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Re: re: C-C Rider Revisited



C-band (5650-5850 MHz) is optimal for an in-band transponder as the frequencies
can be separated by almost 3.5%. On S-band (2400-2450 MHz) the maximum
separation is only 2%.

DSP can be used to cancel Doppler shift on the uplink by tracking the carrier of
each uplink signal and translating each to a fixed downlink frequency. DSP can
also demodulate and remodulate the signal as terrestrial repeaters do and
improve the SNR by 3 dB. Once this is done the uplink and downlink modulation
can be different.

The ground station must still compensate for downlink Doppler shift on the
downlink. If the downlink signal has a reference carrier this can be done
automaticly.

73,

John
KD6OZH

----- Original Message -----
From: "**THE-RFI-EMI-GUY**" <rhyolite@nettally.com>
To: <kd6ozh@verizon.net>; <amsat-bb@AMSAT.Org>
Sent: Sunday, 10 October, 2004 18:00 UTC
Subject: re:[amsat-bb] C-C Rider Revisited


> While I haven't read the followup article, the original one did catch my
> interest. I sketched out an S band version (SST or S-S Transponder?)
> which could be feasible as well. (I know the article dismisses s-band).
> What I don't understand is the use of DSP to correct doppler unless it
> is implemented at the ground station.  How is that accomplished?
>
> --
> Joe Leikhim K4SAT
> "The RFI-EMI-GUY"
>
> The Lost Deep Thoughts                        By: Jack Handey
>      Before a mad scientist goes mad, there's probably a time
> when he's only partially mad.  And this is the time when he's
> going to throw his best parties.
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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----
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