[chirp_users] GMRS Channel Locking

Chris Romp chrisromp+chirp at gmail.com
Wed Feb 23 10:45:00 PST 2022


Agreed - I was trying to figure out if the channel/frequency mapping
is a Part 95E requirement. If it is, I cannot find it. The only place
I can find a reference with channels is under Part 95B, "FRS
Channels," but the equivalent (?) regs for GMRS simply state the
frequencies allowed, which makes sense.  Some links below.

47 CFR Part 95B §95.563 "FRS Channels" -
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-B/section-95.563

47 CFR Part 95E §95.1763 "GMRS Channels" -
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E/section-95.1763

Thanks,
Chris


On Wed, Feb 23, 2022 at 10:37 AM Nigel A. Gunn G8IFF/W8IFF
<nigel at ngunn.net> wrote:
>
> OK Chris.
> In most radios that come pre-programmed by the manufacturer, as opposed to the random channels that a manufacturer seems to leave in there after testing, I believe they are locked by the firmware in order to comply with a country's frequency allocations and get type approval in that country. Don't know if the FCC insists on that.
>
>
> > On 23/02/2022 13:27 Chris Romp <chrisromp+chirp at gmail.com> wrote:
> >
> >
> > Hi Nigel,
> >
> > In the case of the RB26 that doesn't appear to be true: I have one in my hands that's configured for repeater 18 (625) on the radio's channel 1, and they seem perfectly happy to radio clone that configuration to other units. It may be that other radios do enforce it in the firmware (e.g. BTech GMRS V1, though I haven't tested that).
> >
> > Jim KC9HI explained that CHIRP is doing this because that's how the OEM software behaves in the case of the RB26. I've since pulled down their (terrible) software and verified that, and emailed Retevis to ask why (not optimistic I'll get a useful response).
> >
> >
> > Thanks,
> > Chris KN6LEH
> >
> >
> > On Wed, Feb 23, 2022 at 10:16 AM Nigel A. Gunn G8IFF/W8IFF <nigel at ngunn.net> wrote:
> > > Nothing to do with Chirp. The radio's firmware doesn't allow them to be changed.
> > >
> > >
> > >  > On 23/02/2022 12:44 Chris Romp <chrisromp+chirp at gmail.com> wrote:
> > >  >
> > >  >
> > >  > Thanks, Jim, for that info. I've reached out to Retevis to see if
> > >  > they have any input. Would it basically be a requirement for CHIRP to
> > >  > support assigning any GMRS frequency to any channel for Retevis to
> > >  > change their OEM software, even if the radio supports it?
> > >  >
> > >  > Thanks again,
> > >  > Chris
> > >  >
> > >  > > On Mon, Feb 21, 2022 at 6:08 PM Chris Romp <chrisromp+chirp at gmail.com> wrote:
> > >  > > >
> > >  > > > Hello,
> > >  > > >
> > >  > > > I have a question about how CHIRP handles GMRS radios, e.g. BTech GMRS V1 and Retevis RB26. I've noticed that CHIRP enforces that GMRS channels follow the FRS channel number and frequency pairings, e.g. Channel 1 is 462.5625, Channel 18 is 462.625, etc. I've been trying to find in the FCC regs if this mapping is a requirement of GMRS operation. The only place I've found the channels spelled out is on 47 CFR Part 95B ?95.563 "FRS Channels" (link), but GMRS seems only to specify the frequencies and bandwidth which may be used via Part 95E ?95.1763 "GMRS Channels" (link). It's entirely possible that I've missed the clause requiring this mapping, and I am not a lawyer, so apologies if I've overlooked it.
> > >  > > >
> > >  > > > When I am programming a GMRS radio, I don't always want what my family refers to as our "channel 1" to be 462.5625. Likewise I may want to set up different repeaters that may use the same frequencies, but different tones (especially on radios where I cannot edit the tone from the radio itself) I am able to program the RB26 to accept an alternate GMRS-legal frequency with a little trickery, so there does not seem to be a firmware restriction enforcing this and it hasn't bricked my radio (yet).
> > >  > > >
> > >  > > > Would it be possible for CHIRP to accept GMRS-legal frequencies in any channel slot, and not require the FRS channel-frequency mapping?
> > >  > > >
> > >  > > > Thank you,
> > >  > > > Chris Romp
> > >  > >
> > >  > > The BTECH GMRS-V1 channel assignments are in firmware. Even if CHIRP
> > >  > > would let you put in different frequencies, it wouldn't make any
> > >  > > difference. Channel 1 will always be 465.5625 MHz.
> > >  > >
> > >  > > The Retevis models are programmed to match how the OEM software
> > >  > > behaves. Some of the newer Retevis models let you program the GMRS
> > >  > > frequencies in the radio however you please.
> > >  > >
> > >  > > Jim KC9HI
> > >  > _______________________________________________
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> > >  > This message was sent to Nigel Gunn, W8IFF at nigel at ngunn.net
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> > >  > To report this email as off-topic, please email chirp_users-owner at intrepid.danplanet.com
> > >
> > >  Nigel A. Gunn, ///shoulders.outwards.resolutions tel +1-937-971-0366
> > >  Amateur Radio G8IFF W8IFF and GMRS WRBV701, e-mail nigel at ngunn.net www http://www.ngunn.net
> > >
>
> Nigel A. Gunn, ///shoulders.outwards.resolutions tel +1-937-971-0366
> Amateur Radio G8IFF W8IFF and GMRS WRBV701, e-mail nigel at ngunn.net www http://www.ngunn.net


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