Monday, November 17, 2008

Legality of amateur ATSC

Just to dot the eyes and cross the Ts....

97.305(c) lists on a per-band basis the parts of 97.307(f) that apply. 97.307(f)(8) applies to all amateur allocations above 51 MHz (except for the 219-220 MHz 1.25m sub-band). 97.307(f)(8) says,

(8) A RTTY or data emission having designators with A, B, C, D, E, F, G, H, J or R as the first symbol; 1, 2, 7 or 9 as the second symbol; and D or W as the third symbol is also authorized.

The emission designator for ATSC DTV is C7W. That is, it is a vestigial sideband modulation (C), two or more digital channels (7), and a combination of different information (W). That means that, according to 97.307(f)(8) ATSC is allowed. Of course the lowest band where even a single ATSC channel would actually fit is the 70 cm band, so it is unusable on 6m, 2m and 1.25m.

The full designator for ATSC is 5M38C7WWT - the 5M38 indicates that the bandwidth is 5.38 MHz (though the channel is 6 MHz wide, there are 300 kHz of guard band at each end of the channel). The last W indicates a combination of video and audio and the last T indicates that the multiplex is via time-division.

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