Re: ARISSAT1 TELEMENTRY


K6LCS <clintbrad4d@...>
 

Isn't that a 100mW transmission? And with a hardly-any-gain-at-all J-Pole .... Well, I wouldn't try that combination.

Here's the stuff from the ARISSat-1 page on receiving the telemetry - you probably already know this ...

How To Receive the ARISSat-1/KEDR BPSK-1000 Telemetry

The BPSK transmission from ARISSat-1/KEDR will feature a new 1kBPSK protocol developed by Phil Karn, KA9Q to be readable in low signal level conditions. The BPSK data will transmit satellite telemetry and data from the Kursk experiment.

You'll need to take a few steps to get your station set up to receive, decode, and display the BPSK-1000 telemetry data:

You need a 2 meter SSB receiver.

An audio patch cable between your receiver and computer's soundcard is required.

Download the ARISSatTLM ground station soundcard demodulator and display software. Windows and Mac versions are available.

http://www.arissattlm.org/

Follow the instructions in the ARISSatTLM Software Quick Start Guide to install the software.

http://www.amsat.org/amsat-new/images/fck_images/ARISSatTLM-QuickStart%281%29.pdf

The ARISSatTLM software can decode BPSK signals in two modes:

Playback and decode a recorded file (even if you do not have a 2 meter SSB receiver you can experiment with the software and test file to learn about telemetry decoding and display!)
Live, off-the-air capture


Playback and Decode a Recorded File

ARISSatTLM requires the recorded data to be in the WAV format. Compression formats such as MP3 are not suitable and will not decode and display correctly. Although .WAV files are notably large, usually several megabytes, they capture all of the bits of the signal. Compressed file formats sound OK to the human ear but save file space by eliminating bits from the recorded stream. You need to capture and record as many of the downlink bits as possible. An occasional noise burst or momentary fade is handled by the Forward Error Correction capability of the ARISSatTLM software.


Download the BPSK Test File

A link to a BPSK test file suitable for operation with the current release of ARISSatTLM software will be released soon to http://www.arissattlm.org.

NOTE: Some earlier BPSK test recordings that are on the internet will not work with the currently released software because they were created with earlier versions of the satellite's onboard software (the satellite software and ARISSatTLM are a "matched pair").

Start the ARISSatTLM program on your computer.

Click the start button in the lower left of the Tuning Indicator window.

In the ARISSatTLM Version 0.50 Window select: File --> Open WAVE file. Select the ARISSatTLM test file you previously downloaded.

The Tuning Indicator window will show the "CW Bump" at proper location (note the "Put CW signal here" indicator).

The Morse Code Decoder will decode and stream the CW message.

The ARISSatTLM Telemetry as Text window will decode and display data.

The ARISSatTLM window will display the received data as received.

The display will stop when the end of file is reached.


Live Off The Air Telemetry Capture and Display

The ARISSat-1 BPSK-1000 downlink is transmitted in SSB mode on 145.920 MHz. When the CW2 beacon on 145.919 MHz is active this indicates that the BPSK-1000 format is being transmitted. If the CW1 beacon on 145.939 MHz is active this indicates the backup of BPSK-400 format is being transmitted.

Transmitting at 100 mW, both BPSK rates include Forward Error Correction (FEC) and it is expected that modest quarter-wave antennas with low-loss coaxial cable will provide sufficient signal strength for decoding and display by the ARISSatTLM software.

BPSK-1000 sounds like a "shusssch" with a higher pitch than the 400 bps growl. It is difficult to tune by ear. The BPSK beacon is centered 1 kHz above the CW2 beacon so that the CW beacon sits in the lower spectral null of the BPSK signal, i.e., in a narrow spot where there's no BPSK signal power.

If you put your receiver in USB mode and tune the CW beacon so it comes out at an audio frequency of 500 Hz, this will automatically center the BPSK signal in a conventional SSB filter extending from 300-2700 Hz. The Tuning Indicator window helps you tune the signal correctly.

Follow the recommendations in the ARISSatTLM Quick Start Guide for tuning and decoding the BPSK telemetry data. Once you are tuned in correctly (and adjust for doppler shift) you will be able to decode the BPSK-1000 signal. You will also be able to copy the CW2 beacon text in the Morse Code Decoder window.

AMSAT needs your telemetry from ARISSat-1/KEDR. Since there are no "Whole Orbit Data" storage mechanisms onboard ARISSat-1/KEDR, your submissions are the only way for AMSAT to collect the spacecraft telemetry and KURSK experiment results.

The telemetry may be recorded using the FunCube dongle or SDR-IQ receivers. After decoding the recorded file ARISSat-1/KEDR and Kursk telemetry CSV files (in the ARISSatTLM folder) can be sent as an e-mail attachment to telemetry@arissattlm.org
If you are running ARISSatTLM and receiving the signal "live" from ARISSat-1/KEDR, please enable the telemetry forwarding option.

/end/

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