It handles azimuth and elevation, and a great many stations already run
it in front of a controller OpsLog has never heard of. For those,
OpsLog talking to the controller itself would be a second program
fighting PstRotator over the same cable — so it hands over the bearing
instead, and lets PstRotator turn the mast.
Both kinds sit behind one small interface, chosen in Settings. Neither is
more correct than the other: the right one is whichever the station
already has working.
The 450° overlap is deliberately NOT applied on the PstRotator path.
PstRotator knows which machine is on the other end and does its own; two
programs each deciding to go the long way round is exactly how an antenna
unwinds in the middle of a pass.
Position queries are asked at most every three seconds rather than on
every tick. A PstRotator query binds a socket and waits up to a second
and a half, and many setups answer nothing at all — so one silence is
enough and it stops asking, reporting the commanded position instead and
saying that is what it is.
EasyComm is what satellite rotator controllers agreed on, so a box that
works with SatPC32, Gpredict or Hamlib works here. Serial or TCP, and its
own settings rather than the HF rotator's: an az/el pair is a different
machine on a different port, and an operator who has both must not have
to choose.
A great many EasyComm controllers — the Arduino trackers above all —
accept commands and never say a word back. That is legal and common, so a
silent controller is not treated as a broken one: it is still driven, and
the last commanded position is reported in its place, marked as commanded
rather than read. A stuck rotator must not be able to hide behind an
order it never carried out, which is why the panel shows the antenna's
position beside the satellite's.
The 450° overlap is the reason a satellite rotator is worth having, so it
is used: a pass crossing north continues past 360 instead of unwinding
three quarters of a turn with the antenna sweeping the ground. Below the
configured elevation the mast is left alone — the numbers are right all
the way round the orbit, but a rotator that chases a satellite through
the far side of the earth spends the night turning, and a mast has a
finite number of turns in it.
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.
rouggy