Federal Fire going narrowband?

[Pro-95]

Ok I just had a Federal Firefighter in my store today scanner shopping. He was very interested in the Pro-94/95. I asked him what he was interested in listening to and he indicated, only fire. Ok I have a pretty good collection of fire freqs. Then he mentions that the Federal Fire Agencies will be going narrowband in January. I asked him narrowband what? He really didn't know, only that it would be narrowband. I told him that I was aware that NDF (Nevada Division of Forestry) was joining onto the Washoe County 800Mhz EDACS system soon but that I was unaware of what the Feds may be going to.

So, anyone heard rumors or know what the Federal Fire Agencies are going to be going to in January?

 

[Thunderbolt]

They might be joining the nationwide federal government trunked radio system that is coming out, which is called the Justice Integrated Wireless Network (JIWN). This system will be narrowband P-25 digital, with select talkgroups being encrypted, and direct talkaround capabilities. I wonder if this is what he is referring to?

73's

Ron

 

[INDY72]

BIFC freqs as they are being renewed will be narrowband also.... its the trend now

 

[Pro-95]

So what exactly is narrowband? From what is said above it can be a trunked or conventional frequency. Is it another form a tuning like AM/FM etc as it pertains to the frequency and then the frequencies can be used from there?

From what I gathered in searching narrowband is only scanable by a narrowband reciever.?.?.?.?

 

[INDY72]

Narrow band is this.. here is the classic freq- 154.1600...
Here is the new narrowband version- 154.1675
Scanners can do narrowband, thus NFM (Narrowband FM)... and the newscanners do it with the proper 12.5, 6.25. 7.whatever spacing.... this can be conventional, trunked, analog, digital,... whatever... now if it uses ACSB or the like,.. then yes youll need special equipment to hear it.

So you see all narrowbanding is is narrowing the gap between the chans thus making more effecient usage of the bandwidth and spectrum available.

 

[N_Jay]

Federal frequencies are being "narrowbanded" much the same as the "Refarming" rulles that are being applied by the FCC to frequencies below 512 MHz.
The federal timeline is much shorter. Most (maybe all) federal agencies are planning on meeting this narrowbanding rule with the use of P25 systems.

 

[nmfire10]

Narrowband in simple terms:

Each "channel only uses 1/2 as much bandwidth, making room for more channels. Logically, 1/2 as much bandwidth used means twice as much available as before. Once everyone is narrowbanded, it effectivly doubles the number of available channels to be licensed.

 

[Pro-95]

Ok I suspected as such.

So can a not designed for narrowband, on the fly frequency tuning scanner such as the GRE radios follow narrowband, assuming that the frequencies being used are not side by side? As an example most of the GRE radios, round frequencies now and fine tune on the fly.

Also if speech requires a bandwith of "x" how is narrowbanding performed? Compression or low rate digital sampleing?

 

[N_Jay]

Ok I suspected as such.

So can a not designed for narrowband, on the fly frequency tuning scanner such as the GRE radios follow narrowband, assuming that the frequencies being used are not side by side? As an example most of the GRE radios, round frequencies now and fine tune on the fly.

Also if speech requires a bandwith of "x" how is narrowbanding performed? Compression or low rate digital sampleing?

Lets start by discussing the two types of narowbanding separetly.

1) Narrow FM (12.5 Khz)
2) P25

1) The narrow analog FM is acheived by reducing the deviation on the transmitter. Since the 25 KHz signal is several times wider thna teh 4 KHZ (or so) of modulation content ther system will continue to work with reduced signal to noise. Sometimes compression and expansion and/or other noise reduction techniques are applied to offset the effect of the bandwidth reduction.

A normal FM receiver will pick up these signals, but they will not be as loud, and the adjacent channel rejection specification will be MUCH worse.

2) P25 was designed to be a narrowband system (12.5 KKHz). The Vocoder rate and the channel coding scheme were selected to produce a a certain channel rate (9600 BPS). The modulation scheme was selected to effectivly transfer that 9600 BPS rate within a modulation envelope that stays within a 12.5 KHz channel.

