Narrow Band vs. Wide Band

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Gatorman

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Can someone explain to me, in layman's terms, what the difference is between the new NB FM vs. the old WBFM in terms of listening on an older scanner? Is the modulation scheme different? I'm talking about an analog signal at this point.
 

n4yek

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Gatorman said:
Can someone explain to me, in layman's terms, what the difference is between the new NB FM vs. the old WBFM in terms of listening on an older scanner? Is the modulation scheme different? I'm talking about an analog signal at this point.
Wide band FM is what your car radio, home stereo, and brodcast tv audio is,
Narrow band FM is what you listen to on your scanner; Police, Fire, City Services, etc... (has always been narrow band, just not called narrow band a whole lot until recent years)
 
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Gatorman

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I don't think that is what I'm looking for.......

Leave FM broadcast out of it. Right now and in the past, the FM land mobile stuff was spaced a certain distance apart. Typical freq was 155.370, .375, etc. Now, to make more use of the spectrum, they are spacing the freqs much closer, 155.3775, etc. I know, in years past, land mobile was called narrow-band FM. Maybe this stuff should be called narrow/narrow-band FM. Also, will it be analog or only P25?????

This is what I'm trying to determine.

Thanks
 

kf4lhp

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You can run analog or digital on narrowband frequencies. The only difference I've noticed on narrowband frequencies is that they are a bit lower volume due to there being less bandwidth to be modulated.
 

Gatorman

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Thanks

Matthew, thanks very much. That is what I was looking for. The only NB channels around here are P25. Just curious what analog sounded like. I know that Motorola is selling radios like hot cakes that are NB and give the operator TWO channels on one NB frequency. I have used them. They are digital and unfortunately NOT P25. So, there is no way to listen to them. You will hear a buzz saw on your scanner that is very annoying if you encounter one of these systems. They are VHF and UHF, conventional, not trunking.
 

whitstu

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That new system Motorola is trying to sell is called TRBO. It is TDMA (Time Division Multiple Access) based modulation scheme. It is similar to IDEN/Nextel/SouthernLinc. What TDMA does is it allows 2 Time Slots on one Narrow Band frequency. For instance if you had one frequency you could have 2 people talking at the same time, on different timeslots of course. It also allows for Encryption, GPS data, and Text Messages to be sent over the air. I think you may be able to attach a IP address to all subscriber units as well, but I'm not sure. Kenwood also has a system like this and they are calling it the NEXEDGE series and it capable of being trunked or so i read.
 

rcbarry

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When my local digital trunking system (Burlington County NJ APCO 25) goes to the narrow band, how will it effect the use of scanners.I have been asked by the local fire dept to gather research on the effect it will have on scanning prior to them purchasing new scanners for the station and the command vehicles. As we understand it, all of our department radios must be on the narrow band by 2013 so we want to be sure to make a purchase that will last well into the change.
 
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When my local digital trunking system (Burlington County NJ APCO 25) goes to the narrow band, how will it effect the use of scanners.I have been asked by the local fire dept to gather research on the effect it will have on scanning prior to them purchasing new scanners for the station and the command vehicles. As we understand it, all of our department radios must be on the narrow band by 2013 so we want to be sure to make a purchase that will last well into the change.

As far as how narrowband effects scanners, This is what I can tell you, So hopefully it helps you out.

If you've got a scanner that doesn't do narrow-band, It'll just round of the frequencies, and for the most part, you'll recieve it all the same, But from what I've found, if it's a distant/weak signal, You'll hear it better if you're actually using a scanner that does the true narrrow-band frequency, Especially if you've got it toned squelched.

I'm also 99% Certain that all digital trunking scanners can also do narrow-band VHF, So As long as you have scanners that can do the current system, You shold be fine when it goes narrow-band VHF, Although I'm not exactly sure how VHF APCO trunking works exactly, Because I have never done it.
 

n5ims

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My experience is this (please note that this is a very simplified explaination and may not be 100% technically correct):

Listening to a wide band FM signal with a narrow band FM receiver (or conversly a narrow band FM signal with a wide band FM receiver), you may experience lower or higher than normal volume and/or some audio distortion. You most often will still be able to hear the conversation, however.

If your receiver is wide band FM and the frequency step size doesn't allow you to enter the additional narrow band channels (e.g. it only goes in steps of 25, and you can't directly tune the 12.5 stepped channels), you may not be able to directly tune the desired channel, this often isn't an issue, but can cause problems if the signal is weak or there are strong signals on adjacent frequencies.
 
