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Discussion Starter · #1 ·
Well I had hoped to avoid displaying my ignorance in public, but after browsing around for a couple of days I haven't found the answer, so here goes...


In my area, 6 of the 7 stations I can pick up OTA are broadcasting in UHF. One (of course it's ABC home to LOF and Alias - two of my favorite shows) is in VHF. As much as I'd like to see them in HD, I can't bring myself to spend a weekend installing a big ol' combo antenna and pulling cable, fishing it through walls, etc. I'm going to stick w/my Silver Sensor. My question is, why do some stations broadcast in VHF and some UHF? Granted, I'm from the age of cable (the first antenna I've ever used is my trusty SS) so I don't think I ever bothered to learn about the pros and cons of UHF vs VHF.


Someone wanna help me out? ;)


Brian
 

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Many stations will elect to broadcast using VHF when that frequency is available to them. They can achieve an increased coverage area using less power at VHF because of the larger antennas that are used to recieve VHF and to a lesser extent the fact that VHF can propagate over the horizon better.


Most stations don't have the option and need to use a UHF channel because of the lack of a VHF frequency alloation from the FCC.
 

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What VHF channel do you need? Many UHF antennas like the Channel Master 4228 can provide adaquate reception down to and including channel 7.
 

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Also, I believe I read that after the changeover is complete, many stations will revert to their original VHF frequencies for their digital broadcasts, meaning that even in areas where all the channels are UHF today, the situation will likely change in a few years.


Xesdeeni
 

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Discussion Starter · #5 ·
Quote:
Originally posted by NightHawk
What VHF channel do you need? Many UHF antennas like the Channel Master 4228 can provide adaquate reception down to and including channel 7.
Well, that's the thing. I'm, perhaps, a tad lazy - and am willing to forgoe ABC because a wee Silver Sensor that requires no weekend long wiring pulls will tune in *all* my UHF stations. I just wondered why only 1 of 8 broadcast their digital signal over VHF.


Brian
 

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Like Night Hawk mentioned, VHF allows a station to broadcast at lower power. Lower power means cheaper electricity bills. Follow the money!


Plus stations think that a lower frequency number is "important" to people. (Kinda like New York City's 212 area code is more desirable, because it was easier to dial on rotary phones, and who uses those anymore!?!)


Why there is only one VHF in your area is likely because there were no more available UHF frequencies. (At least in Chicago, CBS-DT was given VHF 3, and there are no more available UHF frequencies)
 

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Just to confuse the matter. My analog locals are on channels 12, 34, 40, and 46. Their digital versions are 4, 7, 8 and 42. I have a small VHF/UHF outdoor antenna which works well for all but 42. Forget the analog channels.
 

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Discussion Starter · #9 ·
Quote:
Originally posted by brenden
Why there is only one VHF in your area is likely because there were no more available UHF frequencies. (At least in Chicago, CBS-DT was given VHF 3, and there are no more available UHF frequencies)
Sigh.


Seems like it woulda made more sense to stick UPN, WB on VHF, heck they should move Telemundo or Univision over to get all the major networks on *one* antenna - but of course that would make too much sense eh? ;)


Brian
 

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Brian, if you are reasonably close to that VHF HD transmitter, you should be able to recieve their signal with just a pair of rabbit ears. Combine it with the signal from you SS and you should be done. With a little luck, there should be no need to crawl up on the roof with a big combo antenna.
 

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Brian,


Before I put up my UHF/VHF antenna I had a 30 year old UHF only one, sorta like one of the Radio Shack double bow tie, but had 4 "bows" arranged in front of a bbq grille-looking grid. I'm sure you're familiar with that type of antenna. Anyway I got Channel 30's digital HD pretty decently with it even with my crappy E-86 receiver. Their digital signal is on channel 9, and the bow-tie type UHF antennas do a decent job.


I know where you're coming from about getting on the roof and such--I have very severe acrophobia, myself--get cold sweats on a 6 foot ladder. It was a real ordeal to get up on my very gently pitched roof and put up my new antenna, which didn't help my E-86 much if any but sure works great for my HD-200. I just wanted reliable HD so badly that I sucked it up and did it. I swapped out the antenna and cable runs and now get very good reception of all 9 or so of the local digitals here in Fresburg, where with the old antenna only ABC of all the HD channels was even halfway reliable. Oddly, even though the old antenna was UHF it got digital channel 9 better than any of the others that were in the UHF band.
 

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I'd wondered in the past why there was such a difference between VHF high, VHF low and the antenna requirements. In looking at the channels and their frequencies, it makes sense. While the channels themselves follow a nice linear progression, the frequencies have huge gaps in them.


