GB70U: From Guernsey to space – and back again

GB70U will be the callsign of the special event station from Guernsey to celebrate the Platinum Jubilee.

Over the course of the Jubilee weekend (Friday 3 and Saturday 4 June), GB70U will be hosted and operated by members of the Guernsey Amateur Radio Society. Located on the grounds of the Beau Sejour leisure centre in St Peter Port Guernsey, GB70U will operate on many bands and modes that are available to radio amateurs worldwide and will provide a unique opportunity for visitors to experience amateur radio.

One especially fascinating aspect of GB70U will be that the operators will send and receive signals via an actual satellite in orbit.

The station by Keith GU6EFB with narrow and Wideband operating position (Image credit: Keith GU6EFB)

The Es-hail 2 QO-100 satellite, launched in 2018 on the back of a SpaceX Falcon 9 rocket, is a commercial satellite in geostationary orbit (just above the equator at 26° East). What makes QO-100 unique is that it is the first commercial satellite to carry equipment designed and designated specifically for amateur radio use. It allows any operator within the highlighted coverage area to send and receive a variety of signals, including voice and even video.

The coverage of the QO-100 satellite. Any amateur within the yellow area will be able to make contact with the GB70U station.

This means any amateur radio operator (with the right equipment and skills) can “make contact” with other amateurs on the other side of the world via satellite communications.

One station at GB70U will be using the Es-hail QO-100 satellite. The station will be operated by Keith GU6EFB and will operate on the narrow band and digital amateur TV (DATV) transponder.


How GB70U plans to use the QO-100 satellite

The QO-100 satellite carries a narrow band transponder (limited to a bandwidth of 2,700 Hz). In practice, this means approximately 50 simultaneous two-way carriers to serve 100 users. Radio amateurs are allowed to use any mode that does now exceed the bandwidth, meaning GB70U can use many of the modulation types that are used with any single side band (SSB) transceiver.

Satellite dish in use at GU6EFB QO-100 station (Image credit: Keith GU6EFB)

Here at GB70U we plan to use some of the various modes including SSB voice communication along with Slow Scan TV (SSTV) for the exchange of still images, morse code (CW) radio teletype (RTTY) and FT4 and FT8 digital modes.

You can listen to live transmissions from QO-100 without the need for any special equipment directly from your computer or device by using the WebSDR hosted at Goonhilly Earth Station in Cornwall.

There is also a separate, wideband transponder aboard QO-100 (with an available bandwidth of 8 MHz). This uses different frequencies and lower bit rates than commercial satellites, but extremely good results transmitting audio and video can be achieved. Take for instance this recording of the BATC net (a regular get-together “on the air), where likeminded radio amateurs share their thoughts using digital amateur television via the satellite.


At GB70U, we plan to transmit live Digital Amateur TV (DATV) using DVBS2 at 333ks at various time throughout the day.


Technical details

The narrowband transponder equipment in use will consist of the following: 

Transmission / Reception

  • ADALM-PLUTO Software Defined Radio – SDR
  • Amsat UK Filtered S Band Driver Amplifier
  • Amsat UK 5 watt 2.4 GHz amplifier

The output from the PA is fed via a short length of LDF4-50 coax to a Potty Patch dual band feed and a 1.2 metre offset dish.

On receive, a bullseye LNB with bias tee connected to the receive port on the Pluto.

All of the above is controlled by the SDR console software running on a Windows 11 i5 PC.

For use on the wideband DATV transponder the following equipment will be used for transmission:

  • BATC Portsdown Four transmit / receive system
  • USB camera
  • Lime mini SDR
  • Amsat UK Filtered S Band Driver Amplifier
  • PA surplus 2.4 GHz amplifier
  • Windows 11 i5 PC running OBS and F1EJP script for FFMPEG

The output from the PA is fed via a short length of LDF4-50 coax to a Potty Patch dual band feed and a 1.2 metre offset dish.

Reception

On Receive, a bullseye LNB with bias tee on the 1.2m offset dish will be used, together with a BATC MiniTioune receiver and BATC Ryde receiver.


Additional information

If you’re intrigued by satellite amateur radio, here are some useful links:

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