Wide Vs Narrow Channel Spacing

[WRUQ758]

Channel spacing for the GMRS repeater & simplex channels is 25 Khz and 12.5 for FRS channels. I hear a lot of users with low audio and in many cases this may be from someone using a narrowband radio on an GMRS appropriate wideband repeater. I am a radio tech but will not get into a technical rant about the differences. Basically 25 Khz spacing gives you WAY better audio and range due to the bandwith. Radios like the Midland MXT-400 come with the correct spacing out of the box. In a nutshell if you buy commercial Kenwood, Motorola Etc repeaters, mobiles and portables make sure they are older "wideband" capable radios for GMRS use. Whoever programs your radios can tell in the software. This is great news for GMRS users because there is a glut of cheap wideband capable UHF radios out there cheap that cannot be used on narrowband spacing on regular business band. If the commercial radio or repeater you buy is 12.5 narrowband capable make SURE whoever programs it has the permission "key" to set it to 25 Khz. Do not use 12.5 KHz spacing on GMRS, enjoy the better audio and range benefits of our wideband "exception" under FCC Part 95.

My personal FAVORITES are Motorola Maxtrac, Radius M100, GM300, Ht-600, P-200, & Saber. These were some of the best radios ever built but require special software and an obsolete DOS computer and RIB to program. 

Here is a list: Motorola Narrowband Capable Radios (comsourcewireless.com)

[Lscott]

I’ve had good luck with Kenwood radios. Most allow programming for wide or narrow band FM. My typical GMRS carry radio is the TK-3170.

https://pdfs.kenwoodproducts.com/9/TK-2170&3170Brochure.pdf

[marcspaz]

2 hours ago, WRUQ758 said:

Channel spacing for the GMRS repeater & simplex channels is 25 Khz and 12.5 for FRS channels. I hear a lot of users with low audio and in many cases this may be from someone using a narrowband radio on an GMRS appropriate wideband repeater. I am a radio tech but will not get into a technical rant about the differences. Basically 25 Khz spacing gives you WAY better audio and range due to the bandwith. Radios like the Midland MXT-400 come with the correct spacing out of the box. In a nutshell if you buy commercial Kenwood, Motorola Etc repeaters, mobiles and portables make sure they are older "wideband" capable radios for GMRS use. Whoever programs your radios can tell in the software. This is great news for GMRS users because there is a glut of cheap wideband capable UHF radios out there cheap that cannot be used on narrowband spacing on regular business band. If the commercial radio or repeater you buy is 12.5 narrowband capable make SURE whoever programs it has the permission "key" to set it to 25 Khz. Do not use 12.5 KHz spacing on GMRS, enjoy the better audio and range benefits of our wideband "exception" under FCC Part 95.

My personal FAVORITES are Motorola Maxtrac, Radius M100, GM300, Ht-600, P-200, & Saber. These were some of the best radios ever built but require special software and an obsolete DOS computer and RIB to program. 

Here is a list: Motorola Narrowband Capable Radios (comsourcewireless.com)

 

 

I'm sure this will spark an argument... but I want to make a few corrections.  I'm not trying to pick on you... just want to put a tad more accurate info out there.  Like you... my post is not very technical... more of a general concept.

You are mistaken about wider signal having more range.  The opposite is true... narrow band has better range.  Wide has better audio fidelity.  Wide receivers have less usable sensitivity than narrow bandwidth receivers because the wider the receiver, the more it fills with the broad spectrum noise.  It then takes more desired received signal to pull the data out of the noise, reducing range per watt. This is why major manufactures collectively agreed, many decades ago, that 2.5 kHz bandwidth for SSB voice transmissions would be considered "normal" bandwidth. 

Also, the "bandwidth" and "channel spacing" are not the same. It looks like you may have mixed them up.  In real-world application, GMRS WFM (aka wide band) "channel spacing" is 25 kHz and the typical occupied bandwidth is 20 kHz.  The NFM (aka narrow band) channels are spaced 12.5 kHz and are typically 11 kHz occupied bandwidth.  I measured one of my radios moments before posting this. My radio on wide band is 19.3 KHz with 4.4KHz deviation and narrow band is 10.3 KHz with 3.5 KHz deviation (a little hot).

In laymen terms, the more bandwidth you use, the more data you can send.  The more data you send, the better the fidelity can be.  In GMRS voice, that data is your voice.  Therefore, on wide band, you can have better audio fidelity due to more information transmitted and received. The reason audio from a narrow band transmission has low audio on a wide band receiver is because the receiver is tuned in such a way that it is listening to a wider spectrum of radio than the transmitted signal, and it is expecting more deviation than provided for the voice.  The empty RF space is filled with random noise (same noise that reduces sensitivity / range) and the lack of deviation leads to lower audio levels.  You combine the two and it can sound like less than half the expected/normal audio levels.

The inverse is true when a narrow receiver hears a wide signal.  The receiver is only hearing about half the signal (making it sound lower in tone) and the over-deviation causes a loud audio level... sometimes sounding a little distorted. 