A P25 receiver will receive the signal no matter what the assigned channel width (12.5 KHz or 25 kHz)

 

[nd5y]

I'm not a good technical writer so I hope people can understand this.
Regular (wide) FM (not FM broadcast) is supposed to be 5 kHz deviation and 16 or 20 KHz bandwidth.
Narrowband is 2.5 kHz deviation and 11.2 kHz bandwidth.
In a receiver, the IF filter bandwidth for wide FM is anywhere from
15 to 30 kHz for wide and 9 to 15 kHz for narrowband.
A high quality real 2-way radio might have selectivity of -80 dB at 25 kHz
and a cheap junk consumer grade radio like all current VHF/UHF
ham rigs and scanners with cheap IF filters might have maybe -50 dB at 30 kHz.

The short answer is you can still hear narrowband 2.5 kHz deviation analog
FM on any scanner. The receive audio will just be a lot lower and you will
have more interference from adjacent channels that are only 7.5 or 12.5 kHz away.

Tom ND5Y

 

[DaveNF2G]

The receive audio will just be a lot lower and you will
have more interference from adjacent channels that are only 7.5 or 12.5 kHz away.

In fact, traffic on the 7.5 kHz in-between channels will usually sound like it's exactly on the frequency you're monitoring except for weaker audio. Last night, one of the local police departments was using its new narrowband "tactical" channel and their traffic was loud and clear on the adjacent wideband fire channel.

73 de Dave, NF2G

 

[N_Jay]

The receive audio will just be a lot lower and you will
have more interference from adjacent channels that are only 7.5 or 12.5 kHz away.

In fact, traffic on the 7.5 kHz in-between channels will usually sound like it's exactly on the frequency you're monitoring except for weaker audio. Last night, one of the local police departments was using its new narrowband "tactical" channel and their traffic was loud and clear on the adjacent wideband fire channel.

73 de Dave, NF2G

Analog or Digital?

 

[Voyager]

Narrowband in simple terms:

Each "channel only uses 1/2 as much bandwidth, making room for more channels. Logically, 1/2 as much bandwidth used means twice as much available as before. Once everyone is narrowbanded, it effectivly doubles the number of available channels to be licensed.

Not quite. Let's define some industry standards first.

Wide FM = +/- 75 kHz deviation, or about 200 kHz bandwidth.
Standard FM = +/- 15 kHz deviation or about 40 kHz bandwidth.
NarrowBand FM = +/- 5 kHz deviation or about 16 kHz bandwidth.
SuperNarrow FM (AKA SNFM) = +/- 2.5 kHz deviation, or about 11 kHz bandwidth.

Of these four, Wide FM is used by FM and TV broadcast. (that's about it)

Standard FM is almost extinct, being used by a few hams as links and by the military.

NarrowBand FM is used by nearly everyone, and has been for the past 30+ years when the switch was made from standard FM to NarrowBand FM. There are even some transceivers out there marked "Converted to NarrowBand FM - 5 kHz".

SNFM started showing up a few years ago and is used on the new "7.5 kHz channels" on VHF (such as 155.1675 MHz), and on some 12.5 kHz splinter channels (as well asa few standard channels) on UHF. It is called narrowband FM by some manufacturers, but that does little but confuse most users - especially those in the industry and those who have been around when NBFM came into wide use in the 60s. It is unfortunate that one scanner manufacturer has chosen to use the term 'NFM' for what is really SNFM, and FM for what is NBFM, but everyone can see the confusion that is causing.

When the switch from FM (40 kHz BW) to NFM (15 kHz BW) was made in the 60s, it more than cut in half the bandwidth of every signal. As you can see, going from NBFM (16 kHz BW) to SNFM (11 kHz BW) does not yeild a doubling of the available frequencies per se. At best, it gives you nearly 1/3 more spectrum. Of course, the problem is that until all the users convert from NBFM to SNFM, NBFM users will greatly interfere with operations on SNFM channels.

Things are bad enough trying to use 16 kHz BW signals on 15 kHz BW channels. Many people know this listening to scanners and hearing strong adjacent signals blead over to the channel they are trying to monitor. But, they will be much worse when (or IF) the conversion is complete and people are using 11 kHz BW signals on 7.5 kHz BW channels. Someone does not know simple math at the FCC, I guess. :roll:

While I would agree with your " it effectivly doubles the number of available channels to be licensed" statement, since there will be (actually already ARE on VHF High Band) twice the number of channels available for licenses, it does NOT double the available spectrum. Someone is using 'new math' on the radio spectrum. As I have shown above, you will have about 1/3 more spectrum. The difference will be 'shared' between adjacent channel users in the form of adjacent channel interference.

