Transmission1

Anyone aware of where to look for uplink / downlink frequencies between a local airport tower, and a similarly local transmitter site? Airport / tower is at a low level, and the antenna site appears to be on a local hilltop site. OFCOM SIS shows an 18 GHz microwave link, joining the 2, but latency between the tower frequency, and the ground UHF relay is non existent, suggesting that the uplink / downlink is analogue. That may well be the case, as the UHF relay has been operating for at least 35 years when I first started scanning. Its feasible to assume the uplink / downlink would be ROIP, but the complete lack of latency suggests otherwise. Listing on AM airband and FM UHF, the 2 audios are effectively in sync. UHF relay is most definitely at the airport, so not co-located on the hill top site.

Any suggestions on where to look?

OK, so with some more research and monitoring, using a radio with an RSSI meter, it might appear that the airband RX/TX is coming from the tower, rather than the hilltop site. That would figure for the near instantaneous re-broadcast on UHF. First thing in the morning, there is a whole range of radios tested, so may have a better listen to that with a watch on RSSIs, to see if one of the standby radios has a stronger signal which would indicate its coming from that hilltop site. Said site does have a airports comms hut with about 6 x whits stick VHF airband antenna, and a couple of shorter ones, most likely ADS-B. That said, there are about a similar number atop the control tower, so I think that's where the main radio is transmitting from.