GPS interference RW24 Manila
 

IATA has brought to the attention of the Civil Aviation Authority of the Philippines (CAAP) numerous reports of GPS interference/signalGPS interference/signal degradation mostly during the critical instrument approach phase (RNAV GNSS) to runway 24 of Manila (Ninoy Aquino) International Airport.

Havent really ever heard of TV towers or cell towers interfering with GPS before...

This is interesting "A 3rd suspect is again a TV broadcasting station of a very influential religious group in the Philippines. Letters have been dispatched after initial readings also indicate signals on the GPS frequency emanating from their compound."


https://www.icao.int/APAC/Meetings/2...emagneGilo.pdf

That may be a data link co-located with a TV broadcasting tower.

Some grotty installation job at the radio station probably

Why would they be broadcasting anything near GPS frequency?

Some religious group trying to jamb near their compound?

Probably not deliberately, could be a harmonic of some clock used in equipment leaking out due to damaged shielding or missing covers.

In the pre HDTV days one common clock in broadcast equipment was 13.5 Mhz. The ninth harmonic of that is 121.5 Mhz.

There was more than one reported incident of TV stations getting a call asking if there was a downed aircraft in their parking lot.

Both sides of the call usually were well aware of the actual probable source.

I was - many years ago - involved in hunting for TV transmitters with harmonics that could interfere with GPS in the UK - although we found some candidates, we didn't find any that caused substantial problems. However it is certainly possible for a TV transmitter to cause problems in GPS frequencies either due to its fundamental or harmonic. There is a really interesting paper on it -Interference of GPS signals: Influence of Licensed Transmitters on the GPS GPS Signal Quality in the Netherlands' Airspace. This is an old paper (2000) from two researchers at the Netherlands Research Laboratory. I can't post a link yet but if you type "NLR-TP-2000-226" in Google, it comes up as the third report..

Thanks...here is the link to the website NLR-TP-2000-226

and direct link to the paper: Influence of Licensed Transmitters on the GPS Signal Quality in the Netherlands' Airspace