I have a rather specific question regarding the operation of ADF receivers within Europe and specifically the UK. Currently I'm working on the comms system for a Level D FFS and have been asked to look at the ADF simulation.
We are looking at a defect report that states the audio tone used to replay the ADF ident is the wrong frequency. According to the ICAO, FAA regs, etc, the audio tone that is keyed to make the ident audible is either 400Hz or 1020Hz.
On all previous simulators we have used 1020Hz without comment, and have only used 400Hz in conjunction with the BFO or Tone switch to receive older non-modulated carrier NBDs.
However this time the test pilot we are working with has stated that the ADF tone is incorrect (the higher 1020Hz one), and that all ADF stations in the UK (and possibly much of Europe) should be heard using the lower 400Hz tone.
For reference, 1020Hz is the tone frequency used for VOR/ILS tones, while 400Hz is used for the ILS outer marker.
It would be very helpful if any pilots reading this could offer their opinions.
I realize that trying to recall what one tone versus another sounds like after the fact is tricky, but right now I have nothing.
Thanks, GY
