Il giorno sab, 14/02/2009 alle 15.36 -0500, Evans Mitchell KD4EFM / AFA4TH FL / WQFK-894 ha scritto: > Look at it this way.... > > this is a straw, this straw carries DV and Low Speed Data > 2.5KHz narrow band > > | | > | 2.5Khz | > | DV | > | | > > This the straw that carries 128Kbps Digital Data > 130KHz WIDE BAND > > | 128Khz | > | DATA | > | | > | | > |-----------------------------| > > This is poor designing, but, if you have studied > the waveform for 802.11 b/g, you will know that > in 802.11 g uses more bandwidth space then b (OFDM vs CCK) > > You need more power for more bandwidth, therefore > you need more signal on 23cm for the same reasons, > larger bandwidth needs more signal input / output. > Problem is, no one makes an bi-directional amplifier > that can switch fast enough for D-Star Data. SO with > that, you have to factor every "SPECK" of gain you > can get, and have absolute Line Of Sight. > > Right now, our system can do 35 air miles Near-LOS > with our PORT A DD at 360' and the far end user at 50'. > He can establish communications with the DD box. > > WE DO KNOW that beyond 40 miles, it does fail with > only a 9Dbi gain at 60 feet, BUT they can decode the DD. > They also have a 24Dbi parabolic at 40 feet and hit > the DD rock solid from 40 miles out. > > So again, GAIN IS EVERYTHING. Just because you can get in > on voice, does not mean you have to POW to make it on DD. > > Evans >
Evans, thank you a lot for your contribution, surely our LOS isn't very clear because than the module is located to 1748 feet we cannot reach 15Km. I go to esxperiment more and write more about the experience. 73 de Antonio IW2OAZ http://www.iq2gm.com
