Aircraft interferences

[moodz]

... you may be picking up interference from the "flux valve" sensor that is present on many aircraft ( typically wingtips ).

They are basically flux gates for compass correction to correct for magnetic field anomalies and yes they can generate an interfering magnetic field ( in most cases another flux valve ).

you would have to be pretty close to the aircraft though ... eg 30 meters or so.

https://www.youtube.com/watch?v=nRz3fbaIxxQ

[ivconic]

I haven't researched the subject, I'm probably going to guess something wrong... but other than the major and publicly known communication systems in aviation; I'm sure there are many secondary "service" or "system" radio communications that are not known to us, it doesn't mean that they are some kind of secret, but they just don't belong in the domain of enough interest for the general public to know something about it.
Here I mean first of all the technology that is present at the airport. Not every "radio" at the airport has to be used only for communication with airplanes.
There is probably a whole system of weather stations to measure this and that. It is known that there is also a radar system for flight control. Airports are probably additionally "surrounded" by security systems.
All in all; airports are the source of many different radio waves, interference, magnetic fields, etc.
I believe that most of it is no secret and that the details can be learned from someone who is directly involved and who knows the details.

[giuhalftrack]

and what about some sort of other "oscillator" not strictly related to radio communication ? but emitting EMI ?

I think the only way will be to go in the same place and "listen" with a device like the one suggested by ivconic

[ivconic]

and what about some sort of other "oscillator" not strictly related to radio communication ? but emitting EMI ?

I think the only way will be to go in the same place and "listen" with a device like the one suggested by ivconic

Bingo!
Acutally one can "foxhunt" it with it. Just attach proper antenna.