I work in the same place as the gang who put the whole system together. The main MMDS transmitter is on Mt. Wilson. The 100+ digital video channels are encoded as baseband MPEG2 signals at the digital video headend in El Monte, and multiplexed onto a Pac Bell OC-48 ring via a dual route fiber cable up to Mt Wilson (elev 5800'). At Mt Wilson, the signals are modulated onto the MMDS 2 GHz frequencies and beamed out using horizontally polarized microwaves. This signal is transmitted over the entire LA basin, and is strong enough to receive on Catalina Island (26 miles across the sea...), where some additional MPEG2 channels are used for Instructional Television Fixed Services by the school district.
The variable terrain in central and southern Orange County makes it tough to get a line of sight to Mt Wilson, especially south of Santa Ana. Mt. Modjeska (elev 5500') in the Santa Ana Mtns is line of sight to Mt. Wilson, and also beams straight down on a big chunk of Orange County. The horizontally polarized microwave signals from Mt Wilson are received at Modjeska and retranmitted as vertically polarized signals. So, Modjeska is not the main transmitter, but serves as a handy dandy relay site nonetheless.
The horizontal and vertical polarized microwaves enable the two transmitters to have overlap in signal coverage, e.g., in northern Orange County. However, when a vertical polarized receiver is installed and pointed towards Mt Wilson, it will reject the horizontal polarized signal from Modjeska, and vice versa.
This is not a marketing plug, but if I lived in range of the digital MMDS, I would think about it before buying a mini dish that doesn't get local channels. I would also be happy to phone in a disconnect for my crummy picture quality from TCI cable.
|
