Charles W. Rhodes
With the end of the FCC’s spectrum auction in January, it’s time to measure its damaging effects on broadcasters.
In the past, I have written about out-of-band (OOB) interference between ATSC signals in different bands: the low VHF band into a high VHF channel and a high VHF band ATSC into a UHF channel.
It’s a given that there is going to be considerable “channel shuffling” after the upcoming television broadcast spectrum auctions.
In its recent Report and Order, the FCC revealed 11 scenarios under consideration for a 600 MHz Band Plan following the spectrum auctions.
By now almost everyone knows the NAB has filed a lawsuit against the FCC over its spectrum auctions TV channel repack.
All third-order intermodulation products, (IM3 and Triple Beats), occupy three contiguous channels, so there can be interference to reception on Chs. 30, 31, 32, 33, 34, and 35.
The most amazing finding from the FCC tests of converter boxes is the number of such toxic channel pairs there are.
His trouble started suddenly one evening when he discovered interference across the high VHF band that he had never had before.
This column has used the term “D/U ratio” (desired/ undesired) in describing how the FCC might repack the UHF TV spectrum.
Last month, this column introduced a scheme for allocating UHF band channels by analyzing a set of contiguous channels for a given community.
Last month we discussed the restrictions that the FCC must work under in repacking UHF broadcast spectrum.
Without any changes to OET-69, the commission could not take up any additional planning criteria such as interference between DTV signals having a channel relationship other that N±1 and N.
Our tests showed that the double-conversion tuners tested were more vulnerable to interference than the converter boxes with a single-conversion tuner.
The FCC regulates co-channel and adjacent channel interference by its channel allotment plan. It does not regulate “taboo channel interference,” a term left over from analog television.
With repacking now in the future for many UHF broadcasters, the problems of interference between DTV signals crammed into Channels 14–29 for example, need to be reconsidered.
If my antenna is on my rooftop, everything is probably OK, but if my antenna is indoors, it may pick up enough signal power from a nearby cellphone to block DTV reception.
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