I was talking about 1kHz and 100 Hz deviation, not 2.5kHz.
On Fri, Aug 27, 2010 at 8:30 PM, wb6dgn <[email protected]> wrote: > "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 [email protected], 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 >> > >> > >> > >> > >> > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
