On 8/27/2010 7:33 PM, larynl2 wrote: > This has always interested me, and I've never seen a good technical reason > for a loss of range with narrow deviation and receivers, either. > But<somewhere> one must exist. If it didn't, there'd be no reason not to > take analog deviation down to say, 1 kc., or 0.1 kc., would there?
There are several good references online. A good balance between theory and understandability is at: http://urgentcomm.com/networks_and_systems/mag/narrowbanding-system-coverage-effect-201004/ and http://www.adcommeng.com/Narrowbanding_for_Technicians.pdf Essentially as the modulation index goes down, the difference between the modulated signal and noise becomes lower, and so more signal strength (to better saturate the FM receiver's detector) is required to compensate. > And I don't think that knowing a repeater's tail signal strength doesn't > change is an apples to apples comparison. It is all about intelligibility of the modulated signal, not the quieting of the unmodulated signal. In fact, for the unmodulated case the narrower IF filters make narrowband *better*. Matthew Kaufman
