Yup.  Because filtering is easier at 400Hz, I think design engineers get
a little sloppy when designing power supply DC filter circuitry.  You
can sure hear it on airplane public address systems!

Never got across 400Hz AC.  it must feel pretty weird to get vibrated
that fast!

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
>
>
>
>