[Elecraft] Why some satellites reverse the sidebands

[Paul Stoetzer]

Though there may be technical reasons behind it, the biggest reason is
practical.

If you don't invert the sidebands, the total Doppler shift is the sum
of the shift on two bands. For a satellite in a standard LEO orbit
with an uplink at 2 meters and downlink at 70 cm, the total Doppler
shift is +/- 3.5 kHz on 2 meters and +/- 10 kHz on 70 cm. If the
sidebands were not inverted, the total Doppler shift through the pass
would be +/- 13.5 kHz. If you invert the sidebands, the total Doppler
shift is the difference between the shift on two bands, or +/-  6.5
kHz. That's far easier to deal with if you're compensating for the
Doppler shift manually.

73,

Paul, N8HM
On Mon, Sep 3, 2018 at 9:13 AM Jim Rogers <jim.w4atk at gmail.com> wrote:
>
> A common LO (local Oscillator) for the receiver and the transmitter is
> the only reason I can think of.
>
> Jim
>
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