Joe M.

 

[nmfire10]

Voyager, all of that may be true if you want to be pickey and over technical.

But in reality these days, and for what the subject of this thread is, in commercial two-way radio, there is "Wideband" and "Narrowband", end of story. Wideband is the 5Khz Deviation. Narrowband is 2.5Khz Deviation. Anything you buy today that uses the terms "wide" or "narrow" are refering to that.

I'm not saying your wrong, but in reality, it has really gone out the window.

 

[Voyager]

Voyager, all of that may be true if you want to be pickey and over technical.

Or the term I prefer... ACCURATE.

Funny. AOR uses the CORRECT, STANDARD terms - WFM for BC, NFM for NBFM, and SFM for SNFM. In fact, there is only one manufacturer who is promoting the NFM term for SNFM. AND MANY people are incorrectly setting up their scanners based on standard terms not realizing that their terminology is not the same as the rest of the world.

All you do when you promote this 'there is only wide and narrow' blubber is to advance the ignorance and misinformation.

In the commercial world, at least Motorola, there is no Wide and Narrow - the channels are set up based on the bandwidth of the signal (which is another accurate way of describing the differences).

As I said, I prefer using ACCURATE INDUSTRY STANDARDS. That's all. That way, everyone is on the same page. There should not be one set of standards for the industry and another for hobbyists. Doing that only makes hobbyists look stupid by using the wrong terms.

Joe M.

 

[N_Jay]

Voyager, all of that may be true if you want to be pickey and over technical.

Or the term I prefer... ACCURATE.

Joe M.

Picky or Accurate, it's a matter context.

Voyger certainly provided a lot of great information.

No reason to fault him for that.

As for whether Voyger is "out the window", all depends:

nmfire10, does your scanner have a wide and narrow FM mode?
If so what bandwidths does it refer to?
(You have the constitutional right not to answer, as you may incriminate yourself)
E.G.
"But in reality these days, and for what the subject of this thread is, in commercial two-way radio, there is "Wideband" and "Narrowband", end of story. Wideband is the 5Khz Deviation. Narrowband is 2.5Khz Deviation. Anything you buy today that uses the terms "wide" or "narrow" are refering to that."

 

[Voyager]

nmfire10, does your scanner have a wide and narrow FM mode?
If so what bandwidths does it refer to?
(You have the constitutional right not to answer, as you may incriminate yourself)

Or, more to the point: If someone asks if a PRO-96 will receive Wide FM, how do you answer? Wide FM as NM defines it, yes. Wide FM as most everyone else defines it, no. By Wide FM, how would you know (without specifying WHICH Wide FM he means) if he means Broadcast FM or the most common Land Mobile FM mode (NBFM)? As I said, promoting the 'new terms' only serves to add confusion and misinformation.

The BC296D receives both Wide FM AND Wide FM. :lol:
(or would that be "Wide FM" and "Really Wide FM", NM?)

Joe M.

 

[unitcharlie]

WITH APOLOGIES...

plz answer the question... if i have a pro 96 will i be able to receive the narrowband transmissions?

 

[Voyager]

WITH APOLOGIES...

plz answer the question... if i have a pro 96 will i be able to receive the narrowband transmissions?

The PRO-96 receives NBFM fine. Although it supports channel spacing for SNFM, it lacks the mode for SNFM, so transmissions using SNFM will sound a little weak (audio-wise) and will be subject to a lot of adjacent channel interference.

If you're wondering what NBFM and SNFM are, see above.

Does that answer your question?

Joe M.

 

[mrjon]

WITH APOLOGIES...

plz answer the question... if i have a pro 96 will i be able to receive the narrowband transmissions?

The PRO-96 receives NBFM fine. Although it supports channel spacing for SNFM, it lacks the mode for SNFM, so transmissions using SNFM will sound a little weak (audio-wise) and will be subject to a lot of adjacent channel interference.

If you're wondering what NBFM and SNFM are, see above.

Does that answer your question?

Joe M.

Note that this also applies to the Pro-95, for those of us still using those. (With the same caveats.)