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N_Jay

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Can someone explain to me, in layman's terms, what the difference is between the new NB FM vs. the old WBFM in terms of listening on an older scanner? Is the modulation scheme different? I'm talking about an analog signal at this point.
Well, I would have to say, that given this clear and well written question, I would be confused if I tried to learn the answer from this thread. :wink:

So since you are asking about "The new NB FM" with regard to scanners, we will not need to go into any discussion on true wideband FM and used in broadcast FM and the audio channel of analog TV. Nor do we need to confuse the discussion with the technical definition of WBFM vs. NBFM as it is irrelevant to the question.

For this discussion we will consider WBFM as the mode used as the standard for the land mobile industry for most of the last 40 to 50 years.

We will likewise consider NBFM to be the mode used in the land mobile industry, starting in limited applications about 20 years ago, spreading to fairly common use over the last 10 years, and becoming the standard requirement over the next couple of years.

Since you asked specifically about analog, we will stay with FM as used by the land mobile industry and not add all the confusion added by trying to mix a discussion about digital into the answer.

So here is the simple answer to your clear question. It is not a simple subject, so please read though this answer at least twice carefully.

There are two interrelated pieces you need to understand. Sometimes it is easier to do visually than with a narrative, so grab some scrap paper and start drawing.

Channel spacing. Think of the spectrum as a lone and channel centers as tick marks on the line. The ticks are channel center frequencies, and the space between the ticks is the channel spacing.

Channel bandwidth is the size of the "Lump" of information placed on the channel.

WBFM typically used a channel spacing of 25 to 30 KHz to place channels that occupy about 20 KHz of signal. (These are generated with +/-5 kHz FM modulation)

NBFM typically used a channel spacing of 12.5 to 15 KHz to place channels that occupy about 11 KHz of signal. (These are generated with +/-2.5 kHz FM modulation)

So if a WBFM receiver is trying to listen to a NBFM signal the sound will be relatively soft, and you may here the adjacent channel (If one is there).

If a NBFM receiver is trying to listen to a WBFM signal the sound will be relatively loud and may be distorted since some of the signal may go beyond the "window" the receiver is designed to receive.

Now we get another level of confusion, because your scanner is designed to be able to tune the channels it was designed to receive so it has a certain channel step size. It may seem to be a continuous tuning receiver, but in fact it can only tune to specific frequencies.

If the world was perfect that step size would only have to match up with the channel spacing for the band you are in, but history has screwed that up.

Over time channels have been spaced at both 25 and 30 kHz spacing on certain bands, and over time channels have been assigned on the lines between the normal channel spacing positions. For this reason scanners are designed with various (but minimized) channel step sizes.
With the move to narrowband, and therefore the creation of additional channel positions (tick-marks) many new channels may not fall onto the step positions of a scanner designed only for WBFM use.

In general if you can get the receiver to a frequency "within" the signal, it will receive the signal. so if your scanner will not go exactly to the channel center it may not be a significant problem. (much like listening to a NBFM signal with a WBFM receiver.

I hope this helps.
 

rcbarry

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So than as I understand it, even my old pro2096 would still be useable. Is there a certain scanner that I should be looking at knowing that I will be purchasing 2 to 5 scanners that will be mounted in the command vehicles at our fire department?

Is there a trunked narrow band in use in the Delran, NJ area that I can experiment with?

Bob
 

milf

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Your 2096 will work fine on phase 1 of the narrowbanding. When VHF goes to 12.5 spacing. When Phase 2 happens and the bandwidth is tightened to 6.25, all VHF will have to go digital. That is the only way to make that tight of spacing work. If current P-25 (FDMA) digital is used then your current gen scanners will still work. But if they do make the change to P-25 Phase 2 (TDMA) then youll have to wait til the scanner industry releases an TDMA capable scanner. The changes to the 6.25 and TDMA are still a few years away. So don't panic and have fun.
Example-
FM spacing... 155.3100, 155.3250...
Phase 1 NFM... 155.3100, 155.3175, 155.3225
Phase 2 NFM... 155.31025, 155.31250 etc

More usable spots on the band... Once you add TDMA you then also get...
155.6125 A 155.6125 B Two chans per a freq. This will especially be useful in trunking as youll double the amount of available loading.. Where a current TRS with say 5 freqs has one CC, and the other freqs can all be used for CW, Voice, and data, allowing only 4 different TG's to be on the same site at the same time, with TDMA youll now have one freq as CC and voice, and the other four giving you now eight open slots, for up to nine TG's at once on the same site.
 
