Digital OTA TV adjacent interference

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  • #26836
    mwdxer1
    Participant

    Out here on the Northern Oregon Coast we have several TV translators.
    2(26)
    6 (34)
    8 (17)
    10 (23)
    12 (21)

    There is a CP to move 51 (KHPN) to 22 and change location to Megler MT where the other translators are. 21 (12) runs 1.86 KW ERP and 23 (10) runs 5.7 KW ERP. the CP for 22 is for 15 KW ERP. Will there be any interference between 21-22-23? I am not sure if Portland has any adjacents, but Seattle does. With analog there would be no way the FCC would okay an adjacent, but I would guess digital offers less interference. I presume both 12 and 10 have been contacted. Any thoughts? Thanks.

    #26840
    jr_tech
    Participant

    OTA, we have close spaced string of
    49,48,47,46,45,43,42,40 in Portland. Is there interference? Likely, but from my location it is difficult to judge. Interesting atricle here:

    http://www.tvtechnology.com/digital-tv/0148/the-fccs-dtv-interference-dilemma/273234

    #26844
    Alfredo_T
    Participant

    In reading the above tvtechnology article, I noted that tuner-on-a-chip receivers with untuned front ends have become the norm in contemporary DTV designs. A variety of chip makers have been pushing these ICs since the early 2000s. From a performance standpoint, this is not a good way to build a receiver, but from a the standpoint of cost of manufacture, it’s great. Remember the trinity of good, fast, and cheap.

    #26850
    Andy Brown
    Participant

    OTA has little sway in tech decisions anymore since most TV receivers these days hook up to another box being fed by satellite or cable or the net. Also, fast and cheap will always be the selection of consumer electronics manufacturers over quality. The development of better cheaper SMALLER Q filters will continue but until then, don’t expect any changes.

    Here are a few thoughts:

    1. If there is a fundamental, there will be harmonics. Normally, 2nd harmonics are weak in comparison to the 3rd and other odd harmonics, but in high power the second harmonic is a consideration. Having said that, it is a fools errand to try and use theory to steer the ship (see jr tech’s link). Broadcasting in the U.S. has mostly relied on the ‘wait ’till it squeaks’ method before applying any lubricant. Since repacking and continuous channel DTV signals are just in the infancy stage, there are less real world situational feedback sources to let the FCC know ‘Hey, this ain’t working.’

    2. If there are harmonics, there will be IMD and THD. It’s a fact of physics. You don’t even need a second signal because the harmonics of the fundamental create these interacting with itself.

    3. If there are multiple signals, you can add ACI to the list.

    4. Cable and satellite use different methods then OTA, so there are different problems with interference.

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