If the first generation of digital was PACKET-IRLQ-Echolink-APRS (generation
Zero was CW and RTTY), then the second generation was D-Star. D-Star brought
everything together along with digital voice. While D-Star is great, its
technology is already dated.
So what will the third generation of digital radio look like? I am thinking
that it will be more like the Trunked Radio (digital) or either P25 phase II or
TETRA. TETRA is 25 Khz wide channel with four TDMA slots with a very low cost
handheld (under $400) and is used in Europe within the 400 Mhz band. P25
digital currently is 800 Mhz, FDMA (25 Khz channel). Phase II will move to a
single 12.5 Khz channel with two TDMA slots. Additional capacity can be added
with additional repeaters (12.5 Khz) working under a common controller.
So, could we do something like that within amateur radio? We have to be above
220 Mhz in order to get 9600 baud rates. If we look at bands, 900 Mhz may be
to high and 440 may be too crowded. It was suggested that we go 220 as it
gives a mix of characteristics of both 2m and 440 and is fairly open. If we go
to P25 (phase II) we do have to overcome the cost of the VOCORDER. That could
be done with open P25 in software in an software defined radio (SDR). Most of
the military radios these days are SDR.
A trunked system would allow us at least state wide communications that would
include voice, data and position reporting (APRS). Also that one could link
into the system via VoIP (like D-Star or Echolink). A small community might
only need a single repeater with two FDMA slots. In big cities it might be
that there are multiple repeater sites with two or three repeaters (4 to 6
slots). Also five simplex frequencies for tactical operations or remote areas
(like using 146.52 and 144.39 now).
Using 9600 baud rates would allow for greater amounts of information. And an
SDR would be flexible enough to handle such data rates.
Any comments or ideas? Let the flame wars begin.
