Saturday, February 14, 2009

RT Article: The DTV transition (from December 2007)

In this month's issue, I'm going to discuss the DTV transition, how is applies to you, and what you need to do to be prepared.

A brief history of television
TV got mass adoption in the US in the 1950s and 60s. In the mid 60s, color TV became popular. In the early days, there were 12 channels, better known as VHF (channels 2-13). After many TV stations went on the air, the FCC decided to add the UHF spectrum (channels 14-83), so that many other stations could go on their air, and translators could relay stations to rural areas where the signal was too weak to bring in a satisfactory picture. This is where the story of American TV begins.

The early days
Most households in the suburbs of a city were able to get good reception (at least on VHF channels) with the pair of rabbit ears which came built in with most TV sets in those days. If you lived out in the country, or wanted better reception than rabbit ears could provide, you installed an antenna outside. Often, people installed basic, medium range VHF antennas, and adjusted them to the best compromise of all channels. At the time, antenna rotators, pre-amplifiers, long range antennas, UHF antennas, and towers were all considered luxuries, and few people had anything better than a mediocre antenna setup which produced mediocre reception. As time went on more and more UHF stations hit the airwaves, but few people could get a good picture on these stations (because they only had a VHF antenna).

The advent of cable television
In the 50s and 60s, there were rural communities where TV reception just wasn't possible, due to the fact that the nearest stations were 150 miles away. While reception of VHF stations is possible at this distance, you would need a stack (two identical antennas pointed in the same direction) of long range antennas, a pre-amplifier and a large tower. Often, the TV & Radio shop in a town would put a tower on top of a near by hill and pipe in the signal to the community via a network of cable, and charge a nominal fee for access. This became known as community antenna television, or cable TV. By the mid 70s, cable systems were becoming popular in many cities, even those with adequate signal, because cable offered all your local channels with static free picture!! With the advent of satellite TV, cable companies started offering new networks, like CNN, MTV, etc... In the late 70s and into the 80s, most Americans made the switch to cable.

While most Americans hooked up to cable, country dwellers and TV enthusiasts alike were installing 8-12' (C-Band) satellite dishes in their back yard to get those same "cable channels." Not only did this lucky minority not have to pay for these channels (they were free at the time), but they were able to receive over 100 "cable channels" network TV feeds and a host of other assorted stuff with their $1,000+ investment. At the same time, this minority were investing in improved antenna systems. In this period, antenna designs had improved considerably, coax cable replaced twin-lead, good combination VHF/UHF antennas were readily available, rotators were cheap and reliable, and pre-amplifiers became standard equipment. Because of the better hardware, higher expectations of the consumer, and good installations, getting a crystal clear picture was the standard, not the exception for antennas. In the 80s, the FCC reallocated channels 70-83 for other uses, leaving the TV spectrum at channels 2-69.

While the large C-Band systems worked well in the early and mid 80s, most network channels start scrambling their channels, in order to charge people and cable companies to access them. While most cable companies, and some consumers bought legitimate boxes and payed for their access, there was a huge market for illegal descramblers that would decode all the channels without you ever having to pay the networks. As a result of this, and the advent of digital broadcasting, most C-Band broadcasts moved to a digital standard better known as 4-DTV. Another downside to C-Band systems is that you could only broadcast 24 channels per satellite, so one had to turn their dish constantly.

Around this same time (1995), mini-dish came on the scene. Mini-Dish providers used higher power satellites and digital broadcasting to beam "cable channels" down to customers with 18" dishes. Mini-dish providers also undercut cable providers, provided more channels that was available on cable, all with better than cable quality picture. Since mini-dish systems didn't provide local channels, there was also a renewed interest in antennas.

Digital TV
In 1996, congress passed a measure, known as the Telecommunications Act of 1996, which created a plan to switch all over the air broadcasts to digital by Febuary 17th, 2009. The bill also re-allocated channels 52-69 for other uses (leaving 50 channels, or ch. 2-51 for TV use). The standard being used for over the air broadcasts (known as the ATSC standard or DTV ), allows station to broadcast a data stream of near 20 MB/sec. This allows broadcasters to air a high definition channel, and a standard definition (DVD quality) channel at the same time. It is also possible for a station to broadcast five DVD-quality stations simultaneously. The standard also allows stations to broadcast their call letters, program guide information, audio only channels, the current time, closed captioning and 5.1 surround sound. Since most DTV stations are on a different channel than their analog counterpart, the digital broadcasts include "re-map" data. Because there stations can broadcast multiple programs on the same channel, each program has a decimal prefix. For example, the main program is on the .1 channel.

