OSCAR-11 Report

[Clive Wallis <clivew@xxxxxxxxxxxx>]

                OSCAR-11 REPORT    15 May 1998

During the period 16-April to 15-May good signals have been  received
from the 145.826 MHz. beacon. Its been an uneventful time.

Telemetry  has  shown  that  the battery voltage has tended to rather
low, mostly around 13.5 volts, with  values  between  13.3  and  14.0
recorded.   No  explanations of the changed power supply currents (as
reported last month) have been received, therefore I will now  regard
these as the nominal values.

The internal temperatures have remained  fairly  constant  at  around
5C and 3C for battery and telemetry electronics respectively.

A  single  WOD  survey  of channels 1, 2, 3, 61 (magnetometers) dated
19-March-98 has been transmitted.  A quick plot of  this  WOD  showed
reasonable   agreement   with  the  theoretical  field,  and  nominal
attitude.  Anyone using this survey should note the unusual  starting
time of 16:00:05 UTC.

Three  reports  of the OSCAR-11 mode-S beacon have been received from
Fernando CX6DD, Gary  N4OLN,  and  Steve  HB9FMX/G4KAM.   Of  special
interest  is  the  equipment  used  by  CX6DD.  This  a modified MMDS
commercial TV antenna, model 130194,  made  by  California  Amplifier
Inc.   The device which is known as an LNBY, consists of a 23 element
antenna, 60 cm long, where each element is a  4.5  cm  disc,  and  an
integrated  down  converter which forms the remainder of the antenna.
There is sufficient space inside the unit to allow  a  cheap  surplus
HC-6  crystal  to  be  used,  instead  of the original HC-49 type.  A
8.8125 MHz.  crystal would give an IF in the 145 MHz.  band.  An ICOM
821H and FODTRACK software completed the system.  The audio file that
Fernando  sent,  showed excellent reception. The price of the antenna
(in Uruguay) was  US$190.   Further  details  can  be  found  on  the
California  Amplifier  web  site  -  www.calamp.com/  (Use the search
facility to find 130194)

The operating schedule is unchanged.

        ASCII status (210 seconds)
        ASCII bulletin  (60 seconds)
        BINARY SEU (30 seconds)
        ASCII TLM (90 seconds)
        ASCII WOD (120 seconds)
        ASCII bulletin (60 seconds)
        BINARY ENG (30 seconds)

The ASCII bulletin is currently a static message, detailing modes and
frequencies of all the amateur radio satellites.

There  are  additional  status  blocks  after  each bulletin is
transmitted, and between ASCII TLM and WOD.

The mode-S beacon is ON, transmitting  an  unmodulated  carrier,  but
telemetry indicates that it has partially failed, and delivering half
power.   This beacon is a useful test source for those testing mode-S
converters, prior to the launch of P3-D.  It is  considerably  weaker
than  DOVE,  which should be used for initial testing. Any reports of
reception  on  2401  MHz.   would  be  most  welcome.  Please  e-mail
g3cwv@amsat.org.

The 435.025 MHz. beacon is normally OFF.  However it can sometimes be
heard  when  the  satellite is being commanded by ground control, ie.
within range of Guildford, UK.  When the 435 beacon is  transmitting,
the  145  beacon  is  normally  OFF.   The data transmitted is mainly
binary.

        RECENT ADDITIONS TO WEB SITE

In response  to  many  requests  for  information  about  methods  of
decoding  OSCAR-11  signals,  I  have now added a package of hardware
information to my web site.

Another recent addition is a new page for miscellaneous  topics  such
as  tracking, eclipses, and orbital decay. The first addition to this
new page is a package for evaluating satellite eclipses, as described
in OSCAR News April 1998, page 29. The other item in this new page is
a program OZFORM.BAS for generating a  table  of  Keplerian  elements
from  the NASA 2-line format.  The format of the output is similar to
that published in every OSCAR News.

The web site also contains some  software  for  capturing  data,  and
decoding  ASCII  telemetry  and  WOD. There is an archive of raw data
(mainly WOD) for analysis, which is continually  being  expanded,  as
new  data  is captured.  Also included are some audio files, examples
of each type of data transmitted by  OSCAR-11,  each  one  plays  for
about ten seconds.  There are also examples of mode-S reception.  All
the  audio  files  are  zipped,  so that they can be played off-line.
These should help listeners identify the various types of  data,  and
give  an  indication  of  the  signal quality required for successful
decoding.

The URL is -

      http://www.users.zetnet.co.uk/clivew/

If you place this bulletin on a terrestrial  packet  network,  please
use the bulletin identifier $BID:U2RPT25.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org