Current approach
As DVB-T is potentially problematic in regard of doppler shift, we want to use DVB-S. That makes the use of COTS parts difficult, as DVB-S modulators are not available in small sizes and are more expensive. With the availability of the LimeSDR Mini we have a cheap option of a radio module and can use a Raspberry Pi 3 for the creation of the bitstream. For now we will use only one-way communication.
The solution will be using a 5V power-rail (should be attached directly to the Raspberry Pi 3). At this moment we did not decide on a particular frequency (e.g. 900MHz or 1.2GHz band), so we do not have a specific PA yet. On the ground we will use a LimeSDR or a BladeRF to receive the signals.
As a sideproject we might have a intra-Rocket communication using BT and a extra-Rocket communication using WiFi (e.g. on the Launchpad). The Video Downlink System should be regarded as a potential fallback telemetry downlink system.
https://github.com/PiSupply/PiJuice
Old
Overview
In an effort to improve the video capture system we're attempting to implement the system developed by Alex Csete at Copenhagen Suborbitals. Charlie G got in contact with Alex regarding his original design. The software repo for the encoder can be found here. The video overview of the system can be found here. The system notably required a custom amplifier designed by Copenhagen Suborbitals. It was a two amplifier system designed by Peter Mortensen. The primary amplifier was based on the kit here, however the output power of the HackRF was too low, so an additional amplifier was added to the circuit, and a custom PCB created to minimize the connections.
This architecture implements the COTS DVB-S2 standard for high definition digital video and transmits in the 23cm band (1.3 GHz). Copenhagen Suborbitals saw a very stable link at 3.5W RF at 7 km altitude. Rocket Team believes we have an opportunity to simplify this system by integrating additional COTS hardware.
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Idea
From a discussion between Charlie and Dennis.
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- 3x Raspberry Pi 0 with camera (beware, need special camera cable: https://www.adafruit.com/product/3157)
- HV330 without PA (or with PA?)
- PA (needs to be a PA which supports wide bandwidth and digital modes. CW/SSB PAs are problematic)
- Antenna
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| Device | Input voltage | Power usage | Usecase | Size | Weight |
|---|---|---|---|---|---|
| Raspi Zero | 5V | 240mA Source, 350mA max | Video recording (with camera) | PCB: W(65mm) x D(30mm) | |
| HV-330-A / B | 12V | 300 mA@12V without PA | Encoding, Modulating, Transmitting | PCB: W(42mm) X D(42mm), stacked | PCB: 25g, with PA,Fan,etc: 70g |
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https://www.oe7forum.at/download/file.php?id=2035
Other implementations
In an effort to improve the video capture system we're attempting to implement the system developed by Alex Csete at Copenhagen Suborbitals. Charlie G got in contact with Alex regarding his original design. The software repo for the encoder can be found here. The video overview of the system can be found here. The system notably required a custom amplifier designed by Copenhagen Suborbitals. It was a two amplifier system designed by Peter Mortensen. The primary amplifier was based on the kit here, however the output power of the HackRF was too low, so an additional amplifier was added to the circuit, and a custom PCB created to minimize the connections.
This architecture implements the COTS DVB-S2 standard for high definition digital video and transmits in the 23cm band (1.3 GHz). Copenhagen Suborbitals saw a very stable link at 3.5W RF at 7 km altitude. Rocket Team believes we have an opportunity to simplify this system by integrating additional COTS hardware.