"However, if you reduce the modulation and, at the same time, reduce the receiver bandwidth and audio recovery..."
Should be: However, if you reduce the modulation and, at the same time, reduce the receiver bandwidth and INCREASE audio recovery... Gettin' ahead of myself! --- In [email protected], "wb6dgn" <wb6...@...> wrote: > > > > 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" <larynl@> 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) > > > > > > > > > > > > > > > > > > > > > >
