OK, sorry for the slow response, but I had to verify this. There are bugs in both 6.6.0 and 6.7r100 which can cause this problem when the PPM signal contains invalid (out of range) pulses. The code actually changed between those 2 versions, but the problem manifests itself in a different manner in the newer code (should be better, but still not great).
The problem is fixed as of r130. I recommend building that version or later, or making a change in ppm.c in the older versions. You can see the difference in line 114:
https://code.google.com/p/autoquad/sour ... c?r=95#114https://code.google.com/p/autoquad/sour ... ?r=130#114In tags/6.6.0/onboard version you could remove line 109:
https://code.google.com/p/autoquad/sour ... /ppm.c#109But the problem ultimately stems from some kind of interference in the PPM signal. I have one AQ board which also has poor quality with PPM input, also with FrSky Rxs (several different ones with either Rx firmware version). Seems to be something related to the ground circuit on the AQ, but my troubleshooting so far has been inconclusive. My LA captures always come up clean, and the same Rxs work fine on another AQ, so it's a mystery at this point. It still flies fine and I don't notice any problems in the air, but the PPM code needs to be fixed as I describe above.
I would try to isolate the noise issue by disconnecting everything else from the AQ board, using a very short cable to the Rx, and making a quick log. Also make sure it's not grounding against a standoff or screw, or something like that. If that fixes the quality then you can add connections back one at a time and see if you find the problem. You could also try powering the Rx from a BEC (keep ground and signal to the AQ), though that didn't help in my case. If none of that fixes it, as seems to be my case, then I'm not sure what to do next
-Max