I put an RMY 05103 on my workbench connected to a calibrator. I'm turning the speed shaft at various speeds.
The H11A1 has a single led for DC input while the H11AA1 has dual leds for AC input. I didn't connect an optoisolator to the RMY 05103.
I haven't converted to MPH but at 3 wind (shaft) speeds, the generator output is #1 336mv @ 10HZ, #2 600mv @ 21HZ; and #3 highest speed 2.28 volts @ 86HZ. The generator produces three cycles per revolution (1RPM=3HZ)(1MPH=0.01096RPM)
This means that at very low wind speeds, the generator doesn't produce an output voltage high enough to drive the H11AA1 leds. Using an optoisolator, the wind measured threshold will be several MPH (no output) even with the impeller rotating.
I believe that I'll have to stick with my design using op-amps to amplify and square up the generator output. I'll get back to that old circuit soon.