diff --git a/internal/cat/icomserial.go b/internal/cat/icomserial.go
index 7a69484..eab8ca7 100644
--- a/internal/cat/icomserial.go
+++ b/internal/cat/icomserial.go
@@ -93,18 +93,15 @@ type IcomSerial struct {
 	// leading main/sub selector byte (IC-7610/9700). scopeAmp is the latest
 	// reassembled sweep; scopeMu guards it (written by the scope goroutine, read
 	// via ScopeData from the binding goroutine).
-	dualScope bool
-	// Which 0x27 subcommand switches the waveform stream on this rig: 0x11 where
-	// it exists, 0x10 on the ones that answer 0x11 with a rejection.
-	scopeOutSub byte
-	scopeMu     sync.Mutex
-	scopeAmp    []byte
-	scopeLow    int64 // spectrum left-edge frequency (from the sweep's header frame)
-	scopeHigh   int64 // spectrum right-edge frequency
-	scopeSeq    int
-	scopeOn     bool
-	scopeFixed  bool // true = fixed-span mode (tracked optimistically)
-	scopeSeen   bool // logged the first sweep's structure once (on-rig verification)
+	dualScope  bool
+	scopeMu    sync.Mutex
+	scopeAmp   []byte
+	scopeLow   int64 // spectrum left-edge frequency (from the sweep's header frame)
+	scopeHigh  int64 // spectrum right-edge frequency
+	scopeSeq   int
+	scopeOn    bool
+	scopeFixed bool // true = fixed-span mode (tracked optimistically)
+	scopeSeen  bool // logged the first sweep's structure once (on-rig verification)
 
 	curFreq     int64     // last frequency read (for sideband choice)
 	curModeByte byte      // last raw Icom mode byte (for filter re-send)
@@ -1023,7 +1020,10 @@ func (b *IcomSerial) execScope(what string, sub byte, args ...byte) error {
 	if err == nil || !strings.Contains(err.Error(), "rejected") {
 		return err
 	}
-	if err2 := try(!b.dualScope); err2 == nil {
+	err2 := try(!b.dualScope)
+	applog.Printf("icom scope: %s rejected in the %s form — the other form gave: %v",
+		what, map[bool]string{true: "27 xx 00 …", false: "27 xx …"}[b.dualScope], err2)
+	if err2 == nil {
 		b.dualScope = !b.dualScope
 		applog.Printf("icom scope: %s rejected — this rig wants the %s form (selector=%v)",
 			what, map[bool]string{true: "27 xx 00 …", false: "27 xx …"}[b.dualScope], b.dualScope)
@@ -1050,32 +1050,15 @@ func (b *IcomSerial) SetScope(on bool) error {
 		// radio, and closing OpsLog (SetScope(false)) blanking a local IC-7300's
 		// screen is exactly the regression this avoids. Some firmwares don't ack a
 		// 0x27 set; a timeout isn't fatal, so log and continue.
-		if b.scopeOutSub != civ.SubScopeOnOff {
-			if err := b.execScope("display on", civ.SubScopeOnOff, 0x01); err != nil {
-				applog.Printf("icom scope: display on ack: %v", err)
-			}
+		if err := b.execScope("display on", civ.SubScopeOnOff, 0x01); err != nil {
+			applog.Printf("icom scope: display on ack: %v", err)
 		}
 	}
 	// Waveform data OUTPUT over CI-V: enabled with the scope, and — crucially —
 	// the ONLY thing we switch off on disable, so the radio's own scope display is
 	// left exactly as the operator had it.
-	//
-	// scopeOutSub is 0x11 on the radios that have it. The IC-7851 does not: it
-	// rejects 0x11 in both shapes, because on that radio 0x27 0x10 is itself the
-	// waveform-output switch rather than a display switch. Fall back to it, and
-	// from then on switch it off on disable too — on THAT radio doing so stops a
-	// data stream, not the operator's own scope screen.
-	if b.scopeOutSub == 0 {
-		b.scopeOutSub = civ.SubScopeOn
-	}
-	err := b.execScope("data output", b.scopeOutSub, boolByte(on))
-	if err != nil && b.scopeOutSub == civ.SubScopeOn && strings.Contains(err.Error(), "rejected") {
-		applog.Printf("icom scope: no 0x27 0x11 on this rig — 0x27 0x10 is its data-output switch")
-		b.scopeOutSub = civ.SubScopeOnOff
-		err = b.execScope("data output", b.scopeOutSub, boolByte(on))
-	}
-	if err != nil {
-		applog.Printf("icom scope: output on=%v ack: %v", on, err)
+	if err := b.execScope("data output", civ.SubScopeOn, boolByte(on)); err != nil {
+		applog.Printf("icom scope: output on=%v ack: %v — turn the CI-V trace on (Settings → CAT) and send the log", on, err)
 	}
 	b.scopeMu.Lock()
 	b.scopeOn = on