On 5/19/2010 3:29 PM, Steve Bosshard (NU5D) wrote: > The FCC defines bandwidth differently for Amateur vs Commercial - > Amateur bandwidth is -26 db points either side of center in the US. > Seems like LMR / PMR is -60 some odd either side of center. When I > looked at the mask it seems like reality for DSTAR was around 12 1/2 > khz occupied bandwidth @ - 60 points - about the same as narrowband > (12 1/2 khz) LMR.
Gold star! You got it! (They're virtually the same.) For the computer/data geeks in the crowd, one can do the math from the CODECs and figure this out real easy too... voice still takes a specific amount of bandwidth -- albeit compressed heavily by a single manufacturer's chipset, because no one else competes in that market -- and that'll always equate to the same on-air RF bandwidth... CODECs are King. Modulation is just how you get that bitstream from "here" to "there" nowadays. If you see any product that doesn't announce the use of a new CODEC to compress down good old Nyquist's theoretical minimum bandwidth for A-to-D sampling rates to something smaller/compressed... you don't even need to read the rest of the Marketing "slick". It's the same as everyone else. Similar thing happens in "my" industry. Everyone claims to have a better way to skin the videoconferencing cat, but we're all using the same DSP chipsets, and they can do exactly the same things... Or, at the end of the day, only those who invest in mathematicians to write new algorythms and CODECs, gets to really say they've changed anything... then you release them to the standards committees... they get reverse-engineered, and the game begins again... Nate WY0X
