If you reduce the modulation without reducing the receiver bandwidth, then, yes, the range will be reduced. You have reduced the signal without also reducing the noise. However, if you reduce the modulation and, at the same time, reduce the receiver bandwidth and audio recovery, by a like amount, then I do not see how the signal:noise ratio, and therefore range, would change appreciably. So, my question is, when these comparisons are made, are the receivers also narrow band with appropriate bandpass filters and adjustment of the detector and audio amplifier circuitry to compensate for the reduced modulation level? There is more to "narrow-banding" a radio than just "turning down" the modulation. That's my main objection to using a converted 800 Maxtrac for a 900 repeater receiver UNLESS the other changes are made as well; and that involves a whole lot more work. Tom
--- In [email protected], "larynl2" <lar...@...> 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? > > And I don't think that knowing a repeater's tail signal strength doesn't > change is an apples to apples comparison. > > Laryn K8TVZ > > > > --- In [email protected], MCH <mch@> wrote: > > > > This makes no sense. On the same band, with the same power, and with the > > same modulation type (analog) there is no reason there should be any > > loss by lowering the deviation and narrowing the receiver. > > > > If there was a change, it is not due to making the bandwidth more > > narrow. Maybe the new equipment is not as 'robust' as the old equipment. > > (IOW, both were putting out 50W, but the new one has more energy > > off-frequency). Or, maybe your new equipment's receivers are not as > > sensitive as the old ones. > > > > A good test of apples-to-apples is to see if a repeater's tail is lower > > in signal strength than the modulated/repeated carrier, as you're > > comparing the same thing - a signal of lower deviation to one of higher > > deviation. You should notice no difference whatsoever. > > > > Joe M. > > > > Andrew Seybold wrote: > > > > > > > > > Bill one of the losses if a County fire department system which has 6 > > > simulcast repeaters( 150 MHz) operating on wide-band with about 85% > > > coverage of the County, and we put in three new channels (after almost 2 > > > years of coordination and finding the correct channels), we put them up > > > using the same sights and same output (50 watts erp) and using the same > > > antennasâ"the new 3 channels under talk the existing wide-band systems > > > by > > > at least 30 percent. We are in the process of adding 2 new sites to make > > > up the difference. > > > > > > > > > > > > I am glad that you did not have a problem but this is just one of > > > several which I have had a problem with, and I have become a believer in > > > lost coverage, I have yet to see a system that has not lost coverage, I > > > am glad that you have. > > > > > > > > > > > > Andy > > > > > > > > > > > > > > > > > > *From:* [email protected] > > > [mailto:[email protected]] *On Behalf Of *Bill Smith > > > *Sent:* Friday, August 27, 2010 5:58 PM > > > *To:* [email protected] > > > *Subject:* Re: [Repeater-Builder] Re: Seeking emergency system design help > > > > > > > > > > > > > > > > > > Andy, my comment was not directed at the professionals, such as yourself > > > and others I know personally that are on this list. They were based > > > on his stated requirement for a disaster recovery radio system. It's not > > > something to do cheap or without expert guidance. > > > > > > > > > > > > People keep commenting on losing range with narrowband systems. A large > > > UHF LTR system I installed and maintained lost no discernable range > > > switching from 5 KHZ to 2.5 KHz. All else was the same. Same antenna > > > system, same repeaters, same mobiles. They just pushed a button to bring > > > them to the new talkgroups. > > > > > > > > > > > > Bill > > > > > > KB1MGH > > > > > > ------------------------------------------------------------------------ > > > > > > *From:* Andrew Seybold <aseybold@> > > > *To:* [email protected] > > > *Sent:* Fri, August 27, 2010 5:39:21 PM > > > *Subject:* RE: [Repeater-Builder] Re: Seeking emergency system design help > > > > > > > > > The FCC is re-thinking the move to 6.25 KHz based on the fact that > > > narrow band systems (and I have done a few of them) lose about 30% of > > > the existing coverage AND the NEW FCC believes that broadband is what it > > > is all about in the futureâ"no matter that broadband cannot do simplex > > > or > > > any of the other stuff needed for LMR and public safety. > > > > > > > > > > > > And like a few others have said on hereâ"you have to narrowband but are > > > NOT required to move to digitalâ"P25 or anything else, I have just > > > completed several systems which use analog and we have moved them from > > > Wide to Narrow with no problemsâ"EXCEPT the coverage problems I > > > mentioned. > > > > > > > > > > > > Andy > > > > > > W6AMS > > > > > > (and btw there are professional LMR folks and consultants who work with > > > this stuff every day on this list, just because we are hams too does not > > > mean that we are not in the business as well) > > > > > > > > > > > > > > >
