I had two QSO's on AO-51 mode L/S this morning on the 1310 UTC pass. I normally use a 1.2 meter dish for the mode S downlink antenna with a DEM downconverter.

On this pass I tested a 52 turn helix with an AIDC-3731 downconverter. Receiver performance was very good with consistent S7 to S9 signal strength and full quieting of the FT-736R for all of the pass except at low elevations at AOS and LOS.

This performance tends to confirm my direct comparison measurements and dissagrees with statements made in ARRL publications and expressed elswhere that the gain of helix antennas flattens out above about 20 turns.

Clare VE3NPC