Communication System

One of Starshine 3 primary objectives is to involve more school children in
radio science.  As part of this mission, science data from experimental
solar cells mounted on the surface of the satellite will be downlinked in a
manner that will allow schools and radio amateurs to participate in
collecting the data.

For this reason, the downlink has been designed for compatibility with
standard amateur satellite radio ground stations.   It is also compatible
with Kenwood THD-7 hand-held radio terminals.  The THD-7 radios contain
built-in AX.25 Terminal Node Controllers (TNCs) and RS-232 ports.
Consequently, you can receive Starshine 3 downlink signals directly, for
recording on a standard laptop or desktop computer.  Schools that purchase
THD-7 or similar radios will be able to receive the Starshine 3 signals
with their identifying "STRSHN3  N7YTK" data header very simply.   We ask
that you forward your received packets as soon as possible  to a special
radio data collection web site that has been created for us by Michael
Tolchard at 

The Starshine 3 Communications System downlink uses 9600 bps
Frequency-Shift Keyed (FSK) signals at 145.825 MHz.  Downlink transmissions
will initially occur at two-minute intervals.  (The interval will be
shortened to every thirty seconds, if the surface-mounted solar cells
charge the on-board batteries satisfactorily.)  The Starshine 3
Communication System parameters are given below in Table I.

Table I:
Starshine 3 Communications System Parameters

Characteristic					Type/Value

1.  Center Frequency			145.825 MHz

2.  Data Rate					9600 bps

3.  Modulation					Narrowband FSK

4.  Deviation					+/- 3 KHz

5.  Baseband encoding			Differentially-encoded Non-Return to Zero (NRZI)

6.  Scrambling					G3RUH

7.  Protocol					AX.25 packet radio  -- APRS packet compatible.

8.  Uplink/Downlink Multiplexing:		Half Duplex

9.  RF Transmit Power			1.25 watts from RF power amplifier

10.  One suggested receiver		Kenwood THD-7

11.  Antenna                    Pair of quarter-wave monopoles fed 180 degrees
								out of phase

The Starshine 3 transmitter was derived from the SEDSAT-1 Mode L
Transponder, which has been operating on orbit since 1998.  Both systems
were designed and built by Cynetics Corporation.  The data collection
system was built by the South Dakota School of Mines and Technology.  The
antenna was built by the Physical Science Laboratory of New Mexico State