diff --git a/changelog.json b/changelog.json
index 6f5d53e..ee9c8c1 100644
--- a/changelog.json
+++ b/changelog.json
@@ -5,12 +5,12 @@
     "en": [
       "Each radio carries its own MY_RIG (Settings → CAT), written on every QSO made with it — ahead of the per-band station in Operating conditions, which says what you planned to use rather than which radio is keying. Left empty, nothing changes.",
       "Worked-before matrix: a dot in the corner of a cell now means the callsign you are working has already been worked on that slot, whatever colour the entity status gave the cell. Its two colours (worked / confirmed with this callsign) are in Appearance with the other matrix colours.",
-      "Icom spectrum scope: the IC-7851 (and any radio that wants the main/sub selector on its scope commands) now works over CI-V — the command shape is worked out from the radio’s own answer instead of a list of models."
+      "Icom spectrum scope: the command shape (with or without the main/sub selector) is now worked out from the radio’s own answers instead of a list of models. A radio that has scope control but no waveform stream over CI-V — the IC-7851 — says so in the panel rather than showing a black rectangle."
     ],
     "fr": [
       "Chaque radio porte son propre MY_RIG (Réglages → CAT), inscrit sur chaque QSO fait avec elle — avant la station par bande des Conditions de trafic, qui dit ce qui était prévu et non quelle radio émet. Laissé vide, rien ne change.",
       "Matrice des contacts : un point dans le coin d'une case indique que l'indicatif en cours a déjà été contacté sur ce créneau, quelle que soit la couleur donnée par le statut de l'entité. Ses deux couleurs (contacté / confirmé avec cet indicatif) se règlent dans Apparence avec les autres couleurs de la matrice.",
-      "Scope Icom : l'IC-7851 (et toute radio qui attend le sélecteur main/sub sur les commandes de scope) fonctionne maintenant en CI-V — la forme de la commande est déduite de la réponse de la radio au lieu d'une liste de modèles."
+      "Scope Icom : la forme des commandes (avec ou sans le sélecteur main/sub) est déduite des réponses de la radio au lieu d'une liste de modèles. Une radio qui pilote son scope mais ne l'envoie pas en CI-V — l'IC-7851 — l'indique dans le panneau au lieu d'afficher un rectangle noir."
     ]
   },
   {
diff --git a/frontend/src/components/IcomPanel.tsx b/frontend/src/components/IcomPanel.tsx
index bdcd6f4..c4066b8 100644
--- a/frontend/src/components/IcomPanel.tsx
+++ b/frontend/src/components/IcomPanel.tsx
@@ -292,6 +292,9 @@ function ScopePanadapter() {
   const wfRef = useRef<HTMLCanvasElement>(null); // waterfall
   const peakRef = useRef(160); // running amplitude ceiling for auto-scale
   const holdRef = useRef<number[]>([]); // per-bin peak-hold line
+  // Some radios control their scope over CI-V but never stream it (IC-7851).
+  // Saying so beats a black rectangle, which reads as a bug in OpsLog.
+  const [unsupported, setUnsupported] = useState(false);
   const spanRef = useRef({ low: 0, high: 0 }); // latest sweep edges, for click-to-tune
   const vfoRef = useRef(0);    // latest VFO frequency, for wheel-tune
   const centerRef = useRef(0); // scope centre we last set (for pan ◀/▶)
@@ -333,6 +336,7 @@ function ScopePanadapter() {
       if (!alive) return;
       try {
         const sw = await IcomScopeData();
+        if (sw?.unsupported) setUnsupported(true);
         if (sw && sw.seq !== lastSeq && sw.amp && sw.amp.length) {
           lastSeq = sw.seq;
           setFixed(sw.fixed);
@@ -543,7 +547,10 @@ function ScopePanadapter() {
           <Chip label={on ? 'ON' : 'OFF'} on={on} onClick={toggle} />
         </div>
       </div>
-      {on && (
+      {on && unsupported && (
+        <div className="px-3 py-2 text-xs text-muted-foreground">{t('icmp.scopeNoStream')}</div>
+      )}
+      {on && !unsupported && (
         <div className="p-3">
           <div className="rounded-xl overflow-hidden ring-1 ring-info/20 shadow-lg shadow-sky-500/5 bg-[#05070e]">
             <canvas ref={canvasRef} onDoubleClick={onDblClick}
diff --git a/frontend/src/lib/i18n.tsx b/frontend/src/lib/i18n.tsx
index 779cf37..665c809 100644
--- a/frontend/src/lib/i18n.tsx
+++ b/frontend/src/lib/i18n.tsx
@@ -127,6 +127,7 @@ const en: Dict = {
   'mx.tipCallConf': 'This callsign confirmed', 'mx.tipCallWork': 'This callsign worked (not confirmed)',
   'mx.tipDxConf': 'Entity confirmed (other callsign)', 'mx.tipDxWork': 'Entity worked (other callsign)',
   'mx.tipNone': 'Never worked', 'mx.tipClick': 'click to list the QSOs',
+  'icmp.scopeNoStream': 'This radio does not send its scope over CI-V — its own screen still works.',
   'mx.markWork': 'This callsign worked', 'mx.markConf': 'This callsign confirmed',
   'mx.tipThisCall': 'already worked with this callsign',
   'mx.tipThisCallConf': 'already confirmed with this callsign',
@@ -616,6 +617,7 @@ const fr: Dict = {
   'mx.tipCallConf': 'Cet indicatif est confirmé', 'mx.tipCallWork': 'Cet indicatif est contacté (non confirmé)',
   'mx.tipDxConf': 'Entité confirmée (autre indicatif)', 'mx.tipDxWork': 'Entité contactée (autre indicatif)',
   'mx.tipNone': 'Jamais contacté', 'mx.tipClick': 'cliquer pour lister les QSO',
+  'icmp.scopeNoStream': "Cette radio n'envoie pas son scope en CI-V — son propre écran fonctionne toujours.",
   'mx.markWork': 'Cet indicatif contacté', 'mx.markConf': 'Cet indicatif confirmé',
   'mx.tipThisCall': 'déjà contacté avec cet indicatif',
   'mx.tipThisCallConf': 'déjà confirmé avec cet indicatif',
diff --git a/frontend/wailsjs/go/models.ts b/frontend/wailsjs/go/models.ts
index b2d0a6a..0dc7623 100644
--- a/frontend/wailsjs/go/models.ts
+++ b/frontend/wailsjs/go/models.ts
@@ -1196,6 +1196,7 @@ export namespace cat {
 	    low_hz: number;
 	    high_hz: number;
 	    fixed: boolean;
+	    unsupported: boolean;
 	
