diff --git a/changelog.json b/changelog.json
index 1133d83..1bf0464 100644
--- a/changelog.json
+++ b/changelog.json
@@ -10,7 +10,8 @@
       "Selecting a QSO shows the entity the QSO records, not one re-derived from its callsign — a 3Y0K contact logged as Bouvet showed the Antarctica matrix.",
       "Back-entering a QSO resolves the ClubLog exception at the CONTACT’S date, so a DXpedition entered months later gets the entity it had then.",
       "QRZ.com sends an island reference for an operator on one, and OpsLog read past it — it now fills the IOTA award reference before the QSO is logged.",
-      "Sync across PCs: point every OpsLog at one folder you already synchronise and your contacts follow you between machines."
+      "Sync across PCs: point every OpsLog at one folder you already synchronise and your contacts follow you between machines.",
+      "TCI: a station spotted by several operators is drawn once on the panorama instead of two or three times a few hertz apart."
     ],
     "fr": [
       "Ouvrir le panneau Awards ne tire plus plusieurs fois le journal entier en même temps — un gros log occupait brièvement des gigaoctets de mémoire.",
@@ -20,7 +21,8 @@
       "Sélectionner un QSO affiche l’entité que le QSO enregistre, pas une recalculée depuis l’indicatif — un 3Y0K logué Bouvet montrait la matrice Antarctique.",
       "Saisir un QSO a posteriori résout l’exception ClubLog à la date DU CONTACT : une DXpedition entrée des mois après retrouve l’entité qu’elle avait alors.",
       "QRZ.com envoie la référence d’île d’un opérateur sur une île, et OpsLog l’ignorait — elle remplit désormais la référence IOTA avant l’enregistrement du QSO.",
-      "Synchro entre PC : fais pointer chaque OpsLog vers un dossier déjà synchronisé et tes contacts te suivent d’une machine à l’autre."
+      "Synchro entre PC : fais pointer chaque OpsLog vers un dossier déjà synchronisé et tes contacts te suivent d’une machine à l’autre.",
+      "TCI : une station spottée par plusieurs opérateurs n’est tracée qu’une fois sur le panorama, au lieu de deux ou trois fois."
     ]
   },
   {
diff --git a/internal/cat/tci.go b/internal/cat/tci.go
index 3af8c0c..8bb132f 100644
--- a/internal/cat/tci.go
+++ b/internal/cat/tci.go
@@ -48,6 +48,19 @@ type TCI struct {
 	tx     bool
 
 	lastSig string // last logged state signature (log only on change)
+
+	// spotFreq is the frequency of the marker currently on the panorama for each
+	// callsign — the panadapter's own state, which TCI never reports back. It is
+	// what makes one spot per call possible: without it there is no way to know
+	// there is an older marker to delete.
+	spotFreq map[string]int64
+}
+
+func absInt64(v int64) int64 {
+	if v < 0 {
+		return -v
+	}
+	return v
 }
 
 const tciDefaultPort = 40001
@@ -100,14 +113,65 @@ func (t *TCI) Connect() error {
 	debugLog.Printf("TCI: connected to %s", url)
 	go t.reader(conn)
 	if t.spotsEnabled {
+		// Forget what we thought was on the panorama at the same moment the radio
+		// is told to drop it. Kept, the memory would suppress the next spot for
+		// each of those calls as "already drawn" onto a panorama now empty.
+		t.mu.Lock()
+		t.spotFreq = map[string]int64{}
+		t.mu.Unlock()
 		_ = t.send("spot_clear;") // drop any leftover spots from a previous session
 	}
 	return nil
 }
 
