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Author Topic: Narrowband vs Wideband FM  (Read 8975 times)
K6AER
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« on: March 01, 2007, 06:51:37 PM »

The new APCO standard for FM is Narrow Band +/-2.5 KHz. For amateur use set the radio to Wide Band +/- 5 KHz.
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KG4YTL
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« Reply #1 on: March 01, 2007, 01:58:37 PM »

I have an option of narrowband or wideband FM on my VHF handheld (VX-150).  Which one is the standard in the 2m world?  If I switch to the nonstandard one, what happens?
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KX8N
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« Reply #2 on: March 01, 2007, 02:15:32 PM »

I don't have that radio, but I'm sure it only transmits narrowband.  Narrowband is what hams use, as well as emergency services, police, school buses, old cordless phones, etc.  Wideband is for commercial broadcasts, such as your local music or talk radio station.

It won't matter what you have it set on for transmit.  However, if it's set on wideband, I don't think you will actually hear the narrowband signal if somebody comes back to you.  If you have it set for narrowband and listen to a wideband signal, I think you get some noise or something, but you can't really discern what you are listening to.
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N3OX
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« Reply #3 on: March 01, 2007, 02:40:53 PM »

Wide FM is for listening to the FM broadcast band..
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KE4FBP
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« Reply #4 on: March 01, 2007, 03:41:45 PM »

I believe the gentlemen who have posted responses are not familiar with the emerging narrow deviation of the latest commercial/public service/military and most recently ham VHF/UHF transcievers.

The default setting on your radio is "Wide" See page 37 of your manual (SET item #33). I believe this is the setting that will work with most ham repeaters and most other ham transcievers.

The narrow setting is likely for Narrow Deviation - which is probably half the deviation traditionally used on the ham VHF bands. The Narrow Deviation setting allows closer channel spacing on public service bands. I don't know if it is used yet in congested areas of the country for any ham repeaters.

I don't know if MARS uses any VHF frequencies, but the military unit in which I serve recently had VHF frequencies reassigned; and, the specified deviation was changed from 'wide' to 'narrow'.

There may be parts of the world where hams are greatly restricted in the VHF bands. Having narrow deviation will allow more people to operate in the same spectrum space.

I think the wide deviation setting on your VX-150 is about 5KHz and the narrow deviation setting is 2.5Khz. Broadcast band deviation for FM music in stereo is 75KHz, requiring 200KHz channel spacing.

Hope this info helps. And, if I'm wrong please let me know.
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N3OX
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« Reply #5 on: March 01, 2007, 07:22:16 PM »

"I believe the gentlemen who have posted responses are not familiar with the emerging narrow deviation of the latest commercial/public service/military and most recently ham VHF/UHF transcievers."

Yep, sorry about that... the Wide FM (WFM) in my FT-857D is for listening to FM broadcast.

Turns out the '857 also has two FM transmission/reception modes... normal and narrow (FM and FMN)



Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
K8ZO
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« Reply #6 on: March 01, 2007, 07:43:06 PM »

Icom recommends the narrow setting for 15khz split repeaters, if I remember correctly.
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DA2KI
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« Reply #7 on: March 02, 2007, 02:25:55 PM »

The new Land Mobile Radio standards of "wideband" vs "narrowband" refer to the bandwidth of the signal.  Older analog wideband FM business band signals are 25 kHz wide.  The new mandated narrowband signals are only 12.5 kHz wide.  Most manufacturers are achieving this reduced signal bandwidth by using digital operation.  While the reduction in occupied bandwidth requires a reduction in deviation, the focus is on the bandwidth.
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W8JI
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« Reply #8 on: March 02, 2007, 04:50:19 PM »

I'd read the manual of your rig carefully. There are really several values of FM deviation in common use.

The standard for narrow band amateur FM is 5kHz deviation. Virtually all repeaters are narrow band 5kHz deviation.

Commercial two-way FM now has different standards. In the 60's everything was wideband FM with 15 kHz deviation. Amateurs also used wideband FM with 15kHz deviation. By 1975 or so it was almost all narrow band at 5kHz.

Commercial rigs are now subject to even narrower narrow FM. It is often called super or ultra narrow band FM and has a peak deviation of 2.5kHz, half of a normal narrow band FM.

FM BC is 75kHz deviation.

What happens is this:

If you use wideband FM..any audio from narrow band FM sounds weak and the signal gets noisy fast. Wide FM has less range for a give signal level at the antenna. When you transmit you will chop out on audio peaks and sound very distorted on a narrow receiver.

If you use narrow FM on a wide FM system, your transmit audio will sound weak. Your receiver will chop or squelch up on audio peaks from the wide transmitter, or sound very distorted on peaks.

Just read the manual to be sure they aren't calling super or ultra narrow (2.5kHz deviation) narrow, and regular narrow (5kHz) wide. Real two way wide is 15kHz, real FM BC wide is 75kHz, real amateur wide is 15kHz, real amateur narrow is 5kHz. Some commercial rigs are now calling super FM narrow (2.5kHz) narrow and 5kHz standard narrow.

Confused? You should be. That's why you have to read the manual and see what the manufacturer of YOUR rig calls narrow and wide. Virtually ALL amateur communications is narrow FM, with 5kHz deviation.

73 Tom



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KB1LKR
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« Reply #9 on: March 02, 2007, 06:58:08 PM »

Believe the VX-150 is the same as the FT-60r 5 kHz wideband, 2.5kHz narrow. 5 kHz is the current standard for 2m use.

Not that it matters for this (or the FT-60r), but FRS and GMRS use 2.5 kHz.

As noted above "wide" is context sensitive -- FM broadcast band (or analog broadcast TV audio) is truely WIDE, but 2m, 1.25m or 70 cm amateur is wide relative to FRS/GMRS for example.
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KD4KGI
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« Reply #10 on: May 02, 2007, 12:11:12 AM »

Since Narrowband FM takes up less bandwidth, would it be advisable to use this for simplex communications between 2 stations for greater distances? Will this punch through a bit better,but with less sound quality, kind of like switching from AM to SSB?
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