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What Is FMN & NFM and Are They Equal or They Different?

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#4
Nobody ever agreed on the determination of narrow anyway. 25KHz spaced channels are still narrow compared to wideband FM, as in broadcast and radio mics. 12.5KHz, 8.33KHz and 6.25KHz, all in current usage are all narrow.
 
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#5
When dealing with professional two way radio systems, the modern/current standard is:

Wide FM = 25KHz channel width. 5KHz deviation. 20K0F3E emission designator.
Narrow FM = 12.5KHz channel width. 2.5KHz deviation. 11K0F3E (sometimes 11K3F3E) emission designator.


NFM = FMN when dealing with a radio scanner in the two way radio realm.
 

nd5y

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#6
When dealing with the RadioReference database and the bandwidth settings on most scanners:

WFM (Wide FM) = 200 KHz channel bandwidth and up to 75 kHz deviation. (used for commercial broadcast FM and analog TV audio, which had less deviation)
FM = 25 KHz channel bandwidth, 5K Hz deviation.
FMN or NFM = 12.5 KHz channel bandwidth, 2.5 KHz deviation.
 

SteveC0625

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#7
For a deeper understanding of what is currently considered FM and NFM, read back through the many threads in 2011 and 2012 on the subject leading to the 1/1/13 deadline for most Part 90 radio systems to be narrowband compliant.

We went through pretty much the same gyrations a couple of decades ago when the 25 Khz channel spacing was implemented. However, there was no internet or forums for all this massive discussion that takes place these days. It was kinda transparent to scanner folks back then because they really didn't even know that the change happened and the change was technically much less obvious to the crystal controlled scanners and the very early synthesized channel scanners of the day.

So the commonly used terms Wideband and Narrowband change with the times. Sometime in the future, we'll probably be required to move to the 6.25 Khz standard for analog conventional. The digital technologies will continue to evolve even further, but when 6.25 is implemented. we'll be referring to the existing 12.5 systems as Wideband and the 6.25 ones as Narrowband. Everyone will have forgotten that the "old" 25 Khz systems even existed.
 
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#8
It depends on which manufacturer you're talking about (or what source) as to whether they mean the same thing. Odds are they do, but there have been at least two "narrow FMs" since the 60s.

Some manufacturers use NFM to talk about the modern 11.2 kHz BW mode (not 12.5 kHz). Some use SFM (an abbreviation of the correct term SNFM per the EIA). Some use FMN. All may mean the same thing.



Key words in many of the above responses is current standard.
 
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#9
My preference is nd5y's. I deal with professional radio of all kinds not just comms, and WFM is my links, my radio mics, and in ear monitors - with similar spec to that quoted. I'm not sure where the dividing line between wide and narrow comes, but I don't think having an FM category works, because that is simply the mode - the additional letter being the bandwidth designator. Probably context has a lot to do with it. For absolute accuracy we should be looking at deviation, when in practice we're really talking centre channel frequency slots. Back in the 80s, Icom switched from 25KHz channels to 12.5KHz channels and they also tightened up the deviation spec, so that an old 25KHz channel radio with matching deviation would not be received by the new spec icom radios - the over deviation triggered a mute. I remember attempting to convince users that they either bought new radios, or spoke more quietly (almost as a joke, and many actually instructed their users to do exactly that!) Motorola, my other radio brand back then simply left their receiver spec the same for a couple of model generations, so old users were louder than new users. Daft, looking back, but it worked.
 
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#10
I don't think having an FM category works, because that is simply the mode
That is also a mode that is used still today by some ham radio linking and the military. I believe the emission designation is 30K0F3E or something close to that.

FM, WBFM, FM, NBFM, and SNFM are all still used.

Wide and Narrow are simply relative terms such as saying your car is compact or full sized. What was a compact car in the 70s is a full sized car today.

There is no specific line of division because the line keeps moving.
 
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#11
Standard FM is still used by most hams, NOAA Weather Radio, Marine, Part 90 Low Band , and some UHF Part 90 (I think). With the exception of the Home Patrol 2 scanners (again, I think) there really isn't a proper front end to properly receive NFM in the current crop of scanners.
 
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#12
FM is the mode, as opposed to AM, SSB, FSK and all the others. the W and the N are guides to the channel bandwidth. There's not really something called 'standard' FM because some particular bands have specifications that differ. Like as said, Marine vs business radio. Both FM. Both standard, in their bands, but there are legacy business systems that still use 25KHz channels - this was also a standard, just an older one.

