The hard part of satellite tuning is not the arithmetic, it is deciding
who owns the dial. A tracker that forces both frequencies fights the
operator every time they turn the knob to follow a station across a
linear transponder; one that never touches the receiver leaves them
chasing a signal that slides nine kilohertz across a 70 cm pass.
So the operator owns the receiver and the tracker follows them. Every
second it asks the radio where the receiver actually is. Where it put it,
nothing has changed. Further than a dial-turn's tolerance, and the
operator has chosen a station: what they landed on is converted back into
a nominal frequency, and the transmitter is derived from that. Which is
the division of labour on a linear bird — the operator listens, the radio
does the sums.
Three ways to reach the radio, because a satellite pair is a shape of
operating rather than a manufacturer's feature. An IC-9700 or IC-9100 is
asked for its OWN satellite mode: it pairs main and sub, gives full
duplex, and keeps the dials linked the way its designers meant, which is
always better than an imitation built out of split. A Flex gets two
slices, A the downlink and B the uplink, created when missing, because
"slice B does not exist" is not something to make an operator fix at the
start of a ten-minute pass. Everything else gets the downlink, and is
told so — half the job announced beats half the job hidden.
What goes in the log is the NOMINAL pair. Two stations working each other
through a transponder read different numbers off their dials at the same
instant; the only figure they can both agree on is the transponder's own.
FREQ is the uplink and FREQ_RX the downlink — the one place a satellite
QSO differs from every other kind, and the reason FREQ alone cannot
describe one.
Three questions answered at once, because on a pass there is no time to
go looking for any of them: where the bird is, when the next one comes,
and what to tune. The map draws each satellite's footprint — the honest
answer to "can I hear it", since everything inside the circle has the
satellite above its horizon — and the selected one's path over the
ground. The pass list is every favourite in time order, the one in
progress in green.
The readout shows the corrected frequency large and the nominal one
beneath it. Only one of them, and an operator cannot tell a Doppler
correction from a mistuned transponder.
The map opens on the station rather than the Atlantic, and remembers
where it was left like the others. The panel is mounted only while its
tab is visible: it asks for the tuning once a second, and there is no
reason to compute an orbit nobody is looking at.
rouggy