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Home.md

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-Welcome to the horusdemodlib wiki!
+# Project Horus's Telemetry Demodulator Library
+
+![Horus Binary Modem FFT](https://github.com/projecthorus/horusdemodlib/raw/master/doc/modem_fft.jpg)
+Above: Spectrogram of the Horus Binary 4-FSK modem signal.
+
+## What is it?
+This repository contains:
+* libhorus - A C library containing a high performance 2/4-FSK-demodulator (originally developed as part of the [Codec2](https://github.com/drowe67/codec2) project by [David Rowe](http://rowetel.com)), along with Golay and LDPC forward-error correction algorithms.
+* horus_demod - A command-line version of the FSK demodulator.
+* horusdemodlib - A Python library which wraps libhorus, and provides additional functions to decode telemetry into formats suitable for uploading to the [Habhub tracker](http://tracker.habhub.org) and other services.
+
+In particular, this library provides a decoder for the 'Horus Binary' telemetry system, which is the primary tracking system used in [Project Horus's](https://www.areg.org.au/archives/category/activities/project-horus) High-Altitude Balloon launches.
+
+The modem in this library can also decode the standard UKHAS RTTY telemetry used on many other high-altitude balloon flights.
+
+## Why use it?
+A HAB telemetry payload transmitting Horus Binary format telemetry can provide position updates approximately every 3 seconds. Using just 10mW transmit power on the 434 MHz [ISM](https://en.wikipedia.org/wiki/ISM_band)/[LIPD](https://www.acma.gov.au/licences/low-interference-potential-devices-lipd-class-licence)/70cm band, this modem can offer ~7dB improved demodulation performance compared to [RTTY](https://en.wikipedia.org/wiki/Radioteletype) running at the same baud rate. There is some further information on the modem performance [available here](https://www.rowetel.com/?p=5906).
+
+This means potentially longer decoding range, both in the air, and on the ground. The modem uses rate [Golay(23,12)](https://en.wikipedia.org/wiki/Binary_Golay_code) forward-error correction, so you'll have far less issues with failed packet decodes.
+
+The ye-olde RTTY transmitters used by many high-altitude balloon flights encode telemetry as ASCII text. This is very wasteful compared to just sending data as raw binary types. RTTY also uses [RS232](https://en.wikipedia.org/wiki/RS-232) framing, which means even more overhead. Horus Binary uses a binary packet format, which gets the basic tracking data across in just 22 bytes. Information on the packet and framing format is [available here](https://github.com/projecthorus/horusdemodlib/wiki/2---Modem-Details).
+
+The current Horus Binary modem uses ~1kHz of bandwidth, so can be received using conventional single-sideband receivers, just like you would do with a RTTY payload. Software-Defined Radio receivers can also be used.
+
+## How do I receive it?
+So, you want to receive telemetry from someone's high-altitude balloon flight, or set up to receive telemetry from your own payload?
+
+First up, you will need some kind of receiver for whatever frequency the telemetry is being transmitted on. Usually this is within the 434 MHz ISM/LIPD/70cm band, but could be different. 
+You need a receiver capable of receiving [Single-Sideband](https://en.wikipedia.org/wiki/Single-sideband_modulation), in particular the 'upper' sideband ('USB' - no, not that [USB](https://en.wikipedia.org/wiki/Universal_serial_bus)). 
+This could be a conventional amateur radio transceiver (think IC-7000, IC-706, FT-817, the list goes on and on...), or a scanner (Icom IC-R10, Yupiteru MVT-7100, etc...).
+
+You can also use software-defined radio receivers, such as the ubiquitous [RTL-SDR](https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/) (amongst others), along with software such as [SDR-Console](https://www.sdr-radio.com/console), [SDR#](https://airspy.com/download/), or [GQRX](http://gqrx.dk/).
+
+### Windows / Linux / OSX
+It's easiest to demodulate telemetry using Horus-GUI. [Use this setup guide.](https://github.com/projecthorus/horusdemodlib/wiki/1.1-Horus-GUI-Reception-Guide-(Windows-Linux-OSX))
+
+### Raspberry Pi 'Headless' Setup
+It's also possible to make a 'headless' (no screen) receiver using a RTL-SDR and a Raspberry Pi (or some other small Linux machine). Follow [this guide](https://github.com/projecthorus/horusdemodlib/wiki/1.2--Raspberry-Pi-'Headless'-RX-Guide).
+
+## General Info
+There is also some general information about running the modem from the command-line [available here](https://github.com/projecthorus/horusdemodlib/wiki/2---Modem-Details#usage---horus-demod).
+
+## How do I transmit it?
+Currently the 'reference platform' for Horus Binary telemetry transmission is the Vaisala RS41 radiosonde. Using [radiosonde_auto_rx](https://github.com/projecthorus/radiosonde_auto_rx) we track and recover these radiosonde and reprogram them with [our own open source firmware](https://github.com/darksidelemm/RS41HUP), which generates the Horus Binary modulation. 
+These radiosondes are launched in many places around the world, so go hunting and get your own free balloon tracker!
+
+**If you are going to fly your own payload using Horus Binary, you must get a payload ID allocated for your use. This can be done by submitting an issue or a pull request to this repository, or e-mailing me at vk5qi (at) rfhead.net**
+
+You will also need to set up a [Habitat Payload Document](https://github.com/projecthorus/horusdemodlib/wiki/5-Setting-up-a-Habitat-Payload-Document), so that the payload telemetry appears on the tracker.
+
+There is also some older code targeting an ATMega328 + Radiometrix MTX2 [available here](https://github.com/darksidelemm/uAvaNutBinary/tree/master/uAvaNutBinary), however this code has not been used in a long time. 
+
+I intend to produce implementations for other common transmitters, such as the RFM98W, which should also be capable of much higher order MFSK modulations, improving performance even more!
+
+## Contacts
+* [Mark Jessop](https://github.com/darksidelemm) - vk5qi@rfhead.net