One more thought:  We've discussed 25Hz AC for railroads and the like.
I believe I recall hearing somewhere that when Edison finally understood
that Westinghouse/Tesla had won, he began producing 16Hz AC.  Talk about
power supplies with iron!

Mike Freeman < K 7 U I J >

On Thu, 13 Nov 2003 [log in to unmask] wrote:

> 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
>
>
>
>