A station such as KTTC (NBC) in Rochester is broadcast in analog on channel 10. Their digital station broadcasts two programs, NBC (in HD) on .1 channel, and CW (in SD) is on the .2 channel. Without remap data, these would show up on your TV as 36.1 and 36.2, but the remap data tells the receiver to display them as channels 10.1 and 10.2.

Digital signals are considerably more robust than their analog counterparts. As a result, an analog channel might look fuzzy or might have ghosting, but it's digital counterpart might lock perfectly. When the signal level gets too low for a perfect picture, the audio will cut out sporadically, and little blocks of the picture will freeze (this is called macroblocking). The intensity of macroblocking can vary significantly. Sometimes, you'll see one or two errors every few minutes, all the way to having consistent macroblocking and intermittent sound.

What do I need to do to be prepared?
If you subscribe to cable or get you locals through satellite, you don't need to do a thing. The sattelite companies are all set, and most cable providers will either convert the local stations to analog, or upgrade everybody to digital cable. If you use an antenna to get you locals, however, that's a different story.

First, you'll want to make sure that all your TVs can receive a digital signal. If you have sets that can't, you can simply go out and buy a converter box for each of them. Some DVD recorders, DVD/VCR units, and satellite boxes already have a DTV tuner built in. Before you go out and buy anything, check out your current equipment to make sure you don't already have one.

You should consider if now might the right time to purchase a new TV, or whether you want to wait. You don't necessarily have to buy a flat panel, or even an HD set, just something with a digital tuner. If you want to keep your existing TV, consider whether you want to get a DVD recorder. A number of these units are in the sub $200 range, and are just the ticket to replace that aging VCR. If you don't need anything but DTV reception, then go ahead and get a stand alone converter box.

Next comes the antenna part. There are a couple of things consumers need to know. Most VHF-LO stations (ch. 2-6) will move to a different channel, come 2009, but most VHF-HI (Ch. 7-13) stations will keep their current allocations, and some UHF stations will swap around. If you use an indoor antenna, you'll want to evaluate whether or not you get satisfactory UHF reception, or whether you'll need an outdoor antenna. If you have an outdoor antenna, you'll also need to evaluate your reception. What do your VHF-HI channels look like? What do your UHF channels look like? Does the rotator work? Is the antenna falling apart? Do I need go fix/replace stuff in order to get good reception?

The DTV Converter Box Program
As of January 1st, 2008, the government will allow each household to request 2 $40 coupons to purchase a qualifying converter box. It's been speculated that these units will cost less than $100. After the 1st of the year, check DTV.Gov for more information about this. In my research, manufacturers are planning to sell the converter boxes for as low as $60, meaning it will only cost the consumer $20 to purchase (with the coupon).

Some resources to help you:
-The Audio Video Science Forum (, a popular Home Theater message board as an entire section of threads about local reception (the "Local HDTV Info and Reception"). Here, you can find out what setups worked for others, information about local stations, and post-transition lineups and issues, and local antenna installers. The HDTV Reception Hardware section of this Forum is a great place to ask about hardware,DTV boxes, etc... and are two popular TV reception prediction engines. These are useful in determining what you can get and what you need to receive it. TVFool is much more precise, but more technical. AntennaWeb is best used a second reference. Note: On the AVSForum, it's standard practice to post your TVFool results when asking for reception advice.
-The HDTV Primer ( is a technical, but comprehensive site on all aspects of HDTV. Their "Erecting an Antenna" section ( is particularly useful.
-If you need parts, has sells a wide range of antennas and supplies at good prices.

Quick troubleshooting for antenna
Problem: I get good VHF, but no UHF.
Check your TV. Is it set to cable or antenna mode (sometimes called TV). Set it to Antenna, then try again.
Is the pre-amplifier power supply plugged in (the power supply is a little box with two connections, one marked "to pre-amp", the other "to TV"). If not, plug it in.
Does your TV have separate VHF/UHF inputs (old ones do)? If it does, get a VHF/UHF splitter or connect the antenna to the UHF input.
Problem: Stations come in, but look poor.
Make sure your pre-amp power supply is plugged in.
Examine the antenna. Is it a VHF, VHF/UHF or UHF model? (If your unsure, ask on the AVS forum and post a picture of the antenna).
Try rotating the antenna towards the desired station (get the exact direction from

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