Communicating with an amateur radio repeater in geosynchronous orbit, up until recently, remained a dream for most amateur radio enthusiasts, but that all changed when Qatar launched the Es’hail-2 (AKA QO-100) satellite last year. The satellite is designed to provide direct-to-home television services in the Middle East and North Africa region but also provides a linear transponder with an uplink on 2.4GHz (S-band) and downlink on 10.45GHz (X-band) for amateur radio enthusiasts, or others who are interested in satellite communication.
To communicate with the QO-100 in low-earth orbit, UK-based Tech Minds has built a dual-feed helix antenna that takes advantage of the satellite’s uplink and downlink, which includes a large dish for the S-band and a low-noise block downconverter (LNB) and feed horn. On the uplink end, Tech Minds used a helical design that features three and a half turns of heavy copper wire, along with a tuning section of copper lashing that connects to an N-type connector.
The downlink portion of the antenna has a Bullseye LNB situated in the center of an aluminum reflector disk, plus a cone-shaped radome (to keep it safe from the elements) and uses a series of 3D printed parts to tie everything together. Tech Minds’ dual feed helix antenna is an ingenious design, but unfortunately, the QO-100 is currently below the horizon, which means HAM radio enthusiasts in the US and East Asia won’t be able to establish communications. That said, Tech Minds did manage to establish both uplink and downlink with excellent signal strength, which should be repeatable for those within the satellite’s orbital path.