 	    static createFrom(source: any = {}) {
 	        return new ScopeSweep(source);
@@ -1208,6 +1209,7 @@ export namespace cat {
 	        this.low_hz = source["low_hz"];
 	        this.high_hz = source["high_hz"];
 	        this.fixed = source["fixed"];
+	        this.unsupported = source["unsupported"];
 	    }
 	}
 	export class TCIPanelState {
diff --git a/internal/cat/cat.go b/internal/cat/cat.go
index 8aaf708..1dbb693 100644
--- a/internal/cat/cat.go
+++ b/internal/cat/cat.go
@@ -674,6 +674,12 @@ type ScopeSweep struct {
 	LowHz  int64 `json:"low_hz"`  // left edge frequency (0 when unknown)
 	HighHz int64 `json:"high_hz"` // right edge frequency (0 when unknown)
 	Fixed  bool  `json:"fixed"`   // true = fixed-span mode, false = center-on-VFO
+	// Unsupported: this radio refuses the waveform-output command, so there will
+	// never be a sweep. The IC-7851 does — its last firmware is from 2016, older
+	// than the CI-V waveform stream — while still answering the scope's other
+	// commands. Reported so the panadapter can say so instead of showing a black
+	// rectangle that looks like a bug in OpsLog.
+	Unsupported bool `json:"unsupported"`
 }
 
 // IcomState returns the current Icom DSP state, or (zero, false) when the active
diff --git a/internal/cat/icomserial.go b/internal/cat/icomserial.go
index eab8ca7..3a37c1c 100644
--- a/internal/cat/icomserial.go
+++ b/internal/cat/icomserial.go
@@ -93,15 +93,18 @@ 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
-	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
+	// Set when the rig rejects the waveform-output command in both shapes: it has
+	// no stream to give, and asking again on every enable is noise.
+	scopeUnsupported 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)
@@ -1058,7 +1061,17 @@ func (b *IcomSerial) SetScope(on bool) error {
 	// the ONLY thing we switch off on disable, so the radio's own scope display is
 	// left exactly as the operator had it.
 	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)
+		applog.Printf("icom scope: output on=%v ack: %v", on, err)
+		// Rejected in both shapes = the command does not exist on this rig, which
+		// is a permanent answer and not a bad guess on our part. Remember it: the
+		// panel can then say so, and we stop asking a radio that has already
+		// said no.
+		if strings.Contains(err.Error(), "rejected") {
+			applog.Printf("icom scope: %s does not stream its scope over CI-V — control commands only", b.model)
+			b.scopeMu.Lock()
+			b.scopeUnsupported = true
+			b.scopeMu.Unlock()
+		}
 	}
 	b.scopeMu.Lock()
 	b.scopeOn = on
@@ -1302,7 +1315,8 @@ func (b *IcomSerial) ScopeData() ScopeSweep {
 	for i, v := range b.scopeAmp {
 		amp[i] = int(v)
 	}
-	return ScopeSweep{Amp: amp, Seq: b.scopeSeq, LowHz: b.scopeLow, HighHz: b.scopeHigh, Fixed: b.scopeFixed}
+	return ScopeSweep{Amp: amp, Seq: b.scopeSeq, LowHz: b.scopeLow, HighHz: b.scopeHigh, Fixed: b.scopeFixed,
+		Unsupported: b.scopeUnsupported}
 }
 
 // exec sends a set command and waits for the rig's OK (FB) / NG (FA) ack.