FastFred,

If you have a new or different headset, or new or different radio, you might need to adjust the mic gain (first) or the sidetone on the radio itself.

When you speak of picking up helicopter noise in the transmission - that makes me think a look at the mic gain is a good place to start - might be set a little high.

Information on doing this is a bit skimpy in most radio manuals, however the David Clark headsets have some instructions in their headset manuals.

If you don't have a new or different headset or radio - might need to start somewhere else.

IMHO....Radio=Voodoo