Channels 2-6 are considered VHF low and encompass frequency ranges between 55.25MHz and 83.25MHz. Then, there is a huge jump to channel 7 which is on 175.25MHz. I know that FM radio is between 6 and 7 along with a bunch of public service uses.


Channels 7-13 are VHF high and use 175.25MHz to 211.25MHz. UHF begins at channel 14, but the assigned frequency starts at 471.25MHz. It then increases in 6MHz increments all through the UHF band.


Maybe only interesting to a geek like me, but here's a link that shows each channel and its corresponding frequency: http://www.arrl.org/tis/info/catv-ch.html
 

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Quote:
Originally posted by Xesdeeni
Also, I believe I read that after the changeover is complete, many stations will revert to their original VHF frequencies for their digital broadcasts, meaning that even in areas where all the channels are UHF today, the situation will likely change in a few years.


Xesdeeni
Actually, it is the other way around. When the transition is complete, all OTA DTV will be operating in the UHF band. Stations now operating on VHF will have to move to UHF. The VHF spectrum will be auctioned off to the telecommunications industries and will no longer be used for television broadcast.
 

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Has something changed since this statement :


"Under the FCC spectrum plan, we have provided most existing broadcasters with access to a 6 MHz channel for digital broadcasting within a core digital TV spectrum, i.e., TV channels 2 to 51. Because of the limited availability of spectrum and the need to accommodate all existing facilities with minimal interference among stations, however, during the transition some broadcasters would be provided DTV channels outside of this core spectrum (channels 52 to 69). These broadcasters would have to move their DTV operations to a channel in the core spectrum when one became available. Broadcasters whose existing NTSC channels were in the core spectrum could move their DTV operations to their NTSC channel at some time in the future. Broadcasters whose DTV transition channel and existing NTSC channel were both outside of the core area could obtain a new DTV channel when channels in the core spectrum are recovered.


"After the transition period (2006), the VHF channels (2-13) will remain available for DTV and the analog TV service will end on all channels."


"last reviewed/updated 12/22/03"


Xesdeeni
 

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Channels 2-51 are the "core spectrum" to be used for OTA DTV after analog shut off - Unless something changes, that is. Ch. 52-69 are to be auctioned for other uses --- Some of the auctions, I believe, have already taken place.


It's true that FCC Originally planned to use UHF only for DTV, but as the info from FCC in Xesdeeni's post also shows, Channel 2-13 were later added ... 7-13 were added first, 2-6 a little later(all that happened prior to 1998 or so ) ...


Update/edit: For those interested, Channel 2-6 was "added" in the MO&O on reconsideration of the 6th report and order, adopted 2/98. The reasoning behind this is stated in section IIIB, paragraphs 34-46.(out of core allotments are disucssed immediately afferwards). This document is available in various fourms here:

http://www.fcc.gov/Bureaus/Engineeri.../fcc98024.html


Here's an excerpt from this document, Paragraph 41 which contains a summary of the info concerning the decision to add ch 2-6 to the previously decided upon ch 7-51 :


41. Decision. We recognize that postponing a decision on the low-VHF channels has raised uncertainties for licensees whose existing and/or DTV channels are in that portion of the spectrum. We further understand that these uncertainties can make planning for DTV service more difficult and burdensome. We also concur that there is no engineering evidence available at this time to indicate that these channels are unsuitable for DTV operation and such channels offer desirable propagation characteristics for television service. We therefore recognize the benefits of including these channels in the core spectrum. We also note, however, that a DTV core spectrum of channels 2-46 would require significantly more second moves by broadcasters than a core of channels 7-51. In reconsidering this matter, we now believe that the most desirable course of

action is to expand the core to include all channels 2-51.
 

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The VHF channels will remain in use for TV.


There are problems with the low VHF ones 2-6 caused mainly

by two causes:


1) impulse noise


2) the huge size necessary for reasonable antenna gain and directionality


Except for directionality need, the problems these cause can be fixed by simply having the VHF transmitters use a reasonable power. Many

low VHF TV stations are now running only a couple of kilowatts.

This is simply too low: it prsumes a truly gigantic antenna. It is

not clear what is enough ... 20 kW ERPmight be enough, which would be

easily attainable by simply using a legacy 100kW ERP analog transmitter.

But there is no reason why low VHF cannot get up to say 100 kW

ERP rated the way digital is. Sure, the power bills would be the same

as a big UHF station: but it would work great!


Doug McDonald
 
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