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This latest beacon operates as G0BWC on 144.021MHz, transmitting just 10 milliwatts every 10 seconds, using 4FSK "Horus Binary v2" modulation. This is decoded using the HorusGUI software, set for 50 baud and 244Hz tone spacing and the program will automatically calculate the distance, bearing (and elevation) from your receiver. There's also an experimental web-based decoder: https://horus.sondehub.org/
In addition to the 4FSK, the beacon also identifies using Morse (CW) after every ten packets.
Please use the form below to report your reception of the beacon.
Each telemetry frame (32 bytes) consists of the following elements:
Callsign, frame_number, time, latitude, longitude, altitude, speed, satellites, CPU_temp, CPU_voltage, then four null fields, checksum.
If the "Upload to Sondehub" box is ticked, it will automatically send the received packet to the Sondehub Amateur site, along with your received Signal-to-Noise Ratio and frequency (if you've entered your Radio Dial Freq, in the panel). Please don't enable this feature whilst we're testing on the ground (instead you could Enable Logging in the "Other" tab and save a local .CSV file).
This Horus Binary 4FSK mode has been popular on 70cm for High-Altitude Balloon flights in Australia and around continental Europe over recent years, but we believe that this is the first time it's ever been deployed on 2m.
Following up on the success of the low-power CW beacon built by Steve G4AQB, Ross G6GVI has been working on another 2m beacon transmitter, now incorporating a satellite receiver to include time and position in its message and using Frequency-Shift Keying to transmit the data at a faster rate.
The frequency reference is just a crystal, so it will drift over a few hundred Hertz as the temperature changes. The radio board is designed for use at 433MHz, so a custom low-pass filter (see below) is needed to reduce spurious harmonic emissions when operating at 144MHz.
The first prototype (based on an ESP32 micro) was assembled from left-over bits from other projects plus an atmospheric sensor to measure temperature, pressure and humidity. This version transmits alternating 2FSK (RTTY) and 4FSK (Horus Binary) formats at 100 bauds.
Later, this test-jig was adapted to run with an Arduino Pro Micro, now transmiting just its position via 4FSK, without any atmospheric sensor data.
Then finally the code was ported onto a lightweight miniature "TinyThing" board, for further testing: on the ground and ultimately in the air!
After rebuilding my low-pass filter on a smaller board (using SMD inductors), I've got the weight down to less than half an ounce.
Output spectrum of 433MHz unit operating on 2m
Output spectrum with low-pass filter fitted
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