a while ago James Miller G3RUH published some nice articles about 2.4 GHz antennas used for OSCAR-13 and OSCAR-40 S-Band downlink. Indeed, such antenna will also work extremely well for QO-100 Uplink.
Gain is about 20 dBi RHCP, a 3dB beamwidth of 18°
I have one of those and it would actually make a nice portable antenna for QO-100, Uplink. indeed with the Converter removed (or replaced by a PA).