[BC] Occupied Bandwidth measurements...

[Phil Alexander]

On 7 Oct 2007 at 15:24, R A Meuser wrote:

> Modulation monitors are not common on many parts of this planet, 
> spectrum analyzers are. You can very effectively set up a station with 
> just a spectrum analyzer, especially if the intent is to assure that it 
> fits within the allocation scheme. Modulation monitors are an arbitrary 
> way of guesstimating whether or not you are properly occupying the channel.
> 
> Ask Lyle about how many mod monitors give misleading information. In 
> such cases you need the spectrum analyzer anyway.
> 
> I have probably set up as many Fm stations with a spectrum analyzer 
> using occupied bandwidth measurements as I have with a mod monitor. I'll 
> take the spectrum analyzer any day. The USA is the only place I know on 
> the planet where this might cause legal problems (usually not) but then 
> modulation rules like many other FCC rules are written assuming 
> compliance will be left to the technically challenged.

If you use a spectrum analyzer AND an audio oscillator I would agree
that is the most accurate way (Bessel zero) but using the spec. an.
alone is questionable unless you have a good one and can look at the
narrow slice between 75-100kHz above and below carrier then it is a
matter of both vision and interpretation.

Of course we did Bessel zero calibrations "back in the day" using only
an oscillator and a modulation monitor. In fact, this was the method
recommended by GE for their early FM gear.

---------------------------------------------
Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037