debug(motor-antenna): trace the follow band-gate decision (why the antenna did/didn't move)

app.go

@@ -11990,6 +11990,8 @@ func (a *App) ultrabeamFollowNow(freqHz int64) {
 		return
 	}
 	if !motorBandAllowed(s.Bands, freqHz) {
+		applog.Printf("ultrabeam: followNow %.3f MHz is %q — not in covered bands %v; no move",
+			float64(freqHz)/1e6, bandForHz(freqHz), s.Bands)
 		return // a band the antenna doesn't cover — leave it where it is
 	}
 	khz := int(freqHz / 1000)
@@ -14448,6 +14450,7 @@ func (a *App) startUltrabeam() {
 	if s.Follow {
 		stop := make(chan struct{})
 		a.ubFollowStop = stop
+		applog.Printf("ultrabeam: follow loop starting — covered bands %v, step %d kHz", s.Bands, s.StepKHz)
 		go a.ultrabeamFollowLoop(a.motorAnt, s.StepKHz, s.Bands, stop)
 	}
 	if s.TXInhibit {
@@ -14635,15 +14638,21 @@ func (a *App) ultrabeamFollowLoop(c motorAntenna, stepKHz int, bands []string, s
 			// follow loop chases. If the antenna QSYs unexpectedly, this shows the
 			// CAT backend started reporting that frequency (e.g. WSJT-X moved the
 			// dial, or the active slice changed) even though you didn't touch the VFO.
-			if rigKHz != lastRigKHz {
+			newFreq := rigKHz != lastRigKHz
+			if newFreq {
 				applog.Printf("ultrabeam: follow loop reads rig freq %.3f MHz (mode %s) — antenna at %d kHz, step %d kHz",
 					float64(rs.FreqHz)/1e6, rs.Mode, st.Frequency, stepKHz)
 				lastRigKHz = rigKHz
 			}
 			// Skip bands the antenna doesn't cover (per the operator's band list) —
 			// no tune command, so the elements stay where they are on 80 m, an
-			// un-fitted 30 m, etc.
+			// un-fitted 30 m, etc. Log the decision once per QSY so "why did/didn't
+			// the antenna move" is answerable from the log.
 			if !motorBandAllowed(bands, rs.FreqHz) {
+				if newFreq {
+					applog.Printf("ultrabeam: %.3f MHz is %q — not in covered bands %v; leaving the antenna put",
+						float64(rs.FreqHz)/1e6, bandForHz(rs.FreqHz), bands)
+				}
 				continue
 			}
 			// Deadband reference = the rig freq we LAST commanded a move for, not the