Frequently Asked Questions -- DTV Allocations.Com

These are the channel assigned by the FCC for each TV stations to broadcast their digital signal on?

The analog allocation is the what the TV stations broadcast on now. For instance WBBM-TV broadcasts on channel 2 in analog and channel 3 in digital. The FCC envisioned a transitional period where the programming would be duplicated in analog and digital signals.

Most but not all, all analog stations broadcasting before 1997 that had an analog channel were assigned a digital channel as well. By having two channels it provides for a gradual transition and allows the engineers at each TV station to work out any bugs before analog is shut off for good

If the analog station signed on AFTER 1997 they were not issued a companion channel. They will be required to simply turn off their analog signal and turn on their digital signal. This is called a "flash cut."

In the United States low power stations such as "class A" channels, low power TV stations and translators do NOT have digital companion channels. However they can apply to have a digital channel. For instance WWME-CA Chicago, applied to move to Channel 39 for it's digital signal.

No it's not the channels that are different but only the methods of broadcasting the TV signal that are different?

Not really, the TV community was opposed to moving channels. After all channels are powerful branding and the station owners managed to get "virtual channels" included in PSIP. This means WMAQ-TV broadcasts on it's analog on channel 5 and digital on channel 29. But you can tune to channel 5 as the digital signal sends out not only a TV picture but instructions for all digital tuners to display channel 5.

There is one huge exception for this and that is if you get your tv over the air (OTA). For the above example WMAQ broadcasts in analog on channel 5 but in digital on channel 29. In this case if you were getting our TV OTA you would need a UHF antenna to pick up WMAQ, cause even though the PSIP will map the signal to channel 5 the actual signal will be on channel 29.

Brands of tuners are different and some have trouble when you live in an area where you can pick up two channels from the same area. For instance I know of someone in north Delaware. He can get channel 2 from Baltimore and channel 2 from New York City. When he runs a "scan" of his TV (a scan looks for available TV stations), on one TV he has he gets TWO channel 2. His TV reads channel two twice, once for New York and one for Baltimore. On another TV with a different brand of tuner, he cannot get EITHER channel. That brand of tuner will not allow two stations mapping to the same channel. So he has to type in channel 23 which is the ACTUAL channel WCBS is broadcasting on and Channel 12 the actual channel WMAR is broadcasting on to get them.

Another issue is sometimes the PSIP gets garbled. Usually by a mistake at the station's end. There for the signal will not map and come up empty. You will always be able to get the signal on the actual channel the TV station is broadcasting on but till they fix the mapping on the PSIP you cannot punch in the "virtual channel."

Digital broadcasting is a more efficient way of broadcasting, so by going from analog to digital signals the FCC could use bandwidth for other purposes?

Mainly cell phones, but there have been calls for other uses such as high speed Internet.

Full power TV stations are required to turn off their analog signals by February 17, 2009. However this only means they have to stop BY that day. The station may decided to end analog service earlier. This deadline does NOT apply to low power television stations.

As you can see by the maps, that is hardly the case. It was discussed very early on about completely abandoning the VHF band but his was soon discarded.

TV stations like the VHF band as it requires much less power to cover the same area. This is quite a considerable savings to the TV station in terms of electricity to power the transmitter.

By in large this is correct. VHF is divided into two bands: Low Band VHF which covers channels 2 - 6 and high band VHF which covers channels 7 - 13. Low band VHF stations are subject to a lot of interference and since digital is largely an "all or nothing" type of transmission it makes a poor choice.

Again the cost of transmitting is less on low band VHF and it is thought through future technology will overcome the interference problems. As you can see by the maps few stations have chose to use low band VHF stations for their digital signals.

In analog TV you cannot have TV stations on channel numbers adjacent to each other. Note that some cities have channel 6 and channel 7 or channel 4 and channel 5. These stations are actually NOT next to each other. For instance between channel 6 and channel 7 lies the whole radio band of FM radio.

Of course channel 13 (VHF) and channel 14 (UHF) are not adjacent either.

With digital TV if the TV stations are located at the same antenna farm (or their transmitters are close enough) they can broadcast on adjacent channels

Originally when the transition to digital was discussed it was assumed that all the TV stations would broadcast a digital TV signal in High Definition. Broadcasting digitally in high definition would take up the same bandwidth as single analog station. (By contrast in Japan they developed an analog high definition broadcast, but this took up as much bandwidth as SIX ANALOG channels)

As it was being discussed it was soon apparent that even if they did broadcast everything in high definition the cost would be too great. After all old TV shows like I Love Lucy, were not in high definition so they'd have to be converted. (Any show shot in 35mm film can be converted as 35mm film is better than the high definition standard).

So instead of requiring digital stations broadcast in high definition the FCC decided to let the TV stations decided to broadcast in high definition or a standard definition using a digital format. By broadcasting in standard definition the TV station had a LOT of unused bandwidth. In fact a station can broadcast ONE high definition show or SIX shows in standard definition.

So a subchannel is simply a TV station using it's unused bandwidth to broadcast additional signals.

