ARISSat How To: Operating Tips, Pointers, Downloads

From AMSAT-NA website:

ARISSat How To: Operating Tips, Pointers, Downloads

Radio-to-Soundcard Interface For Access to ARISSat-1/KEDR Bandwidth

(Thank you to Christophe Mercier, ARISS-Europe for the French translation of the ARISSat-1/KEDR description, ARISSatTLM Software Guide, Color Frequency Guide.)

The ARISSat-1/KEDR FM downlink on 145.950 MHz will be audible on all common 2 meter amateur radio receivers with no modification needed to your equipment. A CW/SSB receiver will also receive the CW beacons on 145.919 MHz or 145.939 MHz and the signals on the linear transponder passband between 145.922 to 145.938 MHz.

You can see the relationship of all of the ARISSat-1/KEDR frequencies with this color frequency guide.

To take advantage of the full bandwidth of the downlink for SSTV, CW Decoding, BPSK Decoding you’ll need to add a few things:

You’ll need an audio patch cable from your receiver to your computer soundcard audio input. If you are already on the air with other amateur radio soundcard applications then you are ready with the hardware to receive, decode, and display the SSTV, BPSK-1000 or BPSK-400 downlinks.
You’ll need SSTV software (refer to the SSTV news item)
You’ll need the ARISSatTLM software to decode the BPSK telemetry.

The key difference is that the SSTV signal is transmitted on the FM downlink on 145.950 MHz. The BPSK-1000 downlink is transmitted in SSB mode on 145.920 MHz. Depending on your equipment you may need to fabricate an audio patch to the computer soundcard input from both your 2 meter FM radio and 2 meter SSB radio.

An initial RECEIVE ONLY configuration is easily done consisting of an audio patch cable between your radio and the soundcard. The ARISSat-1/KEDR team testing the software noted that a minimal set up consisting of an audio cable from the speaker or headphone output from the radio to the line (or mic) input on your PC sound card was successful. If your rig has a ‘Line Out’ audio connection this can be run to the soundcard ‘Line In’ connection.

Many amateur radio “digital modes” articles, web pages, and books also discuss the more complex requirements to interface your transmitter to the soundcard and to control the push-to-talk functions. This is NOT required for you to successfully receive, decode, and display the signals you receive from ARISSat-1/KEDR. To join into the all the fun your RECEIVE ONLY configuration will just need the audio cable!
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.
Follow the instructions in the ARISSatTLM Software Quick Start Guide to install the software.

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.
The latest telemetry can be seen LIVE on your computer or cell phone.

How To Receive the ARISSat-1/KEDR SSTV Signal

The ARISSat-1 FM downlink on 145.950 MHz includes live SSTV images as part of the cycling voice ID, select spoken telemetry values, and the international greeting messages. Here are some pointers to help you get your station ready to receive and display the SSTV pictures transmitted by ARISSat-1.

One fun feature is that there are four SSTV cameras mounted on the spacecraft. On photos of ARISSat-1 you may have noticed black brackets on the outside of the spacecraft. These hold the mirrors that reflect the light onto the lens of the cameras. The software-defined-transponder will use the image data from the cameras to generate the SSTV downlink.

ARISSat’s software will sequentially select a new or stored image from one the four cameras. There are two pre-recorded images as part of the sequence. The camera that took the the picture can be identified by the color of the call sign in the upper left of the SSTV image. The SSTV image will be sent down as FM audio SSTV in Robot 36 format on 145.950 MHz about every 140 seconds.

The RF downlink power on the 145.950 MHz FM downlink will be 250mW which is predicted to provide a link margin around 6 dB on an HT with a ‘big whip’ when the satellite is at 15 degrees elevation. This should be sufficient to receive SSTV pictures although you may need to orient the whip to line up the antenna polarization.

ARISSat-1 is not stabilized so the antenna orientation is unpredictable and a certain amount of fading will happen. The receiving link margin may be improved with a handheld beam such as a commercially available “Arrow”, “Elk” antenna., The WA5VJB “Cheap Yagi” antenna web pages document how you can build your own.

See the news bulletin regarding tips and pointers for the audio interface between your radio and your computer’s sound card. When running your SSTV software just adjust the sound card audio gain slider and/or radio volume control so that the SSTV signal is within the center part of the bar. MMSSTV will give you an “overflow” indication if the volume is too high.

SSTV Software Download Sites

There are many amateur radio SSTV software decoding applications available. One of the easiest to use on Windows computers is the MMSSTV program.
The Ham Radio Deluxe software package also includes SSTV operation.
MultiScan SSTV software for the Mac.

If you successfully receive the SSTV transmissions, you are invited to upload your picture to to the ARISS SSTV Gallery.

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