[Mark] had his eyes on the nice quadrifilar helical antenna used by the Vaisla R92 ... an RTL-SDR dongle he picked up solid signals from Iridium satellites. Want to score your own radiosonde ...

The antenna normally operates in a vertical configuration. It looks like it might be simple to make some version of this without anything exotic. Let us know if you try! Helical antennas aren’t ...