I don;t get what you mean about not being proper front ends? In scanners there is rarely any way of changing receive deviation. It's preset and tends to be wide for broadcast FM, and narrower for 25KHz spaced FM comms channels. The 12.5KHz channels are simply received on the wider window, and the result is 1. slightly lower audio. 2 slightly more noise on a 12.5KHz channel, and the inability to discriminate between two 12.5KHZ channels if they are next to each other. The upshot being that a strong signal on 453.1375KHz will cut through on 453.125MHz, when a properly designed front end on a radio set offers much greater rejection. On a scanner it perhaps doesn't really matter.
 
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#13
Exactly, the front end of the scanner on VHF High is designed with a 25kHz bandwidth filter, so when a station transmits next to the monitored channel, it will bleed through and you will hear that signal too. It makes monitoring those splinter channels difficult at best and impossible a majority of the time. the x36HP scanners supposedly have a real 12.5kHz filter to remedy that.

This is a major issue in large metropolitan areas, as the pool of Part 90 VHF channels has been exhausted. While it is getting better due to a lot of big systems going to trunk systems, there is still a lot of legacy traffic on VHF High, and the issue still remains in a lot of the suburban and rural areas. And a lot of the Interoperability channels are also on these 12.5 kHz spacing channels, so monitoring them is "difficult" if there is an agency using a channel right next to it

I don't know how congested the spectrum is over there, you being in the UK,you may not have to deal with this as much as we do here in the "Colonies" :)
 
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#14
It's very congested in the cities, but less so in rural locations, as I guess it is stateside. I can't see many manufacturers putting money into scanners apart from expensive ones now digital is removing the listenable channels. I guess the filter problem is unlikely to go away for the mass market.
 
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#15
Standard FM is still used by most hams, NOAA Weather Radio, Marine, Part 90 Low Band , and some UHF Part 90 (I think).
In order, wrong, wrong, wrong, wrong, and wrong.

Those users all use Narrowband FM (NBFM) - 16K0F3E or 20K0F3E

Standard FM (30K0F3E) is used by a few ham radio links (backbones), the military. That's about it. There have not been any Land Mobile or general ham users of it since the 60's.

Also, the modern scanners do support NBFM well. In fact, it's SNFM that is not widely supported except for the BCDx36HP series.
 
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#16
There's not really something called 'standard' FM because some particular bands have specifications that differ.
Yes, there was and is an FM mode (no prefix). Read above as was posted more than once. It was the original FM mode.
 
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#19
No - FM is a mode. NFM (and WFM) is exactly the same mode. The extra letter indicates the bandwidth in general terms. FM means absolutely nothing at all without the deviation, in the same way people mis-label AM. LSB, and USB are both variations of the AM mode - even though my transmitter has all three switches.

FM is the mode that all the ones we're talking about are. Clearly, broadcast and narrow bandwidth FM are different, and a broadcast receiver isn't much good at receiving the tiny deviation a comms channel has - but they are BOTH FM.

FM was the original FM mode? That's like stating that English was the first English. We're talking about the difference between the English spoken in Liverpool and Suffolk. The AM equivalent could then be Irish, with a north and south variation.
 
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#20
No - FM is a mode. NFM (and WFM) is exactly the same mode. The extra letter indicates the bandwidth in general terms. FM means absolutely nothing at all without the deviation, in the same way people mis-label AM. LSB, and USB are both variations of the AM mode - even though my transmitter has all three switches.

FM is the mode that all the ones we're talking about are. Clearly, broadcast and narrow bandwidth FM are different, and a broadcast receiver isn't much good at receiving the tiny deviation a comms channel has - but they are BOTH FM.

FM was the original FM mode? That's like stating that English was the first English. We're talking about the difference between the English spoken in Liverpool and Suffolk. The AM equivalent could then be Irish, with a north and south variation.
Yes, FM is A mode. FM is also a modulation-specific segment of the FM mode - just as NBFM and SNFM denote certain characteristics, so does the absence of any letter before "FM". When FM came about, there was only one type of FM, so it was simply called FM. Today, there are many types of FM. All but one have additional letters with "FM" to denote the difference.

"FM was the original FM mode" makes sense when you know the difference between the terms. There is a difference between "FM" and "the FM mode". Clarifying:

FM (the designation) was the original FM mode (the modulation scheme).

I was not repeating myself in the terms. The terms happen to use the same letters. That's why one said "FM" and the other said "FM MODE".
 
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