"Mike" nospam @ aol.com wrote in message
...
| "Gerry Caron" wrote in message
| ng.com...
|
| "Bob Noel" wrote in message
| ...
| In article ,
| Tman wrote:
|
| What is that -- and does it matter to GA avionics? Heard it
referenced
| a few times in the sale of an older GIII. But Google does not turn up
| much.
|
| (It's not applicable in the USA.)
|
| It has to do with the lack of frequency protection for ILS. High
| power FM stations (in Europe) can bleed enough RF into ILS frequencies
| that ILS receivers (and technically VOR receivers) need to do a
| better job rejecting out-of-channel frequencies.
|
| It's an ICAO Annex 10 rule that requires ILS receivers installed after
Jan
| 2001 (?) to have improved FM Immunity. As Bob said, it requires a
tighter
| spectral mask on the receivers to better reject bleed over from adjacent
| channels. It can be a real issue for CAT II/III ops. Since Part 25 a/c
| are normally certified for world-wide ops, they've had to meet it even
tho
| it wasn't a real problem in the US.
|
| As it turns out, it is needed in the US; but not for the original
reason.
| Since then our FCC approved HD radio standards that allow significantly
| more out-of-band emissions than the old analog signals. Just hope the
FAA
| hasn't installed an ILS on 108.1 MHz near a 107.9 MHz HD station.
|
| Proper frequency management would probably prevent a problem. Even if it
| didn't, it wouldn't take long for the FAA to figure out there was a
problem.
| Even if the problem wasn't discovered by a PIREP, all ILS systems are
| periodically flight checked.
|

You have a tremendous grasp on the obvious little mikey.