diff --git a/core/cleanup.py b/core/cleanup.py
new file mode 100644
index 0000000..69f5d43
--- /dev/null
+++ b/core/cleanup.py
@@ -0,0 +1,46 @@
+# Provides a timed cleanup of the spot list.
+import logging
+from datetime import datetime, timedelta
+from threading import Timer
+from time import sleep
+
+import pytz
+
+
+class CleanupTimer:
+
+    # Constructor
+    def __init__(self, spot_list, cleanup_interval, max_spot_age):
+        self.spot_list = spot_list
+        self.cleanup_interval = cleanup_interval
+        self.max_spot_age = max_spot_age
+        self.cleanup_timer = None
+        self.last_cleanup_time = datetime.min.replace(tzinfo=pytz.UTC)
+        self.status = "Starting"
+
+    # Start the cleanup timer
+    def start(self):
+        self.cleanup()
+
+    # Stop any threads and prepare for application shutdown
+    def stop(self):
+        self.cleanup_timer.cancel()
+
+    # Perform cleanup and reschedule next timer
+    def cleanup(self):
+        try:
+            # Perform cleanup
+            for spot in self.spot_list:
+                if not spot.time or spot.time < datetime.now(pytz.UTC) - timedelta(seconds=self.max_spot_age):
+                    self.spot_list.remove(spot)
+
+            self.status = "OK"
+            self.last_cleanup_time = datetime.now(pytz.UTC)
+
+        except Exception as e:
+            self.status = "Error"
+            logging.exception("Exception in Cleanup thread")
+            sleep(1)
+
+        self.cleanup_timer = Timer(self.cleanup_interval, self.cleanup)
+        self.cleanup_timer.start()
\ No newline at end of file
diff --git a/core/constants.py b/core/constants.py
index 87ab3c8..c01e140 100644
--- a/core/constants.py
+++ b/core/constants.py
@@ -3,7 +3,10 @@ from data.band import Band
 # General software
 SOFTWARE_NAME = "Metaspot by M0TRT"
 SOFTWARE_VERSION = "0.1"
+
+# Todo make configurable
 SERVER_OWNER_CALLSIGN = "M0TRT"
+MAX_SPOT_AGE_SEC = 3600
 
 # Modes
 CW_MODES = ["CW"]
diff --git a/core/utils.py b/core/utils.py
index 541698f..8269276 100644
--- a/core/utils.py
+++ b/core/utils.py
@@ -22,7 +22,8 @@ def infer_mode_family_from_mode(mode):
     elif mode.upper() in DATA_MODES:
         return "DATA"
     else:
-        print("Found an unrecognised mode: " + mode + ". Developer should categorise this.")
+        if mode.upper() != "OTHER":
+            print("Found an unrecognised mode: " + mode + ". Developer should categorise this.")
         return None
 
 # Infer a band from a frequency in kHz
diff --git a/main.py b/main.py
index 4698d47..3a9bc34 100644
--- a/main.py
+++ b/main.py
@@ -1,6 +1,8 @@
 # Main script
 import signal
 
+from core.cleanup import CleanupTimer
+from core.constants import MAX_SPOT_AGE_SEC
 from providers.dxcluster import DXCluster
 from providers.gma import GMA
 from providers.hema import HEMA
@@ -10,15 +12,16 @@ from providers.sota import SOTA
 from providers.wwbota import WWBOTA
 from providers.wwff import WWFF
 
-
 # Shutdown function
 def shutdown(sig, frame):
     print("Stopping program, this may take a few seconds...")
     for p in providers: p.stop()
+    cleanup_timer.stop()
 
 
 # Main function
 if __name__ == '__main__':
+    print("Starting...")
     # Shut down gracefully on SIGINT
     signal.signal(signal.SIGINT, shutdown)
 
@@ -41,7 +44,9 @@ if __name__ == '__main__':
     # Start data providers
     for p in providers: p.start()
 
-    # todo thread to clear spot list of old data
+    # Set up timer to clear spot list of old data
+    cleanup_timer = CleanupTimer(spot_list=spot_list, cleanup_interval=60, max_spot_age=MAX_SPOT_AGE_SEC)
+    cleanup_timer.start()
 
     # Todo serve spot API
     # Todo spot API arguments e.g. "since" based on received_time of spots, sources, sigs, dx cont, dxcc, de cont, band, mode, filter out qrt, filter pre-qsy
@@ -49,6 +54,8 @@ if __name__ == '__main__':
     # Todo serve apidocs
     # Todo serve website
 
