel effeciency is about 20% due to collisions 2) VHF links have a 9 dB advantage over UHF links (omni to omni) 3) 1200 baud AFSK has a 7 dB advantage (measured) over 9600 baud FSK 4) T/R delays render 9600 only twice as fast as 1200 for short bursts 5) UHF uplinks require wide bandwith to avoid doppler (- 4 dB) 6) UHF downlinks require user tuning throughout pass (not desired) 7) Commercial amateur radio Handheld and Mobile all-in-one digital transceviers are now readily availaable (Kenwood and Alinco) REQUIREMENTS/CONSTRAINTS Design Drivers: The following constraints were used to arrive at the optimum hardware/operational configuration: 1) MSG delivery to HT in Standby requires best possible downlink (1200 baud VHF). Igate uplink is relatively unconstrained. 2) MSG receipt from HT requires best possible uplink (1200 baud VHF). Downlink to internet is relatively unconstrained. 3) Continent wide Bulletin Delivery requires existing 144.39 (1200 baud) 4) HT/Mobile real-time messaging requires same up/downlink baudrate 5) GPS HT/Mobile tracking is relatively unconstrained. 6) Low power GPS tracking devices requires best uplink (1200 baud VHF) and the uplink must not be used by any other satellite uplink to avoid unintentional interference to other systems. 7) Other UI digipeating applications should be crossband full duplex and should use same up/downlink baud rates 8) Store-n-forward is relatively unconstrained with equal baud rates 9) Spread of applications among multiple receivers to minimize collisions is desired. 10) Synchronizing of downlink transmissions is desired to maximize the available half-duplex satellite receive time. 11) Reundancy and Backups are desired. 12) UHF downlinks are of little value due to poor link budget and doppler 13) UHF Uplinks without Doppler tuning is possible with a 30 Khz Sat Rcvr 14) KISS Principle should reign. (Keep it Simple, Stupid) HARDWARE: Starshine could consist only of one KPC-9612 dual port TNC that can gate packets between either port. Since we only have one transmitter on VHF for best downlink, we can output both the 1200 and 9600 baud channels to the same transmittters shown below. We can make them in eitehr single or dual channel models: STARSHINE 145.825 ------> 1200 Baud -*-----> 145.825 GPS--/ \ / | / \ | 435.250 ------> 9600 Baud -* STARSHINE 145.825 ------> 1200 Baud -*-----> 145.825 TRANSMITTER SCHEDULING: To maximize receive (uplink) time, a cycle timer is used to drive the channel-busy input of the TNC. By holding off the transmitter until several packets are buffered up, then the individual TX Delays are amortized into only one TXD to help optimize receive time... Bob Bruninga, WB4APR