"As receiver bandwidth narrows, higher frequency stability is required. Handhelds with ovenized reference oscillators are not very practical."
TCXOs are more than adequate to do the job. Typical frequency stability for a +-5.0kC system is 5ppm. TCXOs of 0.5ppm are common and not terribly expensive; more than 2.5 times more stable than conventional wisdom would claim necessary for 6.25kC bandwidth. If you use a good tight receiver with a reasonably quiet front end, there should be NO appreciable difference in range; the NB system could even be a bit better. Tom --- In Repeater-Builder@yahoogroups.com, DCFluX <dcf...@...> wrote: > > 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...@...> 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 > > > > > > > > >
