Narrow FM needs often a clean band. In Germany the repeaters for police, fire brigade and so on have always a clinically pure part, so they use this solution. Equal if analog or digital. HAM-Radio bands are always polluted with strange signals from neighbors in cause of their cheap toys form China, disturbing LED lamps and other electronical things which are often self imported and not at the demanded standard. Often I saw that the situation in America isnt better. To run against, the solution to be digital at the frequencies was often a good decision here. Thats why I am for the direct use of C4FM, to suppress the disturbations for having clean QSOs..
I have been looking for a replacement IC-92AD for a while now. I have some accessories for it. Mine took a drop from, and could not be repaired. Icom isn't making them anymore, and most of the ham outlets don't have any new ones in stock. I wasn't on D-Star much, but since I have the accessories, I'd like to find another. I was also looking at the VGC VR-N76 for APRS. The last time I did anything with APRS there were wires and cables everywhere. It looked like a server passed gas and exploded. There are a lot of choices out there now as far as radios go. And it has been 20+ years also since I did anything with APRS and I wouldn't even know where to begin. Also, a lot of the hams I knew are SK now, and the repeaters are more quiet than they are active. Sure, there's Echolink, but I'd still like another 92AD. If I don't find one I may spring for that N76. I'm reading the reviews on that one now.
Might as well use broadcast 75 Totally agree. There are about 7 repeaters in my local area. 5 of them are completely 99.99999% silent and the other two get used about an hour a week. There are far too many repeaters.
Is it really? I mean, if money were involved, I would agree. Frequency coordination outside the amateur service generally works really well because it has to and because people are paid to do it. The amateur community could have supported a national approach in the infancy of FM. They (or at least the ARRL board at the time) left it to become a hodgepodge of local approaches and bandplans. Efforts to establish standards have been a miserable failure. The National Frequency Coordinators' Council was the most ineffective organization with which I had experience in my 27.5 years as a radio amateur. No one mourned its death sometime around/before 2016. Against that backdrop, and with so much water under the bridge, why not accept a generally accepted list?
What kind of reasoning is that? You have more than one radio than you need, but you can't use two at the same time. And yet you buy more. Many people think that the repeaters are a service and if there are enough of them, you don't need any more. No, this is about building and experimenting. There are not just 7 OMs or groups who want to do this! But I know that plug-in amateur radio operators can't understand that. 73, Peter - HB9PJT
No, the range remains the same. The receiver sensitivity at 12.5 kHz is 3 dB better than at 25 kHz. Why do you assume that the range is lower with 12.5 kHz? Can you please prove this? 73, Peter - HB9PJT
What generally accepted list? In my area RepeaterBook is nearly useless. Maybe it's good in KS or other areas where they accept accurate repeater data.
i am good for narrow...since one person in eastern Nebraska has most of the rptr pair in his name....but for rptrs that no one monitors...
You are wrong. Plenty of documentation exists from technical sources explaining why. None of this makes sense, especially for the amateur service which isn't suffering from capacity issues nor is there any mandate to refarm like what went down in part 90 in the USA. Again, a solution in search of a problem. Reading is fundamental.Plenty of people involved with part 90 narrowbanding of public safety systems have chimed in and concurred with these findings. In case you missed it: See page 4 of the above document: Narrowbanding of analog radio systems will cause a loss of coverage. The outer fringes of your radio coverage will most likely be affected. Simply put, where you once had coverage now you don’t. This is perhaps, the most negative functional impact of narrowbanding. Most field users learn their radio systems over time, and for the most part they know where radios work and where they do not. This process is going to change your coverage. The cause of this phenomenon is related to the physics of the narrower signal, but it’s not as important as knowing where and if you can expect it to happen. It is recommended that as a part of the planning process computer coverage contours are prepared. These models can give you a good idea of how fixed base sta- tions and repeaters will likely be impacted. Digital radio systems are not expected to experience a loss of coverage as a result of narrowbanding. Still, a computer propagation model can be a very useful tool to ensure that is indeed the case. The computer propagation model in Figure 3 illustrates the effects of phase 1 narrowbanding. The red and green color contours together illustrate the coverage that is generally expected in the wideband 25 kHz environment. The green only illustrates the expected coverage after narrowbanding to 12.5 kHz. Everywhere shaded in red is lost coverage area once the switch is made to narrowband operation. As you can see, the model predicts lost coverage along several roads. The time to discover the loss is not during an emergency. This type of modeling can be very valuable for educating users about what to expect and predicting coverage needed to assist decisionmaking.
N4NXD, thanks for your information. I find references on the internet that less transmission power is required for FMN, which means that the coverage is better with the same transmission power. So exactly the opposite of your coverage map. I have also done tests and found that FMN requires slightly less transmission power. In my tests, however, the difference is negligible at 1-2 dB. Here is a reference from an article: https://www.mwrf.com/technologies/e...73/comparing-narrowband-and-wideband-channels “As a result, typically higher transmit signal power is needed in a wideband channel to overcome the noise level-as well as other factors, such as signal propagation losses-so that a significant signal level will appear at the receiver and meet the receiver's minimum signal-to-noise-ratio (SNR) performance requirements for reception and processing.” Perhaps FMN narrowband did not work so well in the past with the old systems due to poorer filters and large frequency tolerances? 73, Peter - HB9PJT
There literally thousands of part 90 licensees who went from 25KHz to 12.5KHz in the USA. An agency near me spent over $2 million USD to narrowband their VHF conventional repeaters, comparators, and receivers. Guess what: they lost coverage EXACTLY as shown in the example above. All of their infrastructure were modern stations, quality filters, and adequate TX/RX separation (no 600KHz ham splits, most repeaters were 5MHz to as much as 11MHz) and they experienced poorer portable coverage, especially on the outskirts. Their solution was to join a costly regional 700/800MHz P25 system and replace all sites with 700MHz and obviously coverage problems ended, and they now have secure voice on all talk groups, but it cost over $16 million more to implement. We don't need to go through that painful experience when there isn't a problem with available spectrum. Most repeaters here in metro Atlanta, GA sit silent for days- explain WHY this is needed again?
Perhaps there is confusion in what is meant by 12.5kHz and 25kHz? 12.5 kHz channels versus 12.5 kHz bandwidth? 12.5 kHz channels need a narrow bandwidth around 11kHz. As the bandwidth gets too narrow one loses the advantages of FM. Wideband FM can be useful for high quality voice. 200 kHz WBFM on 10GHz can sound very good.
The common reference in LMR means narrowing transmit bandwidth to 2.5KHz max vs. 5KHz max, and RX bandwidth from 25KHz down to 12.5KHz. The part 90 systems had to drop TX bandwidth down to 2.5 from 5, and RX bandwidth accordingly. Many licensees using analog FM quickly discovered their radios sucked. Whether it's subscriber equipment, infrastructure, combo of both, the experience on narrow was less than wide. Less coverage, less audio quality, and in a public safety environment, this means busting out a few millions and scrapping legacy analog and going to 700/800 onto P25 pastures. All for what. Nothing gained. In amateur radio, there is no frequency crises. Maybe a bunch of good old boy paper repeaters being hogged by piggish coordinators, but the 2m, 220 and 440 bands are hardly "packed full" of users getting "bonked" like some NYPD dispatch channel. It just isn't happening to justify changing every single user to 2.5KHz. For it to work, and no one get interference, EVERYONE would have to migrate a la what part 90 had to back in 2013. Again, a solution in search of a problem.
The ironies here. In another thread there are folks railing against 6kHz wide SSB. At the same time advocacy for wider FM. Interesting
