[BC] Re: Oscopes and Bessel null, FM modulation

[Dana Puopolo]

FM overmodulation by measuring deviation is such a relative thing, it
shouldn't be enforced, except in really obvious situations.

I see it like the speed limit. The speed limit on the highway is 65, yet to
keep up with traffic you have to do 70. NONE of the people doing 70 will be
ticketed (nor should they be), yet the guy who's observed by the police
wailing by them doing 80 will be cited. 

The only thing that matters is occupied bandwidth anyway. Excessive occupied
bandwidth will cause interferennce to your adjacent neighbor (but then again,
so does IBOC - and THAT's allowed).

Just my 2 cents...

_D


------ Original Message ------
Received: 
From: Xmitters at aol.com
To: broadcast at radiolists.net
Subject: [BC] Re: Oscopes and Bessel null, FM modulation

In a message dated 7/21/06 12:00:38 AM Central Daylight Time, 
broadcast-request at radiolists.net writes:

<< If the higher-order sidebands are a result of excessive carrier deviation 
--  
 one component of FM bandwidth.  As a rough approximation, Carson's Rule 
 states that ~ 98% of occupied bandwidth can be determined by use of the 
 following formula:
 
 BW  =  2(Dmax + Fmax)
 
 Perhaps it's for the reason you mention that the FCC interprets 
 over-modulation as exceeding one peak per ten-second interval, or six peaks 
 per minute.  This allows for a relatively generous margin of error whether 
 the error is truly in the transmission, or in the measurement.
 
 Paul >>
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