400 bps PSK P3 Data Demodulator PCB

Introduction
The Phase IIID satellite [launched 2000 Nov 16 and called OSCAR-40, failed early 2004] used a 400 bps PSK block-oriented format for engineering telemetry because a widespread ground station network was already in place from previous Phase III spacecraft missions.

The Amsat Oscar-10 and Amsat Oscar-13 (AO-13) satellites transmitted continuously at 400 bps using PSK. The information available was, most importantly, plaintext bulletins with up-to-date operational information. In addition there was full housekeeping telemetry giving transponder status, navigation, power and temperature data.

Update: 2018 Nov 15

The original "AO-10 Data Demodulator" was introduced in 1984, and featured in Ham Radio (US), Wireless World (GB), Radio Rivista (I) and elsewhere. Its function was to take the AO-10/ AO-13/ AO-21 satellites' beacon audio and output an RS232 or parallel digital stream to display software for the IBM, Acorn Risc, Atari, BBC, CBM64, Spectrum etc families of computers. About 800 MK I PCBs were sold.

Over the years I maintained a wish list of improvements based on my own observations, and feedback from users. When stocks of the MK I demodulator were finally exhausted in 1992, I embarked on a substantial redesign, now known as the Phase 3 Data Demodulator, which incorporates the entire list.

Features

• No set-ups; load and go. A TNC is not required.
• Audio Input 5mv to 5v pk-pk; selectable sensitivity.
• Carrier frequency 1200-2400 Hz, default 1584 Hz.
• Optional: variable tuning by 16 position hex rotary switch.
• Opto-isolated up/down tuning outputs (both polarities).
• Digital Phase-locked-loops, crystal controlled.
• LED bargraph array tuning indicator.
• LEDs for Carrier lock, 400 Hz clock lock and Block.
• Block sync detector (31 bits).
• Block is 514 bytes, i.e. includes 2 CRCC bytes.
• Linear audio processing and matched filter (correlation) detector.
• Output 1 : 1200 baud 8N1, RS232 levels (RXD,CTS,DSR,GND)
  2 : 8 bit parallel plus strobe, TTL, 20 way IDC connector
  3 : Regenerated T(+)CLK, 2v pk-pk.
• Power 8-18v DC, 60 ma.
• Standard 74HC and 4000 CMOS. No unusual parts.
• Board is 210 x 150 mm, 8.2" x 6.0", i.e. ISO A5 size. Top professional quality double sided, maximum copper ground plane, plated through, solder resist and yellow silk screen legend. Four 3.3 mm mounting holes. Full documentation.

It is a load-and-go design. There are absolutely no set-ups, no pots, no tune-ups. If you build the board properly it will work right-off; audio in, RS232 out. You don't need test equipment unless you want to explore its workings (or fault find). All you have to do is tune in the satellite beacon until the LEDs light properly. Auto-tuning keeps the radio on-tune thereafter.

Analogue to Digital Converter (ADC) Upgrade Kit. The ADC kit is provided with the fully built board.

AO-40 telemetry archive.

AO-13 telemetry archive.

400 bps PSK P3 Data Demodulator Prices:

 Made-up and tested board incl. ADC kit: £50 (UK, EU), £55 rest-of-world
 Bare PCB board & instructions:          £10 (UK, EU), £12 rest-of-world
   Prices include postage and packing. Methods of payment

   Stock Remaining as of date below:
     Made-up and tested board: 6 units
     Bare PCB board:           2 units

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Last updated: 2020 Jul 05