|> >It's due to a simple fact that AM preceded FM and that AM is what was available when airplanes began using radios.
|>
|> Then why did the land-mobile services (which started our using AM)
|> switch to FM?
|>
|> I think the best answer so far was that FM's capture effect would
|> be detrimental, if not dangerous, to air-ground comms.
|>
|>
|> Jeff NH6IL
It still has little to do with FM capture effect. It's purely economic.
How old is the average airplane? How old is the average car that uses land-mobile radio service? And how much $$ does an aircraft radio cost compared to one suitable for a car? And typically it's the government user that uses land-mobile radio services who can decide to spend the $$$ because it's only tax dollars they are spending, not their own personal dollars.
Cars are replaced every few years, and end-users of land-mobile (typically government/taxi/police/fire) buying cars/trucks can make that switch to new radio technolgies with little or no economic impact. Not so with airplanes. Airplanes are NOT replaced regularily, and thus there is a huge economic cost for someone to mandate that airplanes *will* switch to the imcompatible FM mode.
And it would have had to have been mandated for *everyone* to switch to FM due to the incompatibilities between AM and FM
There are too many AM radios in airplanes, and when there was shortlived talk of FM for airplanes, it was thorougly trounced by a broad spectrum of airplane drivers/owners/operators for purely economic issues.
Subject : Re: Why is aviation COM VHF *amplitude* modulated?
In <CwJxnD.51n@odin.corp.sgi.com> jerryb@jerber.sandiego.sgi.com (Jerry Bransford) writes:
>There are too many AM radios in airplanes, and when there was shortlived talk of FM for airplanes, it was thorougly trounced by a broad spectrum of airplane drivers/owners/operators for purely economic issues.
What would an (FAA accepted?) FM radio cost? What is the total
anual cost (hangar/ground space, inspections, maintenance, fuel) of
operating a single engine plane? Is a radio upgrade going to break the
bank? What is the cost of a new radio as a percentage of yearly (or
even amortize it over 5 years) operating expenses? I'm not saying your
wrong, just curious about yearly operating costs.
I'd suspect the hobby of aviation has just as many people reluctant
to "upgrade" as does the hobby of amateur radio. I still hear local
repeater chatter regarding the "problem" of "upgrading" your HT
to PL when one's favorite repeater moves from "carrier only access"
to full-time "PL tone" access. As if PL is some high-tech luxury!