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N_Jay

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Your 2096 will work fine on phase 1 of the narrowbanding. When VHF goes to 12.5 spacing. When Phase 2 happens and the bandwidth is tightened to 6.25, all VHF will have to go digital. That is the only way to make that tight of spacing work. If current P-25 (FDMA) digital is used then your current gen scanners will still work. But if they do make the change to P-25 Phase 2 (TDMA) then youll have to wait til the scanner industry releases an TDMA capable scanner. The changes to the 6.25 and TDMA are still a few years away. So don't panic and have fun.
Example-
FM spacing... 155.3100, 155.3250...
Phase 1 NFM... 155.3100, 155.3175, 155.3225
Phase 2 NFM... 155.31025, 155.31250 etc

More usable spots on the band... Once you add TDMA you then also get...
155.6125 A 155.6125 B Two chans per a freq. This will especially be useful in trunking as youll double the amount of available loading.. Where a current TRS with say 5 freqs has one CC, and the other freqs can all be used for CW, Voice, and data, allowing only 4 different TG's to be on the same site at the same time, with TDMA youll now have one freq as CC and voice, and the other four giving you now eight open slots, for up to nine TG's at once on the same site.
OUCH!!!!!!!!!!!!!!!

P25 Phase 2 operates on 12.5 kHz channels, and has NOTHING to do with narrowbanding to 6.25 kHz channels (other than meeting the FCC efficiency requirement).

Since the question was on narrowbanding ANALOG, I did not bother with all the errors building up in the OFF-TOPIC digital discussion.

Maybe that is needed also?
 

rcbarry

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I guess I wasnt very clear. We do operate on a digital trunked APCO 25 system (Motorola) in the 500 MHZ band. We also have low power 500 MHZ non trunked analog ops channels and a back up system known as WAR Channels (Wide Areaa Repeater) that are also analog, high power in the 500 MHZ. It is our intention to keep this same set up, but of course go narrow to stay leagal.

We need to replace our station scanners and the scanners in the command cars are slso in the need of replacement. With the price of digital scanners it would be prudent to purchase scanners that will be good after we go narrow.

What I need to know is what effect will the change over have on the presant day digital scanners, do we need to wait for new scanner techno to be released to get what we need. Does anyone have a scanner to recomed for the job.
 
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N_Jay

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I would think that any scanner out today for Digital (P25 Phase1) will do P25 Phase 1, analog WBFM (25 kHz) and analog NBFM (12.5 kHz) just fine.

I would think that any scanner made in the last few years, even if not digital, will do analog WBFM (25 kHz) and analog NBFM (12.5 kHz). But I would double check the specific models.

There will probably not be any 6.25 kHz analog to worry about.

NOTHING that is out now, or coming soon is going to do P25 Phase 2, Motorola's pre-phase 2 TDMA, MotoTRBO, NXDN, iDEN, ProVoice, OpenSky or TETRA. (Of course, I could be surprised, but an not expecting to be).

I doubt anything will be upgradeable to these either, but someone could get tricky.
 

ButchGone

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Aren't the federal mandates to "go narrow band" for frequencies 512MHz and below? That's what I understand, but please correct if I am mistaken. Is this also the reason why there's a push to 700Mhz and/or 800Mhz since there is no requirement to go into 6.26Khz slots that high up the ladder? Is this also why 800Mhz trunked systems, analog and digital, won't have to worry about narrow banding?
BG..
 
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N_Jay

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Aren't the federal mandates to "go narrow band" for frequencies 512MHz and below?
Yes, by Jan 1 2013

That's what I understand, but please correct if I am mistaken.
So far, so good.

Is this also the reason why there's a push to 700Mhz and/or 800Mhz since there is no requirement to go into 6.26Khz slots that high up the ladder?
First, other than 700 MHz there is NO REQUIREMENT for 6.25 kHz operation.
Not directly.
The "push" for the higher bands is because that is where more open "greenfield" spectrum is located.
Additionally those bands are more friendly for trunking and other newer technologies.
The apparent push comes from the fact that many systems have to go through an almost complete replacement to be narrow banded, so for not much more they can move to a new band and get a whole new system without many of the issues of the lower bands, or having to deal with transitioning a live system.

Is this also why 800Mhz trunked systems, analog and digital, won't have to worry about narrow banding?
The reason they don't have to worry about it (yet) is because the FCC has not got around to making them.
Give it a few years (at least until the 800 MHz re-banding is done).
 

perry211

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Narrow Banding

Someone ask for a simple answer. Without changing frequencies or talking about steps.
(It's like putting 4 lanes of traffic on a 2 lane road.) Thats what the FCC wanted because it takes up less space in the radio world when you use less bandwith to do the same job. If your area goes to narrow band you may find the person in charge has changed the PL-Tones so don't think that your scanner has stopped working, It's just needs the new info. Or U may not use pl-tone and hear that morris code id all of the time.
In my case on my Kenwood TM-281a I just went into the programming software and clicked the narrow band block for one system. As another person has stated if they stay on the same freq and don't change tones, You will just hear them at apx. half volume. On my scanner I had to check the narrow band block and get the new PL-Tone to hear F&Rescue on the VHF crosspatch. All questions are good ones. :)
 

kayn1n32008

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You do realize this thread is almost 2 years old??
 
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