+    print("Startup complete.")
+
 
 # TODO NOTES FOR NGINX REVERSE PROXY
 # local cache time of 15 sec to avoid over burdening python?
diff --git a/providers/gma.py b/providers/gma.py
index 5e77fd7..70edc72 100644
--- a/providers/gma.py
+++ b/providers/gma.py
@@ -36,12 +36,15 @@ class GMA(HTTPProvider):
                         sig_refs=[source_spot["REF"]],
                         sig_refs_names=[source_spot["NAME"]],
                         time=datetime.strptime(source_spot["DATE"] + source_spot["TIME"], "%Y%m%d%H%M").replace(tzinfo=pytz.UTC),
-                        latitude=float(source_spot["LAT"]),
-                        longitude=float(source_spot["LON"]))
+                        latitude=float(source_spot["LAT"]) if (source_spot["LAT"] != "") else None, # Seen GMA spots with no lat/lon
+                        longitude=float(source_spot["LON"]) if (source_spot["LON"] != "") else None)
 
             # GMA doesn't give what programme (SIG) the reference is for until we separately look it up.
-            ref_info = self.REF_INFO_CACHE.get(self.REF_INFO_URL_ROOT + source_spot["REF"], headers=self.HTTP_HEADERS).json()
-            spot.sig = ref_info["reftype"]
+            ref_response = self.REF_INFO_CACHE.get(self.REF_INFO_URL_ROOT + source_spot["REF"], headers=self.HTTP_HEADERS)
+            # Sometimes this is blank, so handle that
+            if ref_response.text is not None and ref_response.text != "":
+                ref_info = ref_response.json()
+                spot.sig = ref_info["reftype"]
 
             # Fill in any missing data
             spot.infer_missing()
diff --git a/providers/http_provider.py b/providers/http_provider.py
index 4b7f41c..7fd69a5 100644
--- a/providers/http_provider.py
+++ b/providers/http_provider.py
@@ -1,8 +1,9 @@
 import logging
-from datetime import datetime, timezone
+from datetime import datetime
 from threading import Timer, Thread
 from time import sleep
 
+import pytz
 import requests
 
 from providers.provider import Provider
@@ -42,7 +43,7 @@ class HTTPProvider(Provider):
                 self.submit(new_spots)
 
             self.status = "OK"
-            self.last_update_time = datetime.now(timezone.utc)
+            self.last_update_time = datetime.now(pytz.UTC)
 
         except Exception as e:
             self.status = "Error"
diff --git a/providers/parksnpeaks.py b/providers/parksnpeaks.py
index 176fd1a..d394f2a 100644
--- a/providers/parksnpeaks.py
+++ b/providers/parksnpeaks.py
@@ -21,13 +21,12 @@ class ParksNPeaks(HTTPProvider):
         new_spots = []
         # Iterate through source data
         for source_spot in http_response.json():
-            print(source_spot)
             # Convert to our spot format
             spot = Spot(source=self.name(),
                         source_id=source_spot["actID"],
                         dx_call=source_spot["actCallsign"].upper(),
                         de_call=source_spot["actSpoter"].upper(), # typo exists in API
-                        freq=float(source_spot["actFreq"]) * 1000,
+                        freq=float(source_spot["actFreq"]) * 1000 if (source_spot["actFreq"] != "") else None, # Seen PNP spots with empty frequency!
                         mode=source_spot["actMode"].upper(),
                         comment=source_spot["actComments"],
                         sig=source_spot["actClass"],
diff --git a/providers/provider.py b/providers/provider.py
index 898fcea..ebb868b 100644
--- a/providers/provider.py
+++ b/providers/provider.py
@@ -2,14 +2,14 @@ from datetime import datetime
 
 import pytz
 
-from core.constants import SOFTWARE_NAME, SOFTWARE_VERSION
+from core.constants import SOFTWARE_NAME, SOFTWARE_VERSION, SERVER_OWNER_CALLSIGN
 
 
 # Generic data provider class. Subclasses of this query the individual APIs for data.
 class Provider:
 
     # HTTP headers used for providers that use HTTP
-    HTTP_HEADERS = { "User-Agent": SOFTWARE_NAME + " " + SOFTWARE_VERSION }
+    HTTP_HEADERS = { "User-Agent": SOFTWARE_NAME + " " + SOFTWARE_VERSION + " (operated by " + SERVER_OWNER_CALLSIGN + ")" }
 
     # Constructor
     def __init__(self):