31-10-2017, 03:29 AM
Although one might imagine an alternative history in which the channel allocations for a two-programme national service was done with each having an equal allocation of Band I channels, the net result would have been that each might have had two, perhaps three main transmitters in that Band, with the rest being in Band III. Whether that would have been any better is a debatable point.
In the US case, there were five low-band channels, but channels 4 and 5 were not contiguous, thus both could be used in a given area, increasing overall band utilization.
The New Zealand example to which you refer is I think the Te Aroha transmitter in the North Island, which radiated TV1 on channel NZ1 and TV2 on channel NZ3. It was the only one of the seven main transmitters that had both TV1 and TV2 in Band I. The others all had TV1 in Band I and TV2 in Band III. The Te Aroha transmitter is atop the highest peak in the Kaimai range (around 950 metres). From that position it is able to “illuminate” the greater part of the Waikato, including Hamilton city, and the eastern Bay of Plenty, including Tauranga city (of which Mt. Maunganui is a part). As such it had what was probably the largest footprint of any of the NZ VHF analogue TV transmitters. Much of its service area was likely bounded by simply natural running out of signal rather than by topographical obstructions, as often applied elsewhere. Thus, it made sense to assign it a Band I channel for TV2, in order to equalize coverage at the edges. It was vertically polarized. In part that was because the major cities appeared to have first claim to horizontal polarization. But it was logical in that in much of its catchment area, reception conditions were quite clean such that the very poor horizontal directivity associated with the customary 2- and 3-element vertical aerials was not a major drawback. On the other hand, the topographies of say Auckland, Wellington and Dunedin made the better directionality obtained with horizontal aerial arrays highly desirable.
Cheers,
Steve
In the US case, there were five low-band channels, but channels 4 and 5 were not contiguous, thus both could be used in a given area, increasing overall band utilization.
The New Zealand example to which you refer is I think the Te Aroha transmitter in the North Island, which radiated TV1 on channel NZ1 and TV2 on channel NZ3. It was the only one of the seven main transmitters that had both TV1 and TV2 in Band I. The others all had TV1 in Band I and TV2 in Band III. The Te Aroha transmitter is atop the highest peak in the Kaimai range (around 950 metres). From that position it is able to “illuminate” the greater part of the Waikato, including Hamilton city, and the eastern Bay of Plenty, including Tauranga city (of which Mt. Maunganui is a part). As such it had what was probably the largest footprint of any of the NZ VHF analogue TV transmitters. Much of its service area was likely bounded by simply natural running out of signal rather than by topographical obstructions, as often applied elsewhere. Thus, it made sense to assign it a Band I channel for TV2, in order to equalize coverage at the edges. It was vertically polarized. In part that was because the major cities appeared to have first claim to horizontal polarization. But it was logical in that in much of its catchment area, reception conditions were quite clean such that the very poor horizontal directivity associated with the customary 2- and 3-element vertical aerials was not a major drawback. On the other hand, the topographies of say Auckland, Wellington and Dunedin made the better directionality obtained with horizontal aerial arrays highly desirable.
Cheers,
Steve
