Path: utzoo!attcan!uunet!tektronix!tekcae!vice!georgep
From: georgep@vice.ICO.TEK.COM (George Pell)
Newsgroups: sci.electronics
Subject: Re: Re: economical to modify a scanner radio ?
Message-ID: <3014@vice.ICO.TEK.COM>
Date: 10 Nov 88 02:36:18 GMT
References: <4156@tekgvs.GVS.TEK.COM> <182@sunset.MATH.UCLA.EDU>
Reply-To: georgep@vice.ICO.TEK.COM (George Pell)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 29

In article <182@sunset.MATH.UCLA.EDU> hgw@math.ucla.edu (Harold Wong) writes:
>and <4156@tekgvs.GVS.TEK.COM> jans@tekgvs.GVS.TEK.COM (Jan Steinman) writes:
>><...the public safety services all seem to use FM (even Highway Patrol at 42 
>>MHz) but aircraft tend to use AM. (would anyone care to explain why?)...>
>>Capture effect.  You don't want to lose your contact with a 747 on final 
>Wouldn't noise and losing contact be more of a problem?  Just think of your
>AM radio in the car.  

Actually, the reason aircraft radios are AM is that it is an international
standard. All (commercial) aircraft (with radios) worldwide use the 118 to
136 Mhz AM band as their primary communication channel (and by the way, all
pilots must speak english, even in Moscow).  It is that way because it was 
agreed upon to be that way, and to change it would take the agreement of 
virtually every single country in the world, and would affect every control 
tower, airplane, and communication facility in the world.

An aircraft radio licensed in the US must be type approved by the FCC, and
also approved by the FAA.  That is why I just paid a kilobuck plus for what
is the equivalent of a $70 CB radio.

As far as noise and losing contact, yes, sometimes it is less than optimum.
But a 747 on final already has clearance to land, and can do so safely
even without a radio.  For that matter, there are thousands of planes out
there with no radios at all.  It just means they cannot land or operate
near major airports like Chicago, Seattle, LA, etc.  

geo
1958 Cessna 172
N3986F