FM Immunity

[Tman[_2_]]

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.
T

[Bob Noel[_5_]]

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.

I can dig up some references from work, but I'm not sure
how many are available for free.

[Gerry Caron[_2_]]

"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.

Gerry

[RST Engineering]

Hey Gerry ...

Isn't 108.1 a protected ILS test frequency like 108.0 for VOR test?

Although I agree; I got my instrument ticket in San Diego and the Genave
A200 was more than willing to provide music on approach into the back course
at Lindberg Field.

Jim



> 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.
>
> Gerry
>
>

[Mike]

"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.

[Maxwell[_2_]]

"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.

[Mike]

"Maxwell" <#$$9#@%%%.^^^> wrote in message
...
>
> "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.

You have a tremendous grasp on your package, Maxipad. That's why small
children are afraid of you on the bus, as they should be.