[opendtv] Re: FCC Commissioners disagree on media cross-ownership rules
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sun, 18 Nov 2007 11:01:13 -0800
Craig posted:
> 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)
Wikipedia's comparison is relative to HF frequency propagation and in that
context, is correct. However, as a practical matter, low band VHF (ch 2 thru
6) has significant propagation issues including atmospheric ducting,
aircraft interference (flutter) and the susceptibility to industrial and
other impulse noise. LB VHF is marginally acceptable for analog TV service*
but, given the more stringent criteria to achieve reliable DTV reception, it
is generally unacceptable for that service.
Anyone with experience in LB VHF broadcasting knows of and has likely
experienced serious reception degradation and disruptions from such
phenomena. However, this degradations severity is dependent upon geographic
location and there are a few stations that chose to remain on the LB
channels for DTV service. I assume they are located in those more benign
areas.
* Channels 2 thru 4 are more prone to such problems than channels 5 and 6,
though six has upper adjacent channel issues with FM radio.
> -----Original Message-----
> From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Craig Birkmaier
> Sent: Sunday, November 18, 2007 5:32 AM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [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 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/committee/c22/hearing/2006/may%25202%2520%25202006%2520-%2
> 520joint%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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