[nokones]

My GMRS radio club operates their repeaters on narrowband and my radio units are programmed accordingly. Also, I am able to monitor two nearby high elevation repeaters that operate on wideband channels. I'm monitoring the narrowband channel with a Motorola XTL5000 radio and the two wideband channels with a CCR/CCSD radio with two receivers as base station units.

Personally, I think the narrowband channel sounds a lot clearer than the wideband channels. I'm just not seeing what is all the fuss about the differences between the two subjects. The narrowband channels are a lot more efficient and should be used on GMRS.  If people are experiencing lower audio levels with their CCR/CCSDs than "Turn Up the Volume".

Also, I have several vintage(30+ years) Motorola radios that can operate on either narrowband or wideband channels and I just don't see the differences

[Guest]

I always understood the move from wide-band to narrow-band as means to eventually increase the availability of channels on a specific frequency band -> narrow band can "pack" more channels / more simultaneous communication events.

Based on that understanding, narrow band would be beneficial for all users.

However, the early (pre-revamping) bubble box radios might have had a hard time hitting the frequencies and needed tolerances (tuned and more expensive parts) of the narrow band.

If that is one of the reasons, narrow band relies on "better" technologt that now is available on GMRS. But our spectrum sharing sibling FRS is using "good enough but really cheap" technology that might just rely on wide band regulations ...

 

[BoxCar]

11 hours ago, marcspaz said:

 

 

I'm sure this will spark an argument... but I want to make a few corrections.  I'm not trying to pick on you... just want to put a tad more accurate info out there.  Like you... my post is not very technical... more of a general concept.

You are mistaken about wider signal having more range.  The opposite is true... narrow band has better range.  Wide has better audio fidelity.  Wide receivers have less usable sensitivity than narrow bandwidth receivers because the wider the receiver, the more it fills with the broad spectrum noise.  It then takes more desired received signal to pull the data out of the noise, reducing range per watt. This is why major manufactures collectively agreed, many decades ago, that 2.5 kHz bandwidth for SSB voice transmissions would be considered "normal" bandwidth. 

Also, the "bandwidth" and "channel spacing" are not the same. It looks like you may have mixed them up.  In real-world application, GMRS WFM (aka wide band) "channel spacing" is 25 kHz and the typical occupied bandwidth is 20 kHz.  The NFM (aka narrow band) channels are spaced 12.5 kHz and are typically 11 kHz occupied bandwidth.  I measured one of my radios moments before posting this. My radio on wide band is 19.3 KHz with 4.4KHz deviation and narrow band is 10.3 KHz with 3.5 KHz deviation (a little hot).

In laymen terms, the more bandwidth you use, the more data you can send.  The more data you send, the better the fidelity can be.  In GMRS voice, that data is your voice.  Therefore, on wide band, you can have better audio fidelity due to more information transmitted and received. The reason audio from a narrow band transmission has low audio on a wide band receiver is because the receiver is tuned in such a way that it is listening to a wider spectrum of radio than the transmitted signal, and it is expecting more deviation than provided for the voice.  The empty RF space is filled with random noise (same noise that reduces sensitivity / range) and the lack of deviation leads to lower audio levels.  You combine the two and it can sound like less than half the expected/normal audio levels.

The inverse is true when a narrow receiver hears a wide signal.  The receiver is only hearing about half the signal (making it sound lower in tone) and the over-deviation causes a loud audio level... sometimes sounding a little distorted. 

As a former frequency coordinator, I have to say "depends." Most of the coordination plots use the Longley-Rice algorithm and the predicted coverage area between wide and narrow band remains the same in most cases. Some coverage areas do increase while some decrease, the change being about 3%. As to the performance of a radio at the fringe of the coverage, it again depends on both the radio's specifications and any change to the coverage shift if any,

[marcspaz]

2 minutes ago, BoxCar said:

As a former frequency coordinator,

 

I don't know if you mentioned that before, but I didn't know. That's actually pretty cool. Folks who do that work save the community a ton of aggravation and arguing. 

[Guest]

1 minute ago, marcspaz said:

... Folks who do that work save the community a ton of aggravation and arguing. 

@marcspaz ... this will not keep us from finding other issues to be "sad ham" about !!!     

 

But I agree: @BoxCar thank you for having been involved in coordinating frequencies !!!

 

 

[WRUU653]

18 minutes ago, WRXD372 said:

But our spectrum sharing sibling FRS is using "good enough but really cheap" technology that might just rely on wide band regulations ...

FRS is narrow band though... I may not be fully understanding what you are trying to convey. My understanding is that wide/narrow band in this context isn't about channel spacing but rather the band width of the transmission within the channel spacing.

[Guest]

Just now, WRUU653 said:

...  My understanding is that wide/narrow band in this context isn't about channel spacing but rather the band width of the transmission within the channel spacing.

I understand the use of narrow band to (1) reduce interferences on neighboring frequencies and (2) allowing for an increase in spectrum use as usable frequencies / channels could be packed more closely to each other.

In short terms, GMRS channels should experience less interference / bleed from neighboring channels, in the long run, that could allow a more packed channel lineup (not going to happen because the new and old channels would not be compatible!)

