In article c,
Roland Latour wrote:

On Wed, 07 Jan 2009 22:48:57 -0800, David Nebenzahl wrote:


So what are they going to use those old VHF
channels for, do you know?

It's my understanding they will be used for wireless networking.

There's been talk about that, but the main "target" was supposed to be
"public safety" - AKA fire, cops, ambulance, etc.

The wireless networking concept is/was aimed at so-called "white spaces"
between current TV channels - sort of "slipping it into the gaps"

One
problem with 802.11 at 2.4GHz (which I currently use over longish
distances [2-7 miles] here in rural Oregon) is that the signal won't go
thru trees. VHF doesn't have that problem. VHF will also go thru most
building walls.

VHF has its own set of problems for use in wireless networking. Yes,
it'll give better "penetration", and all other things being equal,
longer distances. But when you drop in frequency, you also drop in
information-carrying capability - Current wireless, running in the 2.4
GHz range, has *LOTS* of "cargo space" available, so top speeds possible
with it are much higher than what can be had from a signal in the VHF
bands (which are *WAY* down the scale: 54-88MHz for "VHF-Lo" - channels
2-6, and 175-216MHz for "VHF-Hi" - channels 7-13) Lower frequency =
lower information carrying capability. The most clearly visible
illustration of this would be comparing the AM and FM broadcast radio
bands - look at how cheesy an AM station sounds compared to an FM
station. PART of the difference is the modulation scheme, (Amplitude
Modulation versus Frequency Modulation) but a much larger part of the
difference comes from the amount of information each band can carry - AM
broadcasting is done on frequencies between about 500 and 1600
*KILO*Hertz, while FM broadcasts are done on 80-ish to 108-ish
*MEGA*Hertz. Higher frequency permits more information per unit of time
to be moved. But it trades off distance the information can travel
intact - Some of the so-called "clear channel" AM stations can literally
cover the country from coast to coast with good strong intelligible
signal, using only 50 *KILO*watts. An FM station running a full
*MEGA*watt is hard-pressed to get a useful signal out past about 100-150
miles.

Shifting wireless down to the VHF bands will give slower, but
further-reaching, wireless connections. For some folks, "some but slow"
is one helluva lot better than "fast but nothing", but in general, most
of the general public is stuck in a "gotta be faster Faster
FASTER!!!!!!! to be any good" mindset, so I'm wondering if that idea is
*REALLY* going to get any traction...

--
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