Distance learning/ITFS/EBS

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  • #9507
    nosignalallnoise
    Participant

    “It was analog video so a separate network had to be constructed using video/audio over twisted pair separate from the schools data network. This was achieved using a baseband switcher like in a TV broadcast station at that time. Here’s what is looked like:”

    Does anybody even use ITFS for that any more, since Sprint basically pwnz it now? What’s the general current state of ITFS in this area these days?

    Several years ago I got to play with a friend’s ICOM handheld and tuned around in that area a bit. I could kind of hear audio off some analogue ITFS service (think it was one of OPB’s services on the Oregon WIN) but there was too much adjacent-channel interference (Clearwire?) to be listenable.

    #9509
    Andy Brown
    Participant

    A bunch of school districts had ITFS in place previous to the growth of fiber optic availability through landline carriers in the late 90’s. Since then, I do not know if they held on to those microwave frequencies.

    P.S. The system at http://mediaeng.com/chief_leschi_system.html had ample inputs to accept additional “B” type sources such as TVRO and ITFS, but the BIA money did not include enough for both so they went with TVRO which was added by another subcontractor.

    Interestingly enough, the VLAN multiplexers were using technology similar to satellite/ITFS using analog composite baseband signals for video (but using FM for video unlike old NTSC broadcasting that had AM video modulation, actually VSB) and FM for audio (audio using subcarriers at 10.7 and 11.5 MHz). Satellite and ITFS used the same plan with audio at 5.8, 6.2, 6.8 and 7.5 because the channels weren’t as wide as the fixed twisted pair VLAN could provide. TV ENG at 2 GHZ was narrower yet and used audio subcarriers at 4.83 and 5.8 MHz.

    The baseband crosspoint switching router in the VLAN had plenty of bandwidth to accomodate a wider signal. Over twisted pair CAT5, you could send the composite over 4000 feet. The campus was four buildings and there were some long runs.

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