Radio Certification and Occupied Bandwidth?

[Lscott]

I’ve been thinking about an issue, which isn’t important at the moment, where the occupied bandwidth of the signal is a major concern. The FCC spec’s 20K0FE3 as the normal “wide-band” FM signal mode for GMRS. However many people, including myself, have Part 95 certified commercial radios that are spec’ed for 16K0FE3, the old Part 90 rules, we use. Also the vast majority of GMRS repeaters are built using commercial Part 90 gear, which has the slightly narrower emission. Likely wouldn’t even notice the differences on the air. 
 

So the question is are the typical radios being specifically manufactured for GMRS are they certified for 20KHz or 16KHz occupied bandwidth? If the later it may make a difference for future proposed changes to the service. Just one less item for the FCC to raise objections over since it helps reduce the interference potential from adjacent channels.

[KAF6045]

If you look, you will also find the narrowband (FRS interstitials) often show up as 11Kxxx for a 12.5K channel. Also note that the original GMRS primary channels were on 25K spacing, even if only allowed 20K bandwidth.

The interstitials complicate matters, as they fall midway between each primary (so have a 25K spacing, but are only 12.5K from the center of each primary). Use of 16Kxxx is probably a compromise to avoid too much bleed over into adjacent channels.

[Lscott]

I think that’s why the FCC left the spec’s for the interstitial channels between the repeater main ones at 11K0F3E and 0.5 watts to limit the interference to them.

I’m just wondering if the manufacturers are leaving the bandwidth at 16K0F3E on the higher power channels since many of the Chinese GMRS radios are based on either old Part 90 or Ham gear with tweaked firmware to make it legal for Part 95. 

If the norm for the majority of the radios in use is 16K0F3E the FCC could just tweak the rules and make it official. That leaves a larger guard band between channels that could be employed to advantage for other uses.

[axorlov]

I never saw a radio certified for 20K0F3E for Part 90. It does not mean they do not exist, I just never stumbled upon any of such things. The radios I'm aware off are 16K0 for wide band and 11K0 or 10K0 for narrow band. And there are Baofengs that are certified for 5K0, laughable. Narrow-narrow band.

[Lscott]

I was concerned with GMRS specifically. Many of the popular radios I suspected are firmware tweaked versions of the commercial LMR versions. I found a list of some of the popular models for GMRS with their FCC ID's here.

https://www.buytwowayradios.com/blog/2018/12/wouxun-radio-fcc-id-and-type-acceptance-chart.html

Doing a spot check of the GMRS certified radios the ones I looked at are all 16K0F3E. That's sort of what I expected.