July 30th, 2018

After I noticed some spots for SR1KOL in JO74SE on 1296.960 MHz, I monitored the frequency using WSJT-X Wide Graph. About 400 Hz below the nominal frequency traces of a F1 signal can be seen, when airplanes cross the path to the beacon. The signal is not audible, but I am pretty sure, it is SR1KOL.

Traces of SR1KOL in JO74SE, “1000” = 1296.960 MHz. The strong signal at the very left is a birdie.

Some information can be found on the website of Polski Klub UKF: It is located on a high rise building in Kołobrzeg, 40 m above ground. The power is 3 W into a slot antenna. Beacon keeper is Andrzej, SQ1GU.

The video shows an A380 crossing the path between DJ5AR and SR1KOL. At minute 2:00 the plane crosses the first time and at minute 4:00 after a turn it crosses a second time. Mind the traces at 580 Hz in the waterfall diagram. The 1000 Hz mark corresponds to 1296.960 MHz.

Irek, SP5MX, who was involved in building the beacon and who repaired it recently, told me, the beacons reference is an OCXO withtout any GPS-lock. So possibly the beacon may transmit 400 Hz lower than defined.

At least in the morning of July 31st audible reflections could be heard via an Airbus A330. This time the 1000 Hz mark correspondents to 1296.9596 MHz.

After 10 seconds the noise becomes a kind of ‘musical’. Another 10 seconds later experienced ears can hear the tone.