The GMRS primaries are spaced 25 kHz apart from each other, not 20 kHz. The interstitials are also spaced 25 kHz apart from each other but are offset by 12.5 kHz so they are spaced in between the GMRS primaries.
Regarding selecting the spacing to select the channel bandwidth: An older "wide" bandwidth channel is often referred to as a 20kHz or 25kHz channel and a "narrow" bandwidth channel is often referred to as a "12.5kHz" channel. Note that the "25kHz" (or 20kHz) and "12.5kHz" choices are usually what you select in the programming to select channel bandwidth. HOWEVER, the 25kHz (or 20kHz) and 12.5kHz desginations are NOT the bandwidth of each. The actual occupied bandwidth is narrower for each channel. The 25kHz (or 20kHz) and 12.5kHz designations in the programming simply refer to the normal channel spacing in the band for a wide or narrow bandwidth channel, respectively. It's a bit of a misnomer in the industry but something to be aware of. Clear as mud, eh?
My first GMRS license in 1992 allowed 20kHz of OCCUPIED bandwidth. The emission designator on the license was 20K0F3E. It worked fine for 25kHz spaced channels. All of my newer equipment won't do 20kHz of occupied bandwidth. The most they will do is 16kHz (16K0F3E) of occupied bandwidth when programmed to "25kHz" mode.
GMRS can use "wide" or "narrow" bandwidth. The FRS/GMRS bubble packs are already using narrow bandwidth ("12.5kHz") on all 22 channels even though they are only required by FCC rules to be narrow on the FRS channels. Older GMRS systems used "wide" bandwidth on all GMRS primaries AND the 7 GMRS interstitials, now shared with FRS 1-7. GMRS operation on FRS 8-14 is NOT allowed at all due to GMRS's higher power operation, wider bandwidth than FRS, and being spaced only 12.5kHz away from the GMRS repeater inputs. FRS 8-14 are part of the GMRS allocation but aren't used by GMRS to protect the repeater inputs. GMRS operation on FRS 8-14 is NOT allowed at all at any power level.
Even though I'm using type accepted commercial gear (i.e., specifically has Part 95 in addition to Part 90) on GMRS, I'm using narrow bandwidth on all GMRS primaries and the GMRS interstitials. I did it to be compatible with the bubble packs and to solve adjacent channel splatter problems from bubble packs in my neighborhood operating on FRS channels adjacent to whatever GMRS primary channel I'm on. I found all of my adjacent channel splatter problems went away as soon as I made the switch from wide to narrow bandwidth opertion. I've found my radios also perform a little better in narrow mode. I'm also going with the flow of everything else in the land mobile industry as older wide bandwidth equipment is being phased out.
Regarding channel numbers, there is no official channel numbering in GMRS. For example, 462.625 is channel 18 in the Moto TalkAbout bubble packs while 462.625 is channel 9 in some older bubble packs. Most seem to be following Moto's example in the bubble packs where 1-14 are the 14 FRS freqs (1-7 shared w/GMRS) and 15-22 being the GMRS primaries.
Recommendations:
- On the 7 GMRS interstitials, shared w/FRS 1-7, use "narrow" ("12.5kHz") bandwidth mode.
- On the GMRS primaries, use "wide" ("25kHz") or "narow" ("12.5kHz") mode. Your choice. I recommend using narrow mode because I've found it helps eliminate adjacent channel splatter problems in the band.
- If you're programming a GMRS repeater pair to use on an existing repeater somewhere, program either wide or narrow mode, depending on what the repeater is set up for.
Good luck.
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-RE
Okay so i Stumbled across this Post looking for answers to my question about FRS/GMRS
Khz Spacing.
Not a expert but a individual who came a ways learning the ropes from others...
I need a real facts!
I have a Motorola CP200 UHF and im trying to program the radio to FRS/GMRS.
This can be a bit Confusing! I know a True GMRS radio is wideband at 25Khz.
The Radios they sell at Wallmart, Bubble pack radios like Uniden, Motorola, Cobra ect....
What is the Khz for FRS 1-14 and
What is the Khz for GMRS 15-22
I know GMRS is 25Khz, But what about Bubble Pack GMRS/FRS?
Every day there is people all over using Uniden radios Bubble packs and im trying to talk to them on
Simplex and i can never get a reply back.
Also can you explain the difference in 20Khz and 25Khz?
Do all FRS/GMRS Radios Use Narrowband on GMRS?
Any Facts would be appreciated!
Im expecting to use My 5 watt CP200 as FRS/GMRS for Survivalist.
I tried using CSQ on Transmit and Receive and no luck.
I tried using TPL 67Hz on Transmit and Receive still no luck.... Isnt PL67Hz same as CSQ?
What Khz and TPL do i need to Talk to Bubble pack radios?
