OpsLog/app_sat_track_test.go

package main

import (
	"testing"

	"hamlog/internal/sat"
)

// The dial arithmetic has to be the exact inverse of the correction, or every
// touch of the knob would nudge the nominal frequency a little further off and
// the uplink would walk across the passband over a pass.
func TestSatNominalFromDialRoundTrip(t *testing.T) {
	// A range of range rates: hard approach, drifting, hard recession. ±8 km/s
	// covers a low orbit overhead.
	for _, rate := range []float64{-8, -3.2, -0.4, 0, 0.4, 3.2, 8} {
		p := sat.Position{RangeRate: rate}
		for _, nominal := range []int64{29_450_000, 145_900_000, 435_850_000, 10_489_675_000} {
			sh := sat.Doppler(p, nominal, 0)
			factor := -rate / satLightKmS
			got := satNominalFromDial(sh.DownHz, factor)
			if diff := got - nominal; diff > 1 || diff < -1 {
				t.Errorf("rate %.1f km/s, %d Hz: heard %d, came back as %d (%+d)",
					rate, nominal, sh.DownHz, got, diff)
			}
		}
	}
}

// SAT_MODE is what goes on a QSL card, and the letters are the uplink's then
// the downlink's — the order operators write and the order ADIF wants.
func TestSatModeLetters(t *testing.T) {
	for _, tc := range []struct {
		name     string
		up, down int64
		want     string
	}{
		{"FO-29: 2 m up, 70 cm down", 145_950_000, 435_850_000, "V/U"},
		{"AO-91: 70 cm up, 2 m down", 435_250_000, 145_960_000, "U/V"},
		{"AO-7 mode A: 2 m up, 10 m down", 145_900_000, 29_450_000, "V/A"},
		{"QO-100: 13 cm up, 3 cm down", 2_400_175_000, 10_489_675_000, "S/X"},
		{"receive only", 0, 145_800_000, ""},
	} {
		if got := satModeLetters(tc.up, tc.down); got != tc.want {
			t.Errorf("%s: got %q, wanted %q", tc.name, got, tc.want)
		}
	}
}

// Azimuth-only tracking must not command the rotor once a second.
//
// The step check used to compare BOTH axes, so with the elevation never
// commanded its difference stayed above the step for the whole pass and every
// tick sent the antenna to the bearing it was already on. A rotator is a
// mechanical thing with a finite number of turns in it.
func TestPointRotatorAzOnlyIgnoresElevation(t *testing.T) {
	rec := &countingRotator{}
	tr := &satTracker{rot: rec, rotStep: 5, rotAzOnly: true}

	// The satellite climbs while the bearing barely moves — a pass going
	// overhead from the side, which is the shape that provoked this.
	for _, p := range []sat.Position{
		{Az: 100, El: 5},
		{Az: 101, El: 20},
		{Az: 102, El: 45},
		{Az: 103, El: 70},
	} {
		tr.pointRotator(p, false)
	}
	if rec.n != 1 {
		t.Errorf("azimuth-only sent %d commands for 3° of bearing, want 1", rec.n)
	}
	if rec.lastAz != 100 {
		t.Errorf("commanded azimuth %v, want the first one", rec.lastAz)
	}

	// And it still follows the azimuth when the azimuth actually moves.
	tr.pointRotator(sat.Position{Az: 130, El: 70}, false)
	if rec.n != 2 {
		t.Errorf("a 30° swing was not followed: %d commands", rec.n)
	}
}

// With an elevation axis, a climb is still followed.
func TestPointRotatorFollowsElevationWhenItCan(t *testing.T) {
	rec := &countingRotator{}
	tr := &satTracker{rot: rec, rotStep: 5}
	tr.pointRotator(sat.Position{Az: 100, El: 5}, false)
	tr.pointRotator(sat.Position{Az: 101, El: 40}, false)
	if rec.n != 2 {
		t.Errorf("a 35° climb was not followed: %d commands", rec.n)
	}
	if rec.lastEl != 40 {
		t.Errorf("commanded elevation %v, want 40", rec.lastEl)
	}
}

type countingRotator struct {
	n              int
	lastAz, lastEl float64
}

func (c *countingRotator) Point(az, el float64) error {
	c.n++
	c.lastAz, c.lastEl = az, el
	return nil
}
func (c *countingRotator) Heading() (float64, float64, bool, error) { return 0, 0, false, nil }
func (c *countingRotator) Close()                                   {}

// Which sideband goes on each slice.
//
// An inverting transponder turns the passband over, so a signal transmitted on
// lower sideband comes back on upper. Setting USB at both ends put the
// operator's own audio through upside down — unreadable at the far end, and on
// FO-29, RS-44 and AO-73 that is every contact attempted.
func TestSatSidebands(t *testing.T) {
	cases := []struct {
		name           string
		tp             sat.Transponder
		wantDown, want string
	}{
		{"inverting linear: LSB up, USB down",
			sat.Transponder{Mode: "SSB", Inverting: true}, "USB", "LSB"},
		{"non-inverting linear: USB both ways",
			sat.Transponder{Mode: "SSB"}, "USB", "USB"},
		// A tone is transmitted and received in FM whichever way the passband
		// runs, and CW is CW.
		{"FM is FM both ways", sat.Transponder{Mode: "FM"}, "FM", "FM"},
		{"CW ignores inversion", sat.Transponder{Mode: "CW", Inverting: true}, "CW", "CW"},
	}
	for _, c := range cases {
		down, up := satSidebands(c.tp)
		if down != c.wantDown || up != c.want {
			t.Errorf("%s: got %s/%s, want %s/%s", c.name, down, up, c.wantDown, c.want)
		}
	}
}