+// spotFreqTolHz is how far a re-spot of the same callsign may sit from the one
+// already on the panorama before it is treated as a move rather than the same
+// spot said again.
+//
+// Two spotters hearing the same CW station rarely agree to better than a couple
+// of hundred hertz, and every one of them produces a cluster line. Below this
+// they are the same spot and nothing is sent at all; above it the marker is
+// deleted and redrawn where the station now is.
+const spotFreqTolHz = 500
+
+// noteSpot records what the panorama is about to hold for a callsign and says
+// what has to be sent: whether to draw at all, and whether an older marker for
+// the same call must be deleted first.
+//
+// Separate from SendSpot so the rule can be tested without a radio — and
+// because the lock must be released before anything is sent: t.send takes t.mu
+// itself, Go mutexes are not reentrant, and sending while holding it would
+// deadlock the backend and take the rig offline.
+func (t *TCI) noteSpot(call string, freqHz int64) (draw, deletePrev bool) {
+	key := strings.ToUpper(strings.TrimSpace(call))
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	prev, had := t.spotFreq[key]
+	if had && absInt64(prev-freqHz) <= spotFreqTolHz {
+		return false, false
+	}
+	if t.spotFreq == nil {
+		t.spotFreq = map[string]int64{}
+	}
+	if len(t.spotFreq) > 4000 {
+		t.spotFreq = map[string]int64{} // bound memory on a long session
+		had = false                     // forgotten: nothing left to delete by name
+	}
+	t.spotFreq[key] = freqHz
+	return true, had
+}
+
 // SendSpot mirrors a cluster spot onto the TCI panorama (implements Spotter).
-// The radio replaces a spot that has the same callsign, so re-spotting updates
-// it in place. No-op when spot mirroring is disabled.
+// No-op when spot mirroring is disabled.
+//
+// ONE MARKER PER CALLSIGN. This code assumed the radio replaced a spot carrying
+// a callsign it already had; it does not. ExpertSDR keys a spot on its
+// frequency too, so a DX station spotted by three operators — 14025.00,
+// 14025.12, 14024.90, which is an ordinary minute on a cluster — was drawn
+// three times, a few pixels apart, and stayed that way.
+//
+// So the previous spot for the call is deleted before the new one is sent,
+// which is what the FlexRadio backend has always done (spot remove / spot add).
 func (t *TCI) SendSpot(s SpotInfo) error {
 	if !t.spotsEnabled {
 		return nil
@@ -116,6 +180,17 @@ func (t *TCI) SendSpot(s SpotInfo) error {
 	if call == "" || s.FreqHz <= 0 {
 		return nil
 	}
+	draw, deletePrev := t.noteSpot(call, s.FreqHz)
+	if !draw {
+		return nil // the same station said again by another spotter
+	}
+	if deletePrev {
+		// SPOT_DELETE takes the callsign alone. Not in the protocol PDF this
+		// backend was written from; confirmed against ars-ka0s/eesdr-tci, which
+		// lists SPOT (5 arguments), SPOT_DELETE (1) and SPOT_CLEAR (0) — the
+		// other two matching what already works here.
+		_ = t.send(fmt.Sprintf("spot_delete:%s;", call))
+	}
 	// TCI's SPOT command wants the colour as a signed 32-bit DECIMAL integer in
 	// 0xAARRGGBB order — NOT a "0x…" hex string (e.g. "spot:UN7GK,cw,14025000,
 	// -16776961,test;"). ExpertSDR silently drops a spot whose colour field it
diff --git a/internal/cat/tci_spot_test.go b/internal/cat/tci_spot_test.go
new file mode 100644
index 0000000..f716399
--- /dev/null
+++ b/internal/cat/tci_spot_test.go
@@ -0,0 +1,87 @@
+//go:build windows
+
+package cat
+
+import "testing"
+
+// The reported symptom: with spot mirroring on, the same station appeared two
+// or three times on the panorama.
+//
+// Its cause is not in OpsLog's spot pipeline — one cluster line produces one
+// SendSpot. It is that a popular DX station IS spotted two or three times, by
+// different operators within the same minute, and no two of them agree on the
+// frequency to better than a few tens of hertz. The backend assumed ExpertSDR
+// replaced a spot bearing a callsign it already had; it keys on the frequency
+// too, so each of those became its own marker.
+func TestSameStationSpottedBySeveralOperatorsIsDrawnOnce(t *testing.T) {
+	tci := &TCI{spotsEnabled: true}
+
+	draw, del := tci.noteSpot("UN7GK", 14025000)
+	if !draw || del {
+		t.Fatalf("first spot: draw=%v delete=%v, want draw and nothing to delete", draw, del)
+	}
+	// The same station, two more spotters, a few tens of hertz apart.
+	for _, hz := range []int64{14025120, 14024900} {
+		if draw, del := tci.noteSpot("UN7GK", hz); draw || del {
+			t.Errorf("re-spot at %d Hz: draw=%v delete=%v, want nothing sent — this is the duplicate marker", hz, draw, del)
+		}
+	}
+}
+
+// A station that really moves must still move on the panorama, and the marker
+// left where it was must go. Deleting first is the whole difference between
+// "the spot follows the station" and "the station collects markers".
+func TestAStationThatMovesReplacesItsMarker(t *testing.T) {
+	tci := &TCI{spotsEnabled: true}
+	tci.noteSpot("UN7GK", 14025000)
+
+	draw, del := tci.noteSpot("UN7GK", 14032000) // 7 kHz up: a real QSY
+	if !draw || !del {
+		t.Fatalf("after a QSY: draw=%v delete=%v, want the old marker deleted and a new one drawn", draw, del)
+	}
+	// And the new position becomes the reference, so spotters agreeing with it
+	// are quiet again.
+	if draw, _ := tci.noteSpot("UN7GK", 14032100); draw {
+		t.Error("a spot at the station's new frequency was drawn again")
+	}
+}
+
+// Case matters nowhere in ham radio, and the cluster is not consistent about it.
+func TestSpotMemoryIgnoresCase(t *testing.T) {
+	tci := &TCI{spotsEnabled: true}
+	tci.noteSpot("un7gk", 14025000)
+	if draw, _ := tci.noteSpot("UN7GK", 14025000); draw {
+		t.Error("the same call in another case was treated as a different station")
+	}
+}
+
+// Two different stations are two markers — the whole point of the panorama.
+func TestDifferentStationsEachGetAMarker(t *testing.T) {
+	tci := &TCI{spotsEnabled: true}
+	tci.noteSpot("UN7GK", 14025000)
+	draw, del := tci.noteSpot("ZD7BG", 14025050) // 50 Hz away, a different operator
+	if !draw {
+		t.Error("a second station near the first was swallowed as a duplicate")
+	}
+	if del {
+		t.Error("deleting by callsign would have removed a spot this station never had")
+	}
+}
+
+// The connection drops and comes back: Connect sends spot_clear, so the
+// panorama is empty. If the memory survived that, the next spot for each of
+// those calls would be suppressed as "already drawn" onto an empty panorama —
+// the operator's spots would simply stop appearing until they changed
+// frequency.
+func TestReconnectingForgetsWhatWasDrawn(t *testing.T) {
+	tci := &TCI{spotsEnabled: true}
+	tci.noteSpot("UN7GK", 14025000)
+
+	tci.mu.Lock()
+	tci.spotFreq = map[string]int64{} // what Connect does alongside spot_clear
+	tci.mu.Unlock()
+
+	if draw, del := tci.noteSpot("UN7GK", 14025000); !draw || del {
+		t.Errorf("after a reconnect: draw=%v delete=%v, want it drawn again and nothing deleted", draw, del)
+	}
+}