diff --git a/drb-c2-core/app/internal/mqtt_handler.py b/drb-c2-core/app/internal/mqtt_handler.py
index 494dd4c..ab5ece4 100644
--- a/drb-c2-core/app/internal/mqtt_handler.py
+++ b/drb-c2-core/app/internal/mqtt_handler.py
@@ -111,6 +111,8 @@ class MQTTHandler:
                 "assigned_system_id": None,
                 "approval_status": "pending",
                 "node_type": payload.get("node_type", "fixed"),
+                "secondary_sdr_mode": payload.get("secondary_sdr_mode", "none"),
+                "sdr_count": payload.get("sdr_count", 1),
                 "enforce_override_timeout": payload.get("enforce_override_timeout", True),
                 "is_overridden": False,
                 "override_system_id": None,
@@ -141,6 +143,11 @@ class MQTTHandler:
             updates["node_type"] = node_type
             updates["enforce_override_timeout"] = enforce_timeout
 
+            if "secondary_sdr_mode" in payload:
+                updates["secondary_sdr_mode"] = payload["secondary_sdr_mode"]
+            if "sdr_count" in payload:
+                updates["sdr_count"] = payload["sdr_count"]
+
             if node_type == "portable":
                 updates["is_overridden"] = False
                 updates["override_system_id"] = None
diff --git a/drb-c2-core/app/models.py b/drb-c2-core/app/models.py
index f7233a2..4ddd692 100644
--- a/drb-c2-core/app/models.py
+++ b/drb-c2-core/app/models.py
@@ -62,6 +62,8 @@ class NodeRecord(BaseModel):
     last_seen: Optional[datetime] = None
     assigned_system_id: Optional[str] = None
     node_type: str = "fixed"  # fixed or portable
+    secondary_sdr_mode: str = "none"  # none | adsb | ais | op25_2 — requires a second physical SDR
+    sdr_count: int = 1  # self-reported by the node's checkin, best-effort
     enforce_override_timeout: bool = True
     is_overridden: bool = False
     override_system_id: Optional[str] = None
diff --git a/drb-c2-core/app/routers/nodes.py b/drb-c2-core/app/routers/nodes.py
index 8b7f85d..53d3378 100644
--- a/drb-c2-core/app/routers/nodes.py
+++ b/drb-c2-core/app/routers/nodes.py
@@ -195,6 +195,7 @@ async def assign_system(
 class NodeUpdateBody(BaseModel):
     node_type: Optional[str] = None
     enforce_override_timeout: Optional[bool] = None
+    secondary_sdr_mode: Optional[str] = None  # none | adsb | ais | op25_2
 
 
 @router.patch("/{node_id}")
@@ -227,6 +228,8 @@ async def update_node(
             }
             if updated_node.get("ppm_override") is not None:
                 push_payload["ppm_override"] = updated_node["ppm_override"]
+            if updated_node.get("secondary_sdr_mode") is not None:
+                push_payload["secondary_sdr_mode"] = updated_node["secondary_sdr_mode"]
             mqtt_handler.push_config(node_id, push_payload)
 
     return {"ok": True}