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The EASIEST sat - FO29 digitalker



Since the previous posts on working the FO29 digitalker, I have been
asked several questions on how to hear the FO-29 digitalker.  What
follows is sort of an evolving FAQ. Feel free to distribute this
document.  KF4FDJ - March 26, 1999

Fuji Oscar 29 is a small LEO (Low Earth Orbit), Japanese owned satellite
containing a digitalker, mode JA transponder, and 1200 baud packet
capabilities.  The mode JA transponder requires a SSB uplink signal on 2
meters, and transmits a downlink SSB signal on 70 centimeters.  Mode JA
is a full duplex mode.  You WILL hear your own downlink, in order to
compensate for doppler.  The satellite is also capable of mode JD,
(digital) at 1200 baud.

Q    Is Fuji Oscar 29 always in digitalker mode, and what is it?
A    The digitalker on FO-29 is a digital loop announcement, which makes
the same announcement over and over. You will hear a ylleeeoop (bird
sounding signal), followed by "This is JAS two."  The Japanese Space
Agency, JAS, plans to cycle digitalker, mode JA, and mode JD.  Check
announcements on the BB for a schedule.

Q    Do I need a multimode rig to hear the digitalker?
A    Since FO-29 transmits in FM mode while in digitalker, any receiver
capable of tuning the 70 cm ham band should be able to detect the
signal.

Q    Do I have to use a high gain antenna to hear the signal?
A    Since the digitalker concentrates the power budget of the satellite
to the FM transmitter, instead of spreading it across a mode JA
transponder, it is a very strong signal!  It is possible to hear the
satellite with a handheld scanner or transceiver, and a stock "rubber
ducky" antenna.  Most 70 cm base stations, or scanner listening posts,
with fixed antennas, should also be able to tune the signal.

Q    I've heard that a circularly polarized antenna is necessary to hear
FO-29.  Is this true?
A    While a circularly polarized antenna will help on mode JA, it is
not necessary with the digitalker. It REALLY is possible to copy the
signal with a handheld device and a "rubber duck" antenna.  We have been
successful with a Yaesu FT50R and a stock antenna.  You will need to
rotate the rig (and antenna) for the best orientation.  Experience shows
that horizontal polarization, with the axis of the antenna perpendicular
to the satellite gives the best reception.  Experiment!

Q    Where do I tune to hear the signal?
A    The transmit frequency is 435.910.  Of course, you will have to
compensate for doppler shift.  Just remember you will tune a little
higher in frequency as the satellite approaches your position, and a
little lower in frequency as it recedes.  You will always be tuning
higher in frequency when the satellite comes over the horizon. Make sure
you have your radio set to tune small increments, as increases and
decreases in doppler are gradual, and linear. 

Q    How long will I be able to hear the satellite on each pass?
A    Since FO-29 is a low earth orbit satellite, most passes will be
between 6 and 18 minutes in duration.  Timing is critical in working any
amateur satellite.

Q    What is the purpose of the digitalker?
A    The digitalker presents an easy opportunity for hams and non hams
to have their first taste of real time reception of signals from space. 
Use this opportunity to show a kid, or a terrestrial ham how easy it can
be to tune a satellite.  This opportunity is excellent for scout
meetings, monthly ham meetings, schools, or any place where inquisitive
persons congregate.  

Q    How will I know when the satellite is over my location?
A    You will need to have a program to give you predictions of when the
satellite is "visible" to you.  An excellent place to find downloadable
software for real time tracking of satellites, and other information on
the amateur satellite program in general, is:  http://amsat.org  Be sure
to download the latest keplarian coordinates for your tracking program. 
Each prediction program needs these coordinates to determine where the
satellites are, and to help you determine when FO-29 will be over your
horizon.
  
If you have any comments, additions, or modifications to this document,
please contact me directly.  We will attempt to post the latest version
whenever the satellite is toggled to digitalker mode.

73, Mike KF4FDJ

 
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