Tor,
That too is a liability in public safety work: the systems' attempts to compensate conceal the deteriorating signal path from the user. He/she has no warning of the impending demise of the talk path. There is a reason that the FAA and the airline industry have stayed with AM and SSB. Concurrent signals can sometimes both be understood by the human brain and the signal generally degrades in a noticeable way prior to becoming unreadable.
Tom Horne schrieb:
There are surely more reliable ways to signal a deteriorating signal than to rely on what you hear.
Actually, they have not. Even air traffic control systems struggle with network capacity and the FAA approved CPDLC system (Controller Pilot Data Link Communications) has been in operation for almost 10 years now, offering a digital replacement for voice communication between the ATC center and the aircraft. Also several other security relevant ATC systems rely on digital communication, like e.g. TCAS (Traffic Collision Avoidance System). In case of a collision warning, the orders from the TCAS system even have priority above potential orders from the human air traffic controller. One of the direct causes for the mid-air collision above Überlingen, Germany in 2002 was that one of the pilots decided to follow the (probably analog transmitted) order from the ATC center instead of the automatic TCAS warning.
Sometimes, and if not, you may end up with something like the Tenerife accident in 1977, which was caused by poor radio reception and interference between two simultaneous transmissions.
Tor
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