A little bit more on the NB topic.
Back in the go-go 90's FM radio systems by and large operated at 5KHz deviation or a 25k bandwidth (business, public safety, amateur radio, etc) until "we ran out of spectrum", so the FCC decided we should all cut our deviation in half to ease the congestion. By 2013 everything* under part 90 operation (business, public safety, govt) that operates from 136 - 470 MHz must operate at a deviation of no more then 2.5k (12.5k bandwidth) This is what is commonly called "Narrow Band". The NTIA frequencies (federal government) has been operating NB for several years. Amateur Radio as well as CB / GMRS is not regulated under part 90, and is thus not required to narrow band.
Recently the "T-band" (470-520MHz) got a temporary exemption while congress pulls it's head out of it's ass, but that's another issue...
The FCC mandate, DOES NOT
require public safety to "go digital" although many agencies took advantage of federal grant money and decided to go digital when they bought new narrow band equipment.
Another huge misconception with narrow banding regards channel spacing. Back in the good old days radios operated on multiples of 12.5k or 5k channel steps, this has nothing to do with a 12.5k bandwidth,
so pay attention and don't get all confused like 90% of the people out there.
In California for years we have used 3 frequencies for Mutual Aid
You will notice these frequencies are spaced .015Mhz or 15KHz apart. The FCC has decided since we are going to be operating narrow band why not add "interstitial" frequencies in between these older ones, so now where there were three channels their can now be six!
So now we now have...
Most older radios and amateur radios will only operate in 30/25/15/12.5/5KHz channel spaces. You will notice that the first and third italicized frequencies is not divisible by 12.5KHz or 5KHz. (154272.5/12.5=12341.8
) so many old radios that are part 90 approved, and will do the 12.5k Narrow Band will not be able to accept these new frequencies.
Only commercial radios and scanners built in the past decade or so will do 6.75/2.5KHz channel spacing, so as the FCC and NTIA assign more and more new frequencies you will have issues using older radios on these new frequencies.
So I know you are asking yourself, What the Hell does this have to do with me?
If you are planning on using an old scanner or a ham radio to listen to public safety traffic, not only are you going to have low volume issues, and possibly issues with interstitial frequencies, you will also not be able to monitor the new frequencies.
IE, I tested my FT-60R and when I punch in 154.2725 it rounds down to 154.2700