Message-Id: <20031113184200.WMDK17368.imf20aec.mail.bellsouth.net@[68.212.98.27]> Martin wrote: >As for why aircraft use 400 HZ, you are all right but there is >even one more reason. While I don't know why the exact number of >400 Hertz, the biggest reason for using a higher frequency is the >size of inductors such as what you have in motors and transformers. <snip> >I think that we'd get pretty tired of hearing that mosquito >whine everywhere very quickly. I get my share of aeronautical mobiles check in with me when I'm ncs for the Maritime mobile service net and you always hear a hint of that 400 hz and its harmonics. Also note that on hf a lot of the aero comms sound like there's a little rf feedback into the audio. Harder to get a good ground up there <grin>. 73 de nf5b Richard Webb Electric Spider Productions "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." --- Benjamin Franklin, NOvember 1755 from the Historical review of Pennsylvania