My bottom line is that it takes better build technology (components with lover levels of tolerances all around) to efficiently use narrow-band.

If I may use cell phone technology as an analog: My first cell phone in 1994 (Mototola MicroTAC 7200) was an amazing device at a time when spectrum was less of an issue based on subscriber numbers. A device with that kind of radio technology might best be used as a wide spectrum jammer on current cell bands - Yes, I know that we moved to different frequencies and protocols - but my point is that the old radio might look like a brute force approach based on today's standards...

 

[WRUU653]

18 minutes ago, WRXD372 said:

I understand the use of narrow band to (1) reduce interferences on neighboring frequencies and (2) allowing for an increase in spectrum use as usable frequencies / channels could be packed more closely to each other.

In short terms, GMRS channels should experience less interference / bleed from neighboring channels, in the long run, that could allow a more packed channel lineup (not going to happen because the new and old channels would not be compatible!)

My bottom line is that it takes better build technology (components with lover levels of tolerances all around) to efficiently use narrow-band.

If I may use cell phone technology as an analog: My first cell phone in 1994 (Mototola MicroTAC 7200) was an amazing device at a time when spectrum was less of an issue based on subscriber numbers. A device with that kind of radio technology might best be used as a wide spectrum jammer on current cell bands - Yes, I know that we moved to different frequencies and protocols - but my point is that the old radio might look like a brute force approach based on today's standards...

 

Thanks,  I misunderstood and thought you were either saying FRS was wide or that narrow required better technology but I think you are saying better technology would be needed (which it isn't in todays FRS bubble packs and I'm sure other radios) if you utilized moving things closer together to reduce bleed over.  

I need more coffee 

[Guest]

12 minutes ago, WRUU653 said:

I need more coffee 

... maybe I should have some coffee before typing !

   

[marcspaz]

9 hours ago, nokones said:

If people are experiencing lower audio levels with their CCR/CCSDs than "Turn Up the Volume".

 

The problem with this is, when everyone else is using the same bandwidth and deviation, then my speakers rattle and my ears hurt from the volume blasting. Spending several minutes playing 'chase the volume level' is usually not a good time, prompting me to tell the operator what's happening or me just turning my radio off.

[WRUQ758]

I stand corrected Marc Spaz. Found this post (below) elsewhere. Eloquently explains how this relates to GMRS and I agree with this poster. Narrowband, P-25, DMR your private repeater. It will just lock out 99% of us who use Analog 25 KHz spacing. I would revel in the fact I can use the older radios with better audio. Anyone who thinks the Motorola XPR audio compares to a Maxtrac or Marartac - well.... Just my 2c

ALL Credit to "RFI-EMI-Guy"

"The nomenclature of 12.5 and 25 KHz channels has been somewhat confused to indicate operating bandwidth. The actual modulation bandwidth of an analog narrowband radio is about 11.25 KHz and a wideband radio about 16 KHz. The deviation is +/- 2.5 KHz for narrowband and +/- 5.0 KHz for wideband. The additional "channel" bandwidth accommodates the deviation, the voice modulation frequency (Carsons Rule), filter and frequency offset tolerances.

1) GMRS is under no mandate to narrow band and there is no great benefit to narrow band GMRS as the FRS channels were already allocated on the 12.5 KHz offsets. Because of the power differential the determination was that GMRS bandwidth would be unaffected.

2) No additional channels can be attained by narrow-banding GMRS.

3) There will be a 3 dB degradation going from analog "wide band" (25 KHz channel spacing) to narrow band 12.5 KHz. See the link below where, a table and maps will explain the interaction of reducing the modulation and using a narrower filter in the receiver. There is some receiver sensitivity improvement, however, lowering the deviation reduces the modulation energy.

4) If you operate narrow band radios and wish to roam to wide band channels and repeaters, your audio will be low and everyone else will be booming. The reverse is true if you operate a narrowband repeater, wideband roamers will be booming and your repeater audio will be weak to them".

[Lscott]

1 hour ago, WRUQ758 said:

There will be a 3 dB degradation going from analog "wide band" (25 KHz channel spacing) to narrow band 12.5 KHz. See the link below where, a table and maps will explain the interaction of reducing the modulation and using a narrower filter in the receiver. There is some receiver sensitivity improvement, however, lowering the deviation reduces the modulation energy.

It’s a bit more complex than the above.

 

Narrowband vs Wideband.pdf

[axorlov]

1 hour ago, Lscott said:

It’s a bit more complex than the above.

 

Narrowband vs Wideband.pdf 190.54 kB · 3 downloads

Great article, thanks. Explains real life vs theoretical +3db advantage of wideband.

[Lscott]

6 hours ago, axorlov said:

Great article, thanks. Explains real life vs theoretical +3db advantage of wideband.

This also explains why manufacturers went to digital for the very narrow band channel setting, 6.25KHz, which at some point the FCC might mandate. The manufacturers claim FM using anything less than the current 12.5KHz channel spacing isn’t practical and the only way to achieve it is through digital voice technologies.