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ao-40 downlink question

I have assembled an ao-40 2.4ghz downlink setup using a (plastic) direcPC
dish, a downconverter from K5GNA, and a 6 1/2 turn helix feed (1/2 turn is
matching) . The receiver is yaesu ft-847 w/2.1khz crystal filter on ssb.
With the sat at a range of approximately 60,000km the best signal I can get
in ssb mode is an S5 with noise floor at S1+  listening to middle beacon(?)
or telemetry . CW copied at about S7 with the 500hz filter cut in. SSB qso's
are generally readable but not strong, maybe an S3. The helix was tweaked
using a wiltron site master so I know the helix after mounting has a swr of
1.1:1 at 2401.

My question is, would my receive signal strengths be considered normal for
the dish, feed, and other equipment I am using? Perhaps someone with a
similar setup?

Some info I have seen has suggested that the helix be closer to 8 turns to
match the illumination angle of the dish which I measure to be around 65
deg. I have also slapped some aluminum foil on the dish which didn't seem to
change things either way, varied the distance of the helix from the dish
center, etc.

Any constructive comments would be appreciated..

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