[Milsurplus] FM Terminology

[Glen Zook]

Then in 1957 the FCC "split" lowband and highband and reduced the deviation to +/- 5 kHz with a "drop dead" date in 1962 except for public safety which had until 1967 to get the equipment compliant.  However, everyone had to drop the deviation but did not have to modify the audio characteristics to meet the new standards until the "drop dead" date.  The +/- 5 kHz deviation was then called "narrowband".  The 450 MHz to 470 MHz was "split" in 1967 and everyone had a "drop dead" date in 1972.  However, everyone had to immediately reduce the deviation from +/- 15 kHz to +/- 5 kHz immediately.

For those of use who were around for the first round of "narrowbanding", the new requirements, also called "narrowbanding", cause a "mental glitch"!
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: "gl4d21a at juno.com" <gl4d21a at juno.com>
To: MillerKE6F at aol.com 
Cc: RAFANTINI at salisbury.edu; milsurplus at mailman.qth.net 
Sent: Friday, February 10, 2012 5:33 PM
Subject: [Milsurplus] FM Terminology
 
Wideband is different from wideband.

Some of you will recall I posted this before.  WW2 MILSPEC "wideband" FM was about +/-100 kHz deviation. Closer to broadcast standard than land mobile radio.  Sometime earlier than 1953, land mobile "wideband" FM was limited to +/-15 kHz deviation, and receivers couldn't handle the wider swing of the MIL transmitters.  Vice-versa was OK, just "weak" audio.

HTH & 73,
George
W5VPQ


---------- Original Message ----------
From: MillerKE6F at aol.com
To: RAFANTINI at salisbury.edu, milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] RT-67/68 and the like
Date: Fri, 10 Feb 2012 16:16:04 -0500 (EST)

RE: GRC 7,8 etc.  

    Wide Band FM aside, the transmitters in these  things are stable beyond 
belief so I don't think that was a problem. Keep in  mind that most of the 
land mobile stuff in the early 50s was also Wide Band fm  so I think it was 
merely a choice at the time based on the technology  base.  The design of 
these monsters was quite exotic with heterodyne  schemes and so on for both tx 
and rx.   As to reliability, these old  war horses would probably stand up 
well against the later RT 524 things the Army  adopted and me thinks the RT 
524 is damn near as heavy as the GRC-8 unit.  (snip)

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