Note also that a 0.005% frequency tolerance is 3 times as big at 450 MHz as it is at 150, hence the wider channel spacing that has been used on UHF in the past.
-Bob N3HAT On Jan 24, 2008 5:16 PM, <[EMAIL PROTECTED]> wrote: > Paul, > the underlying and unexpected contridiction here was not between 15Khz vs. > 20Khz channel spacing but instead between 20Khz and 25Khz channels more > commonly found on UHF which as you know is where GMRS resides. Historically > there's more than enough guard between channels to compensate for slight > overdeviation or slight drift off channel but now everybody wants to tighten > things up so new gear is coming stock with 4Khz max dev associated with > 20Khz channels vs. 5Khz dev which we've all enjoyed for years on 25/30Khz > channels. Seems a bit odd of them to expect no interference problems from > +/-5Khz peak dev on a 20Khz max channel but it is better for us users to > have the option I suppose. > Gary > ---- Paul Plack <[EMAIL PROTECTED]> wrote: > > Gary, 5 kHz deviation with a 3 kHz audio cutoff creates a signal at > least 13 > > kHz wide, counting only the first set of sidebands. That's why many > states > > went from 15 kHz to a 20 kHz channel bandplan on 2m a few years ago. > There's > > nothing inconsistent in the FCC imposing both limits. > > > > 73, > > Paul, AE4KR > > > > _____ > > > > From: [email protected] > > [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > > Sent: Thursday, January 24, 2008 1:33 PM > > To: [email protected] > > Subject: Re: [Repeater-Builder] Re: Gmrs Repeater > > > > > > > > I wrote NARROWER GMRS SPECS. I did not write narrowband. After more > study I > > see some possible contridictions in the rules as currently written for > > example, F3E/G3E GMRS emissions (probably the most common) are limited > to > > 20Khz bandwidth but at the same time those emission types are also > limited > > to +/-5Khz peak dev. I suspect the FCC doesn't really give a damn these > days > > especially with rebanding, auctions, and now a congressional > investigation > > on their doorstep. > > Gary > > > > ---- wd8chl <[EMAIL PROTECTED] <mailto:wd8chl%40gmail.com> com> wrote: > > > [EMAIL PROTECTED] <mailto:n6lrv%40cox.net> wrote: > > > > Good idea Richard especially since Mitreks are wideband radios so > making > > them meet the narrower GMRS specs is probably a monumental task. I > wonder if > > a Mitrek can even meet the required frequency tolerance. > > > > Gary > > > > > > You're not talking about the Part 90 narrowbanding? Part 95 (GMRS) > does > > > not have to narrowband. The 12.5 tertiaries are NB, but the normal > > > channels can stay as they are. > > > > > > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > >
