As receiver bandwidth narrows, higher frequency stability is required. Handhelds with ovenized reference oscillators are not very practical.
On Fri, Aug 27, 2010 at 8:01 PM, Matthew Kaufman <matt...@matthew.at> wrote: > 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 > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
