On 4/7/2010 11:47 AM, k7...@skybeam.com wrote: > Yes, > > > > Tetra 4 slot TDMA over a 25Khz channel, Phase 1 P25 12.5Khz digital over a > single channel, NXDN Kenwood& Icom FDMA 6.25 KHz digital and DMR standard > is TDMA digital over a 12.5khz channel witch is 6.25Khz. I wish Tetra was > here in the USA but were too stupid to think we could follow of what every > other country is using. > > > > Maybe in another 20 years, by that time Europe will have 8 slot TDMA and we > will be using 4 slot, go figure.
Yeah, Tetra is a good format. The 'official' line on why you don't see it in the US (yet) is that propagation delays prevent a user from going beyond a certain distance from a site (which is true), and that that distance is rather short, requiring so many sites it would be impractical out in the sparsely populated parts of the west (with a 7 call you probably know what I mean). Europe doesn't have that problem too much. Yes, there is licensing issues here in the states though. Unlike P25, where about the only licensing a mfg has to contend with is DVSI (which hits everyone on equally hard), Motorola has some of the rights to Tetra, and they have until recently been reluctant to license it in the US. Now there is a group getting Tetra available in the US, and you may see some systems in 5 years or so. It'll be good for an urban area, but you won't see it much outside of big cities. It would be a bad choice for a state-wide system. Except maybe in RI. Course I don't think 700/800/900 is a good choice for a state-wide system anyway...
