[opendtv] Re: FCC Commissioners disagree on media cross-ownership rules
- From: "John Willkie" <johnwillkie@xxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sun, 18 Nov 2007 10:34:32 -0800
Interference from terrestrial sources is more significant at VHF tv
frequencies than are UHF frequencies. As well as the below.
John Willkie
-----Mensaje original-----
De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
nombre de Craig Birkmaier
Enviado el: Sunday, November 18, 2007 5:32 AM
Para: opendtv@xxxxxxxxxxxxx
Asunto: [opendtv] Re: FCC Commissioners disagree on media cross-ownership
rules
At 8:31 PM -0500 11/17/07, Tom Barry wrote:
>Dale Kelly wrote:
>Therefore, it was necessary to temporarily utilize many
>> out of core UHF DTV channels. The FCC, after learning that the VHF band
had
>> very little auction value, also made a number of high band VHF DTV
>> assignments in congested RF areas.
>
>I think this was discussed here before and it seemed that low VHF
>especially (2-5?) was unattractive for for digital TV. Would there
>be some good use for that if it was cleared and auctioned?
From Wikipedia:
VHF frequencies' propagation characteristics are ideal for
short-distance terrestrial communication, with a range generally
somewhat farther than line-of-sight from the transmitter (see formula
below). Unlike high frequencies (HF), the ionosphere does not usually
reflect VHF radio and thus transmissions are restricted to the local
area (and don't interfere with transmissions thousands of kilometres
away). VHF is also less affected by atmospheric noise and
interference from electrical equipment than low frequencies. Whilst
it is more easily blocked by land features than HF and lower
frequencies, it is less bothered by buildings and other less
substantial objects than higher frequencies.
From a California Government report on emergency communications:
http://209.85.165.104/search?q=cache:D_FnPHmhyhoJ:www.assembly.ca.gov/acs/co
mmittee/c22/hearing/2006/may%25202%2520%25202006%2520-%2520joint%2520hearing
%2520agenda.doc+Propagation+characteristics+of+VHF+spectrum&hl=en&ct=clnk&cd
=8&gl=us&client=safari
Overview of Existing Communication Systems
Federal, state, regional and local agency-specific communications are
operating on four different radio frequency bands which consist of
low-band Very High Frequency (VHF), high band VHF, Ultra High
Frequency (UHF), and 700/800 MHz frequencies. Each radio frequency
band presents unique challenges for radio interoperability.
Each frequency operating band has both pro and con propagation
characteristics. One operating frequency band will not suit the needs
of every public safety agency in the state because of geographical
and mission operations differences. The low-band VHF will propagate
the best in rural areas where the foliage is flush and the topography
is mountainous. However, the low-band VHF spectrum is not the best
solution for metropolitan areas and in-building penetration.
Essentially, the low-band VHF signal will not propagate into building.
The high-band VHF spectrum is the best overall spectrum for a
statewide radio system for the type of topography in California.
However, the high-band VHF frequency resources are not available in
California. The UHF is an ideal spectrum for metropolitan areas for
in-building penetration and useable for most of the topographies in
California. However, the frequency resources are not available in
the metropolitan areas of California.
The 800 MHZ spectrum is neither suitable nor cost-effective for the
flush foliage and mountainous areas in California. The 800 MHz
spectrum is very suitable for metropolitan areas and in-building
coverage. However, the frequency resources are not available and the
Federal Communications Commission (FCC) has mandated that no
frequencies be allocated and/or licensed until the rebanding efforts
in this spectrum are completed.
The FCC has reallocated 24 MHz of the 700 MHz spectrum (television
channels 60-69) from the commercial broadcast industry to public
safety. However, the public safety agencies cannot use this spectrum
until the commercial broadcast stations have migrated to their newly
assigned digital modulation broadcast channels. The FCC has extended
the mandatory compliance date for the commercial broadcast industry
to 2009. The new allocated 700 MHz spectrum has the same propagation
characteristics as the 800 MHz band and is not suitable as a
statewide radio communication system.
So it seems that the low band VHF may primarily be useful for FM
broadcasting and emergency services.
Regards
Craig
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