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[aprssig] Field Day ISS APRS Contacts? Doppler

Morten Johansen morten at bzzt.no
Thu Jun 21 22:54:07 UTC 2012


Den 22. juni 2012 kl. 00.38 skrev david vanhorn:
...
> The doppler effect does not know which end(s) are moving, it is only about relative motion, so as the distance is decreasing, doppler shift is always up  and as distance is increasing doppler is always down, regardless of who is speaking.
> 
...

You forget that doppler shift is the same for  both ends, and only the ground end can account for it.
Since the satellite RX is "stuck" at the set frequency, you have to TX on a lower frequency for it to "see it" at the correct frequency (while it's approaching you).

And when it transmits as it approach you, it does that on the set frequency and you see it on a higher frequency.

It does make sense :)

-- 
LA1FTA Morten




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