On May 29, 2007, at 11:42 PM, [EMAIL PROTECTED] wrote: > At 5/28/2007 12:27, you wrote: > >> Also, as you pointed out, D-Star digital voice is a narrowband signal >> occupying only about 6Khz vs. the 25Khz or so that amateur >> repeaters have >> often required to date. It is difficult to do a comparison between a > > While the typical 50 dB analog NBFM (5 kHz deviation) bandwidth is > ~20 kHz, > the 50 dB bandwidth of DStar appears to be about 10 kHz. Here in > SoCal > we're proposing 10 kHz channel spacing for DStar, digital P25 & any > other > "very narrow band digital voice", or VNBDV, systems.
Discussion here locally is leaning toward 12.5 KHz spacing for what's really needed for P25 Phase I systems, not 10 KHz. The discussion was also backed up with tests of real-world BER (bit-error rate) at closer and closer spacings (overlapping) by a local Amateur with access to the appropriate P25 test equipment. In lab testing, 10 KHz spacing and it's effect on P25 BER is not real pretty. (Good luck finding test equipment that supports D-Star. Ever.) Another challenge on the P25 front is that many people will probably desire initially to deploy it using Quantars or other similar repeaters that can operate in mixed conventional analog, and conventional digital modes -- "mixed mode" operation. -- Nate Duehr, WY0X
