GMRS Band Width

[WRZM243]

Narrow or Wide Band Width During Operation?

[Lscott]

The attached paper was published in an engineering journal. It goes a bit more into the details of narrow verses wide band FM. The material isn't for the "casual" reader.

Narrowband vs Wideband.pdf

[OffRoaderX]

GMRS is primarily Wideband except for channels 8-14. 

[WSAA635]

Also if you listen to a narrow band channel set to wide band it'll sound fine but if you try to listen to a wide band channel while set to narrow band it'll sound wrong.

[nokones]

It appears that 99.9% of the GMRS repeaters throughout the country operate on wideband channels. The only exception to the norm is the Arizona GMRS Repeater Club which operates all four of their repeaters, and nine tactical channels on narrowband channels and without any issues in regards to audio quality.

Personally, I would like to see the FCC mandate that the GMRS channel operate on narrowband channels. If it works for Part 90 radio services it can work for Part 95 radio services.

Narrowband emissions help facilitate spectrum efficiency and minimize adjacent channel interference.

[WRQC527]

21 hours ago, WRZM243 said:

Narrow or Wide Band Width During Operation?

If you want to operate strictly by FCC bandwidth regulations, refer to this link:

https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E/section-95.1773

Everything you want to know about regulations for personal radio services can be found by following this link:

https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95

 

[Lscott]

On 2/12/2024 at 6:29 AM, nokones said:

Personally, I would like to see the FCC mandate that the GMRS channel operate on narrowband channels. If it works for Part 90 radio services it can work for Part 95 radio services.

Narrowband emissions help facilitate spectrum efficiency and minimize adjacent channel interference.

The narrow band won't help with spectrum efficiency unless the FCC was going to add more channels to GMRS, which likely won't happen.

The channel interference part is beneficial. There are some interstitial channels that can cause interference to the adjacent main channels. If all of the channels were made narrow band the guard band between them would be greater.

The down side to narrow band is the range reduction. Many Part 90 users found that out quickly when the FCC mandated narrow band for that service group.

Be careful what you wish for.

[nokones]

After the system I was involved with during the narrowband changeover, we did not have any issues as most have described with their experiences. All of our systems were designed with overlapping coverage for redundancy with simulcast, and voting receivers. There could have been some propagation differences but it didn't impact operations.

Even the difference in the audio quality was negligible. I guess when you use quality radios you don't experience those issues.

[Lscott]

1 hour ago, nokones said:

After the system I was involved with during the narrowband changeover, we did not have any issues as most have described with their experiences. All of our systems were designed with overlapping coverage for redundancy with simulcast, and voting receivers. There could have been some propagation differences but it didn't impact operations.

Even the difference in the audio quality was negligible. I guess when you use quality radios you don't experience those issues.

Those people were lucky. Several posts in other forum sites users reported noticeable reduction in range. I guess it all depended on the original system design before the changes.

[gortex2]

I run all 6 of my repeaters in narrow band. As said a true built out repeater will not work better or worse than a wideband. I'm sure someone will jump on and give us data to prove different but thousands of systems are narrowband and work just fine. All our SAR stuff went from wideband to narrow and did not loose coverage that was noticable to the end user. Anyway yes most GMRS is wideband but there are narrowband repeates out there.