[ARC5] A-10 Radios

[jeepp]

One, if not the salient point, is that aeronautical radio was established as AM.  Changes have been considered considered by ICAO, and earlier groups, on a number of occasions but global economics was high on the list.  The cost to convert tens of thousands of aircraft and ground stations would be horrendous.  Save for bandwidth, stability, and numbers of channels, not much has changed.  Currently, the US has 720 channels with 25 kHz spacing.  The Europeans now have mandated 8.33 kHz spacing for the high altitude structure with the attendant additional channels.  Me thinks data-link and full ADS-B in/out installation will probably decrease any need for more channels in the 118-136.995 spectrum. We'll see.Jeep K3HVG


Sent from my Verizon 4G LTE smartphone

-------- Original message --------
From: Richard Knoppow <1oldlens1 at ix.netcom.com> 
Date: 7/10/18  17:48  (GMT-05:00) 
To: arc5 at mailman.qth.net 
Subject: Re: [ARC5] A-10 Radios 

    Experience with police radio on VHF is that if two mobile 
stations get on at once both can be blocked. While FM tends to 
favor the stronger signal (called capture ratio) its a mess when 
they are close to the same strength.

On 7/10/2018 1:59 PM, Bart Lee wrote:
> FM received by a mobile (or air mobile) vehicle can "washboard" 
> the received signal as the moving vehicle hits the incoming radio 
> waves. Car radios on FM frequently have this issue. Aviation AM 
> may or may not have been selected to avoid this problem, at 135 
> MHz and below. AM was the way aviation radio started, so there 
> was some lock-in, especially after Curtis LeMay selected single 
> sideband for SAC in the early 1950s. SSB's power advantages may 
> also have come into play.  73 de Bart, K6VK ##
> -- --
> Bart Lee
> ​, K6VK, CHRS, AWA, ARRL​


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL
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