First is cost, not only in terms of equipment but in terms environment. For instance I took a tour of NBC studios in New York City and they explained they use fake wood, cheap lights and low cost make up because when they broadcast in analog the results are good. This is due to the low definition. But when you use high definition it becomes very apparent you are using fake wood or cheap make up or dim lights. You need to buy the real things to make it look good. This all costs.

Second is a return on value. Is the news any better if the picture is clearer? No it's not. Is Seinfeld any funnier if it's clearer?" No it's not. So why bother paying to convert old sitcoms to high definition if it's going to cost and not make them any better.

If a station uses standard definition they can broadcast more shows and of course hopefully sell more ad time on those channels.

With the advent of PSIP this will allow each station to map to their analog channel so it made sense to stay on their digital channels since they already built a new transmitter for that channel.

Furthermore the FCC only guaranteed channel protection IF the station elected to stay on their digital channel

For instance WGN-TV broadcasts in analog on Channel 9 and in digital on channel 19. WGN chose to remain on channel 19. This means that WGN has the FCC assurance that if any other TV station signal (from either another channel 19 or adjacent channels 18 or 17) interferes with WGN's signal on channel 19, it is the OTHER station that will have to figure out how NOT to interfere with WGN. If WGN had elected to go BACK to channel 9, it would have to have accepted interference from other stations who had been assigned channel 9 for their digital signal and chose to stay there.

Most likely, in fact it's probable. In the late 40s, the FCC assigned TV stations far too close and this had to be corrected. For instance there was a channel 7 in Wilmington, Delaware. But there was also a channel 7 in New York City and Washington DC. Channel 7 in Delaware was later removed from Wilmington and Wilmington was given channel 12 instead. Other examples include Ohio where stations from Detroit interfered in Cleveland and most of the cities of Ohio had their original analog allocations shifted.

I personally doubt that channel 19 in Chicago and channel 19 in Peoria will work but we'll have to see about that.

I know since digital TV I cannot view WTTW-TV (PBS) which broadcasts in analog on channel 11, since digital TV station in Lafayette Indiana and other cities signed on. There are far too many lines of interference.

It's mostly but not entirely true. Since digital broadcasting takes a signal converts it to numbers and sends those numbers to your TV where they are reconverted to a viewable signal. So basically you either get those numbers and your picture or you don't get the number and you get nothing. There is a pixilation effect that means it is possible to get "sort of" a picture. But generally you will get a clear picture or none.

This comes from the fact that many older people who never had cable and live in areas far away will lose TV. You see channel 2 covers more ground than channel 7 or channel 14. This is why networks originally wanted low VHF channels. When TV was new it didn't matter that the signal you got was good, people were just eager to get ANY signal. This especially was not a problem when TV was in black and white. When color TV came in, poor reception became a bigger issue.

But basically many people had "grown up," with TV pictures that were less than quality and got used to it. Indeed in North Carolina one of the biggest problems in Charlotte was that it only had two VHF stations and people where watching poorer quality signals from Raleigh, Asheville, Greenville rather than buy a TV with a UHF tuner so they could get a local UHF channel from Charlotte.

These people may lose their signal because once the digital signal goes father out if you don't pick up enough of those "numbers" you can't translate them into a picture.

They can get a good idea but not until analog is shut off will the know for sure. Although all TV stations are required to broadcast at full power, some have obtained waivers from the FCC, to broadcast at lower power due to the cost. Also some TV stations have their analog transmitters in different areas from their digital transmitters. And some digital stations are using directional antennas to prevent interference with station broadcasting on analog (they will turn off the direction once those analog signals cease.)

In theory yes, in fact WCIU-TV used to map to channel 1. The FCC put a stop to this and now says that a station must map to their analog channel.

The FCC is permitting stations to identify themselves with their digital channel number if they choose and to map there if they also desire. So in theory, WGN-TV which broadcasts in analog on channel 9 and in digital on channel 19, could rebrand itself as WGN-TV Channel 19 and map to Channel 19 IF it wanted to, it remains to be seen if any station will opt for this.

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Yes, the FCC says only ONE of the channels or subchannels must be broadcast free to see. This has lead many to speculate that a TV station will broadcast the same programs. One in high definition which will be scrambled and must be paid for, and another in standard definition for free.

This is open to debate, technically it certainly is possible but many people say the high definition signal is visibly degraded if you try to broadcast more than one channel if using high definition standards.

Right now no, the cable companies are pushing the FCC not to require this. The FCC now only requires the "main" channel to be carried is so required. Since a TV station can either invoke "must carry" or negotiate with a cable company, some powerful TV stations are negotiating things like "If you want to carry the main signal, carry my subchannel as well." This works for stations like network affiliates and big independents like WCIU-TV channel 26 Chicago, but it all depends on the cable company and their desire to get the signal.

Yes, it must be able to broadcast the emergency broadcast alerts and must carry a minimum amount of educational programing. However the educational programing requirement is cumulative. For instance if the station has 1 main channel and 2 subchannels, that means it needs three hours of educations programing per week for each channel . That is 3 hours times 3 channels or 9 hours total. But if the TV station likes it can carry all the educational shows on one channel only.

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