[Milsurplus] Aircraft comm/nav specs

[mstangelo at comcast.net]

The Europeans are handling channel congeston by using 8.33 khz channels:

http://en.wikipedia.org/wiki/Airband

I read years ago that the FAA wanted to bypass the 8.33 khz channel spacing and go digital.. Does anyone know what happened to this plan to digitize aeronautical voice communications?

Thanks,

Mike N2MS



Aug 24, 2010 05:37:26 PM, gl4d21a at juno.com wrote:

Jim:

I think you missed an order of magnitude here.

Ken:

When, in the late 1930s, VHF aircraft communications were originally fielded, it was not practical to insure that transmitters were closer to nominal channel frequency than 35 kHz (~.025%) or so.  Crystal tolerances, circuit tolerances, vibration, etc. were all limitations. The technology was just not there to build stable frequency control within the size, weight, ruggedness and cost constraints which existed.  So, aircraft channelization was set at 0.1 MHz (100 kcps in the lexicon of the day).  That was reduced to 0.05 MHz (50 kHz) sometime in the late 50s or early '60s IIRC, where it stood for a while, due to private aircraft owner reluctance to spend big money for better radios.  With present technology (read synthesizers) it is possible to build transmitters which will hold SSB frequency accuracy (think hams on two meter SSB or 432 or 1296 SSB for that matter) at VHF, and aircraft standards are slowly moving out of the dark ages.  Commercial aircraft have had radios whic
h could channelize at 7.5 kHz for years, which is about the width of an AM signal, but AOPA, well, they resist and they represent a lot of private pilots. 

HTH & 73
George
W5VPQ