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GMRS / FRS Discussions related to GMRS (General Mobile Radio Service) and FRS (Family Radio Service) communications

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  #1 (permalink)  
Old 02-15-2010, 3:04 PM
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Default GMRS wide band or narrow band

Hello,

Can anyone tell me under which band can I expect to get the best range from. Using for example 462.575 on 25.0khz or 12.5khz. Does using wide band or narrow band affect your radio range?

Thanks!!
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Old 02-15-2010, 3:06 PM
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All else being the same 25 KHz should give you 1.5 to 6 db improved signal to noise (range)
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Old 02-15-2010, 10:42 PM
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All else being the same 25 KHz should give you 1.5 to 6 db improved signal to noise (range)
Am I the only one confused by this answer?
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Old 02-15-2010, 11:24 PM
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Originally Posted by conve36 View Post
Am I the only one confused by this answer?
Probably not.

Do you have a specific question?
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Old 02-16-2010, 1:22 AM
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All else being the same 25 KHz should give you 1.5 to 6 db improved signal to noise (range)

Am I the only one confused by this answer?
Cutting the modulation limiting diode in a CB (am) radio yields about the same sort of effect. The signal can be detected over high noise levels.

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Old 02-16-2010, 7:48 AM
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Cutting the modulation limiting diode in a CB (am) radio yields about the same sort of effect. The signal can be detected over high noise levels.

Bob
Yes, I guess it does if you don't consider the differences between AM and FM modulation.
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Old 02-16-2010, 7:33 PM
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Yes, I guess it does if you don't consider the differences between AM and FM modulation.
Perhaps I should have included the phrase: "In lay terms."

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Old 10-17-2012, 6:40 AM
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Hello.

Narrow banding is just that, putting a signal in a narrower "channel".
All things being equal, a 25kHz wide signal will have better coverage.
And, clipping the modulation limiting diode in a CB can easily cause over modulation, a louder signal but less range.
In AM the ideal is around 80 to 90% modulation.
Anything over and the signal splatters.
But if we reduce the carrier and part of one sideband we have a signal that has all the components of a regular AM signal but far greater range.
From a range standpoint, CW is king with SSB being next and VSRC being next in line and than a tossup between AM and FM.
The big advantage FM has is the reduction of static noise.
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Old 10-17-2012, 8:55 AM
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Quote:
Originally Posted by matt131 View Post
Hello,

Can anyone tell me under which band can I expect to get the best range from. Using for example 462.575 on 25.0khz or 12.5khz. Does using wide band or narrow band affect your radio range?

Thanks!!
Keep it wide band. You are not required to be narrow at this point, and your "coverage" will be better for the reasons others have explained above.

I am working on a project for my company modifying licenses and upgrading mobiles and MTR2000 repeaters to narrow. We expect a little less coverage, but given that we have Aux receivers, an extremely awesome main TX/RX site and a license for 300 watts / 500 ERP on VHF....I am going to have a hard time being able to tell if there is any difference. Mostly because I have no baseline. They haven't used this system for much besides data for a few years, but now the data has gone Cellular, and we are going to use the system for secondary/emergency backup on voice again. Our license is for 75mi radius....I have been told on 100 watts this thing was heard 150 miles out. I don't think I will have any range issues.

Not that you needed to know all that....but just to say that in a large system it may make no noticeable range difference to the end users with good equipment. Now, on the other hand, I operate 2 low profile 50 watt GMRS repeaters, and I can see where narrow banding them would reduce my range, especially with portables. If GMRS ever has to narrow band, I am just going to get a commercial license for my needs, and put up a TRBO repeater at a better site.
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Old 04-05-2013, 2:53 PM
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When we typically say "wide" band, it means 25khz right?

While GMRS frequencies are 25khz apart, the NEAREST assigned frequencies to GMRS are 12.5khz apart?

So would that make GMRS narrowband already?

For example
FRS CH 1 462.5625
GMRS CH 2 462.575
FRS CH 2 462.5875

Last edited by N2MRG; 04-05-2013 at 3:18 PM..
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Old 04-05-2013, 3:26 PM
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Here's the simple answer. Wideband is better. A wideband signal has up to 5 khz of deviation, while a narrowband signal can have no more than 2.5 khz deviation. GMRS is wideband, while FRS is narrowband. That's as simple as it gets.
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Old 04-05-2013, 3:39 PM
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ok that makes a bit more sense.

I noticed the PowerWerx GU-16 (part 95 radio) only allows programming Narrow band, which is why I was curious.
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Old 04-06-2013, 1:31 PM
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Ok I just got back into GMRS, and Im learning about the narrowband and other rules, my question is I have several FRS/GMRS bubble pack but expensive radios and they are WIDEBAND , how the FCC is going to regulate all those millions of GMRS radios already sold with wideband?

Im setting up a portable repeater to wideband because my bubble pack gmrs radios that are repeater capable will not work on narrowband with my repeater.
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Old 04-06-2013, 1:43 PM
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GMRS is a Part 95 service and not subject to the Part 90 narrow banding mandate.
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Old 04-06-2013, 10:02 PM
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Quote:
Originally Posted by cdesigns View Post
Ok I just got back into GMRS, and Im learning about the narrowband and other rules, my question is I have several FRS/GMRS bubble pack but expensive radios and they are WIDEBAND , how the FCC is going to regulate all those millions of GMRS radios already sold with wideband?

Im setting up a portable repeater to wideband because my bubble pack gmrs radios that are repeater capable will not work on narrowband with my repeater.
As Hooten just said, narrowbanding does not apply to GMRS. It also does not apply to hams, marine radio, NOAA weather broadcasts, the VHF paging channels, the UHF T-band, and MURS channels 4 and 5. Otherwise if you're a Part 90 licensee you must go to narrowband.

Last edited by W2NJS; 04-06-2013 at 10:06 PM..
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Old 04-06-2013, 10:49 PM
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Default GMRS wide band or narrow band

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Originally Posted by jhooten View Post
GMRS is a Part 95 service and not subject to the Part 90 narrow banding mandate.
How many times does this need to be said?


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Old 04-07-2013, 5:32 PM
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Where does the 1.5 to 6dB come from? If the receiver IF BW is reduced proportionally for narrow band you will improve the S/N by 3dB in narrow band mode and range will be improved in narrow band.

Any time you reduce receiver IF BW you get this improvement and going from say a typical 15KHz IF BW on FM to 1.5KHz (narrow SSB or wide CW) will give you a 10dB S/N improvement, not counting any change in mode. Going four times narrower to 375Hz BW for CW will give you a whopping 16dB S/N improvement over the original 15KHz starting point.
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Quote:
Originally Posted by N_Jay View Post
All else being the same 25 KHz should give you 1.5 to 6 db improved signal to noise (range)
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Old 04-08-2013, 3:24 PM
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It doesn't quite work that way. Your are mixing AM-FM-SSB-CW assuming they work the same. In an FM signal noise is noise is noise no matter what the IF bandwidth. As you narrow the signal the bandwidth decreases decreasing the signal to noise ratio reducing the received audio. Thus in FM reducing the bandwidth will reduce recovered audio in turn reducing the range from about 5 to 15% depending your conversion from db to percent. In our experience it seems to be about 10 to 20%.
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