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Old September 29th 04, 12:35 PM
GeorgeB
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On Sun, 26 Sep 2004 14:37:44 -0400, "Netgeek"
wrote:


"GeorgeB" wrote in message
.. .
Aviation radio is AM ... fwiw


Interesting that this is still the case.


It isn't really a "still the case" issue; the technology for FM is
agreed to be better and to offer many advantages. One if its major
advantages is the very significnat disadvantage that keeps it from
being considered.

FM has that WONDERFUL capture ratio. The stronger signal completely
takes over the receiver. A weaker signal on AM lets the receiver know
that there are 2 signals, considered a safety necessity AFAIK. It
will take some digital modulation with sophisticated algorithms to
replace the antiquated AM here.

As an example - I found an article that mentioned a "SAAS" system proposal
(as part of NASA's SATS program). Basically this is a GPS augmentation
system intended for small airports (Small Airport Augmentation System). We
already have WAAS (Wide Area Augmentation) and I don't know what happened to
LAAS (Local Area Augmentation) - but SAAS was intended to deliver a low-cost
system that could provide a "virtual ILS" at any small airport. The accuracy
was on the order of around 0.2 meters horizontal and 0.3 meters vertical -
allowing approaches to the smallest of airports (or grass strips, I
suppose?) to Category I (1800 ft. runway visual and 200 ft. ceilings)
minimums without mega-bucks worth of additional equipment....Wow!!! - not
far removed from the next step of an autoland system in light aircraft.


I believe that will come rather soon. In reality, WAAS is better than
expected, and could likely get you to ground effect 98% of the time
,,, and CFIT 2%. I've never seen my WAAS handheld (non-aviation) off
by more than 20 ft in elevation when it had a full view of the sky ...
South Carolina ... and that, I understand, matters.

George