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CX3VB > SAT 27.04.03 22:52l 165 Lines 6307 Bytes #999 (0) @ WW
BID : 12163-CX3VB
Read: GUEST
Subj: DECODING UO-11
Path: DB0ZKA<DB0GPP<DB0LX<DB0RBS<DB0SWR<DB0MW<DB0IDN<DB0AIS<DB0ROF<DB0ERF<
DB0FBB<DB0GOS<ON0AR<ON0AR<EB2BJX<ON0BEL<CX2ACB<CX2SA<CX3VB
Sent: 030427/2008Z @:CX3VB.CELA.URY.SA #:12163 [Melo] FBB7.00e $:12163-CX3VB
From: CX3VB@CX3VB.CELA.URY.SA
To : SAT@WW
DECODING OSCAR-11 SIGNALS WITH A SOUND CARD
During the last few years I have received many enquiries regarding
soundcard software for decoding OSCAR-11 signals, and from time to
time there has been some discussion on AMSAT-BB about the need for
this software.
I am pleased to say that a suitable Windows program for displaying
and capturing OSCAR-11 data is now available. This is MIXW2, a
general purpose Amateur Radio data communication program written by
Nick Fedoseev UT2UZ.
You can download the the program from www.mixw.net or do a google
search for MIXW. You need the latest version 2.07.
The OSCAR-11 feature is un-documented at present. You need the
following settings -
MODE RTTY
NOT inverted
MODE Settings
RX Frequency 1800
Baud Rate 1200
Shift 1200
Character set ASCII-7
NOT inverted
If these values are not shown as preset options, just enter the value
in the text box for the item.
Your receiver should be set to NBFM 145.826 MHz. +/- 3 KHz. Doppler.
MIXW should display ASCII text when the signal is fed into the sound
card line input. Alternatively the signal may also be recorded, and
played back into the sound card, at a later time. Useful for
testing. There are no special requirements for the audio recorder,
most types should be suitable.
To start capture of the text, click on File/RXlog/Open RXlog, enter
the file name you wish to use, and click on SAVE. Close to stop
capture. It is convenient to use a date code for each session
captured, eg 030217.log ( 2003, February, 17).
I have found that this program works very well on OSCAR-11, and gives
results comparable to a hardware decoder.
If you haven't used MIXW or any sound card applications before, you
may find that the line input needs enabling. A way of checking that
the sound card works is to record and playback an audio signal using
the Windows sound recorder/player. In Win98 this is located in -
Programs/accessories/entertainment/sound recorder. If it doesn't
work for the line input, check that this channel is enabled in -
programs/accessories/entertainment/volumecontrol/options/properties/recording
There is a useful moderated, free mailing list, for users of MIXW. For
details visit http://groups.yahoo.com. To join the list you will
need to register with the site, and be accepted by the moderator. To
avoid spam, the site has a high level of security.
On my website ( www.users.zetnet.co.uk/clivew ) there is a package
for decoding the telemetry, U2TM.ZIP. Normally this is used with a
hardware decoder, via the capture program CTERM. The format in the
RXLog file is not fully compatible with the output of CTERM. I have
therefore written a small conversion program FILTER_M which is
included in this package.
INSTRUCTIONS FOR FILTER_M.EXE
This is a Windows program, written in BBC BASIC for Windows. It
should run on all versions from Win 95 and above. Copy the
program into the directory containing the data files, this will
eliminate the need for entering the full path for each file. Click on
START/RUN and enter c:\u2tm\filter_m1.exe ( assuming the program is
located in c:\u2tm\ ).
Enter the input and output file names as requested. When the program
has finished, it will tell you how many bytes have been processed.
Close the program window in the usual way. The output data may then be
processed by U2TM or U2AWOD as required.
TECHNICAL DETAILS OF THE FILTER PROGRAM
The problem with the RXLOG.TXT file is that extra CR & LF characters
have been added to the data received from the satellite.
When the satellite sends 0d 0a, MIXW stores od 0d 0a. When the
satellite sends 0d 0a 0a, MIXW stores 0d 0d 0a 0d 0a. In both cases
the 8th bit has been removed before processing, ie received as 7 bit
ASCII. Also hex 1e is stored at the start of the frame, ie. the
line starting with 'UOSAT-2'.
I assume that the extra characters have been included to help format
the display. Hovever the display works OK, and does not need
changing.
The rules required for filtering and storage of data received from
the satellite are -
1. Remove 8th bit
2. Store ONLY hex codes 0a, 0d, 20 to 7c inclusive.
3. Do NOT store any characters NOT received from the satellite.
GENERAL COMMENTS
This package contains three sample RxLog files (file extension .LOG,
and their converted equivalents (file extension .RAW ). There is a
short telemetry file, a long telemetry file, which is a complete pass
of data recently captured. There is also a complete pass dated 1997,
when the diary cycle was in operation. This is captured from the
same audio tape used to prepare the examples of hardware decoding in
the package SAMPLE.ZIP which is on my website.
If you are using Windows XP, you may have problems in running the
software contained in U2TM.ZIP, however it does work OK in DOS and
Win9x.
Many thanks to Nick UT2UZ and Dennis UU9JDR for producing the program,
and also to Reinhard DJ1KM for initially recognising that the program
could be used for OSCAR-11.
I would appreciate any comments from users of this software
73
Clive G3CWV
Hitchin, North Hertfordshire, UK.
15 April 2003
http://www.users.zetnet.co.uk/clivew/
Greetings from Melo city.
73 de Joe (CX3VB)
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