NFM vs FM?

[RedPenguin]

I'm looking at the database for PA (my area), but also NJ and NY.

Now, I remember reading stuff about the FCC saying defiantly narrowband mandated for public safety.

Though isn't NFM just the opposite of WFM? I mean, I always thought if it wasn't WFM, it's NFM. Though is there actually NFM, FM, and WFM?

For all the areas I checked in the database it just says "FM".

 

[zz0468]

Confusing, isn't it.

Technically speaking, if the modulation index is less than 1, it's narrow band fm. If the modulation is greater than 1, it's wideband fm. Aren't you glad you asked? Google "modulation index" if you really want to confuse yourself.

In the case of scanners, WFM is usually what you find with FM and analog TV broadcasting. Simply referring to it as FM would imply 5 KHz deviation, and narrow band FM is something less than that.

Ouside of dealing with scanners, and land mobile radio, the various terms can have varying meaning, so you have to understand the context in which it is used.

 

[RedPenguin]

Interesting...

Well, I was trying to find out if there is an easy way to find out, because I know when you do search and store or close call store on scanners, if you end up using the wrong FM mode, you most likely will not get the tone stored.

 

[rico47635]

Well, I was trying to find out if there is an easy way to find out, because I know when you do search and store or close call store on scanners, if you end up using the wrong FM mode, you most likely will not get the tone stored.

I may be wrong, but I am pretty sure that NFM, FM, WFM refers to the deviation allowed by the FCC. One thing you could do is research the specifications for different types of FM transmitters and see what the ratings are for deviation. For example, my ham radio specs say a deviation factor of +/- 5 kHz. I don't know what it would be for other types of transmitters, but finding this information out should give you an idea. In other words, if it turns out that the maximum deviation allowed for the commercial radios is +/- 2.5kHz, then you'd know to set your scanner to NFM for those frequencies. I hope this helps, again, I could be wrong. I am just taking a guess here.

 

[zz0468]

Well, I was trying to find out if there is an easy way to find out, because I know when you do search and store or close call store on scanners, if you end up using the wrong FM mode, you most likely will not get the tone stored.

Look up the FCC records. There is an emission designator on the license that specifies the authorized bandwidth. You'd do well to learn how to look it up, and understand what the license actually means.

 

[RedPenguin]

I've always looked it up....

Look up the FCC records. There is an emission designator on the license that specifies the authorized bandwidth. You'd do well to learn how to look it up, and understand what the license actually means.

I've always looked up the licenses, but I just never noticed any thing that said "NFM" OR "FM" or whatever.

Though I will give it another try.

EDIT: NVM, you just click on the frequency in question.....

 

[zz0468]

I've always looked up the licenses, but I just never noticed any thing that said "NFM" OR "FM" or whatever.

Though I will give it another try.

It's not going to say FM or NFM or whatever. You'll see a column on the license labeled "Emission designator" and it will list something like 20k0F3E. That means 20 KHz bandwidth, Frequency modulation, single channel (not multiplexed), telephony, i.e. voice.

Here's a nifty little chart you could use for decoding the emission designators:

http://www.comsearch.com/articles/emission.pdf

20 KHz would be 5 KHz deviation. 12k or 6K would indicate narrow fm deviation.

 

[qlajlu]

I'm looking at the database for PA (my area), but also NJ and NY.

Now, I remember reading stuff about the FCC saying defiantly narrowband mandated for public safety.

Though isn't NFM just the opposite of WFM? I mean, I always thought if it wasn't WFM, it's NFM. Though is there actually NFM, FM, and WFM?

For all the areas I checked in the database it just says "FM".

I don't know if this will help or not, but Lou Maag, one of our Mods, has an explanation of WFM, NFM, and SNFM as it applies to scanning on this page in the RR Wiki.

 

[poltergeisty]

Gonna throw a monkey wrench in the gears and mention PFM. :twisted:

How does the FCC define ILS? :lol:

 

[RedPenguin]

Well then....

Well, I guess that almost every frequency in my area is non-narrow band.

Almost every frequency has an emission code of 20K0F3E.

It's only the brand new channels that Cambria County recently added that come up as 11K2F3E.

Though one frequency, 453.650 in this license (http://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=2944457) has both Emission codes.

 

[poltergeisty]

Oops! This is bandwidth, not modulation.

 

[N_Jay]

Confusing, isn't it.

Technically speaking, if the modulation index is less than 1, it's narrow band fm. If the modulation is greater than 1, it's wideband fm. Aren't you glad you asked? Google "modulation index" if you really want to confuse yourself.

In the case of scanners, WFM is usually what you find with FM and analog TV broadcasting. Simply referring to it as FM would imply 5 KHz deviation, and narrow band FM is something less than that.

Ouside of dealing with scanners, and land mobile radio, the various terms can have varying meaning, so you have to understand the context in which it is used.

DING DING DING, we have a winner.

 

[N_Jay]

I may be wrong, but .. . I am just taking a guess here.

Please read zz0468's first post.

 

[N_Jay]

Gonna throw a monkey wrench in the gears and mention PFM. :twisted:

That's not a "monkey wrench", its more of a outside pitch (in a football game).:roll::twisted:

How does the FCC define ILS? :lol:

How does that relate to this thread?

 

[poltergeisty]

Because ILS uses modulations... :lol:

What does in fact define the line between SNFM, NFM, WFM in terms of deviation?

 

[N_Jay]

Because ILS uses modulations... :lol:

What does in fact define the line between SNFM, NFM, WFM in terms of deviation?

Confusing, isn't it.

Technically speaking, if the modulation index is less than 1, it's narrow band fm. If the modulation is greater than 1, it's wideband fm. Aren't you glad you asked? Google "modulation index" if you really want to confuse yourself.

In the case of scanners, WFM is usually what you find with FM and analog TV broadcasting. Simply referring to it as FM would imply 5 KHz deviation, and narrow band FM is something less than that.

Outside of dealing with scanners, and land mobile radio, the various terms can have varying meaning, so you have to understand the context in which it is used.

Reading; It's fundamental!

 

[RedPenguin]

Well....

Well I have to admit, that I find it a little funny how the BCT15 and BR330T default to NFM.

Like I said almost every frequency in my area seems to be FM.

Alright, one frequency with a lot of activity sounds way better now that I switch it to FM.

It's funny, because my scanner always sounded slightly different than their radios, but now my BCT15 seems to match what I remember their own radios sounding like.

 

[N_Jay]

If everyone would start communicating in more accurate terms, either bandwidth or deviation, then it would be easy to understand what bandwidth or deviation matches what setting for your particular brand scanner.

If the discussion continues to focus on WFM, FM, NFM, VFFM, SNFM and other informal descriptors there will always be confusion.

 

[poltergeisty]

I understand what he wrote, but what defines each modulation by its deviation?

20 K is WFM?? 5K Is NFM? Etc...

Okay, so 1-5 is considered NFM 5 and higher is WFM? :lol:

 

[N_Jay]

The only 'technical" definition is for a modulation index of greater or less than 1.

All the rest are descriptions used in context, and will vary depending on the perspective of the person using it.

Essentially all analog LMR is various forms of "Narrow FM".
Almost all broadcast FM and analog TV Audio is various forms of "Wide FM"