On 8/2/2010 11:23 PM, Glenn Little WB4UIV wrote: > I do not know about Nextel, but, the US DTV signal fits into a 6 MHz > bandwidth. > We use a mask filter to ensure that the bandwidth is no more than 6 MHz. > 500 kHz from band edge<= -47 dB > 6 MHz from band edge<= -110 dB > > 73 > Glenn > WB4UIV
And that's why we see noise in the -60 to -90 dBm range 1 to 2 MHz beyond the band edges 10-20 miles from the transmitters... (thank god the ch2 here moved up to 17...6M is usable again!) 500 KHz from the band edge @ 47 dB down on a transmitter that is, say, 10,000W...10KW is +70 dBm minus 47db is +23 dBm, or 200 mW. Free-space loss at..let's be conservative and use 860 MHz (I happen to have the Bird mouse pad in front of me) @ 10 mi is 115 dB. +23 minus 115 is -92 dBm...nah, no one will hear that...free-space loss @ 150 for the same distance is 100 dB, my chart doesn't have 50 Mhz, but I suspect around 90-95. And while Nextel is better than that, because the Nextel channels are interspersed with other (25 KHz spacing), it causes total LOS sometimes as far as a mile or two from a tower. That's why they're moving them up to the top of the 800 band and getting normal 800 users as far away as possible.
