Re: Signal at high speed (was: Re: [NSW] Guards & Mobile phones)

["Chris Downs" <cvdowns@ozemail.com.au>]

So what frequency are we talking about - hertz, kilohertz, megahertz?

By my calculations (thank god this ain't no exam):

If the frequency is 1 hertz then the wavelength is 300,000,000m.  To reach
the receding train in 1 second the extra distance is approx. 300,000,083.3m
or the frequency is increased to approx 1.000 000 28 hertz - I doubt this is
significant.

However if the frequency is 1 megahertz then the wavelength is 300m.  To
reach the receding train in 1 second the extra distance is still approx.
83.3m or the frequency is increased to approx 1.28 megahertz - this sounds
significant, is it?

I know SFA about the transmission of radio waves so who can help?

Chris

David Bromage <dbromage@fang.omni.com.au> wrote in message
Z1qV4.433$lX1.662824@news0.optus.net.au">news:Z1qV4.433$lX1.662824@news0.optus.net.au...
> Chris Downs (cvdowns@ozemail.com.au) wrote:
> > How significant is the Doppler effect in a train travelling at 83.3m/s
> > (300km/h) compared with the speed of radio waves 300,000,000m/s (approx
1.1
> > billion km/h)?
>
> Forget the speed of radio waves, go by the wavelength (i.e. subcarrier
> frequency).
>
> kkCheers
> David