Technically we are both right, NXDN uses AMBE over 4FSK and D-STAR uses AMBE over GMSK (in current radios) but can also be run over 4FSK according to the specification.
--- In [email protected], "Trevor ." <m5...@...> wrote: > > The Icom and Kenwood commercial systems use a different modulation system > hence the narrower bandwidth. > > The current modulation scheme for D-STAR is really designed for 10 kHz > channel spacing, although it can just about be squeezed into 8.33 kHz > channels. You cannot acheive 6.25 kHz channel spacing D-Star is a real world > environment. > > The Icom/Kenwood PMR system uses the same Codec as D-Star with 3200 bps Voice > and 1200 bps data but they don't use GMSK. > > Addition info is on ICOM-UK's website at > http://www.icomuk.co.uk/categoryRender.asp?categoryID=3776 > > Perhaps the challenge for Amateurs is to developed a modulation scheme that > can handle 3200/1200 Voice/Data and fit into 5 kHz or less channel spacing. > > 73 Trevor M5AKA > ---- > NXDN - Association of American Railroads (AAR) > http://falconinfo.blogspot.com/2008/09/aar-chooses-nxdn-digital-standard.html > > --- On Fri, 2/10/09, John Hays <j...@...> wrote: > > From: John Hays <j...@...> > Subject: Re: [DSTAR_DIGITAL] Re: ARRL Approves Study Committee to Research & > Develop Plan for Narrowband Chan > To: [email protected] > Date: Friday, 2 October, 2009, 11:14 PM > > > > > > > > > > > > > > > > > > > > > > > NXDN uses the same codec/modulation as D-STAR, that is why D-STAR DV is > claimed to be 6.25 Khz., the radios may just not be as tight. I think the > Utah VHF Society studies showed that different models of Icom D-STAR radios > exhibited different RF characteristics. http://utahvhfs.org/dstar.html -- in > figure 4 at http://utahvhfs.org/dstar_channel_spacing.html it says that two > D-STAR signals of equal strength can co-exist at 6.25 Khz. spacing. > > On Oct 2, 2009, at 2:49 PM, Trevor . wrote: > But commercial systems (NXDN) with mobiles, handhelds and repeaters that use > 6.25 kHz channel spacing have been available for years - both Icom and > Kenwood are active promoters of the system which uses a far more efficeint > modulation techique that D-Star, see > > 2005 - Icom and Kenwood demo 'Very Narrowband Digital Communications > Technology' > http://www.southgat earc.org/ news/apr2005/ icom_kenwood_ demo.htm > > 2008 - The Gadget Show tests digital and analog walkie talkies > http://www.southgat earc.org/ news/november200 8/gadget_ show_radio_ > tests.htm > > 73 Trevor M5AKA > .. > > John D. Hays > Amateur Radio Station K7VE > PO Box 1223 > Edmonds, WA 98020-1223 VOIP/SIP: j...@... > Email: j...@... >
