Quote:>There aren't any VHF digital TV signals.
Not today. But there will be, when the Big Switchover occurs. A
significant number of stations which currently have their NTSC analog
signals in the VHF range, and which have a temporary UHF allocation
for their ATSC digital signals, will be moving the digital signals
down to their VHF frequencies when the NTSC shutoff data occurs,
rather than giving up the VHF frequency entirely.
There are a couple of reasons why this is being done. I believe that
it adds up to "better digital coverage" - better antenna site, better
transmitter, or (most commonly I think) a larger distance to the
nearest competing station on that frequency. Some stations
(especially in crowded urban areas) were stuck with UHF transition
frequencies that have significant competition in nearby cities, and
aren't allowed to transmit at full power... the band's pretty full.
Most of these stations have VHF allocations in the highband (channels
7 through 13). There are a very few stations in the VHF lowband
(channels 2 through 6) which will be running ATSC digital in the
lowband. but I'm told that this is being discouraged by the FCC and is
technically less than ideal (more impulse-noise interference in the
Quote:> If one lives any distance from
>a station transmitting in HD or SD, it is necessary to have an antenna
>with plenty of UHF gain. Eleven UHF elements, RG-6 feedline and an
>indoor, variable gain preamp give me twenty or so digital channels from
>my local area and from the Pittsburgh area. This works for my living
>room Hi-Def set or for the HD PCI card in the computer near the hamshack.
In many areas of the country, a UHF-only antenna will prove adequate
for ATSC reception.
In those areas in which one or more stations will be transmitting ATSC
in the VHF band after The Day, an antenna with decent gain and
directionality at both UHF and VHF will be necessary if you want to
get all of the available channels. In most cases, UHF plus VHF
highband will be adequate. A very few cities will require antennas
that handle the VHF low-band as well. People jn these areas who have
bought UHF-only "digital TV" antennas may be in for a rude shock.
The same designs that have been sold for decades (i.e. log-periodics
with additional reflectors and elements for UHF) should work just
fine. A rotator may be useful or necessary.
The FCC's rulemaking document (latest version I know of) has a table
of the actual frequency allocations for DTV, including coverage areas
and interference levels:
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