The FCC’s official predictor is at http://www.fcc.gov/mb/engineering/maps/. This service uses the FCC’s internal engineering database, which has information about things like directional antenna arrays (where they are in use) and is terrain-sensitive.
The WLS fiasco is mainly WLS’s fault: they wanted to “go cheap” and not buy a new transmitter, but got burned. It was well-known that DTV performance in UHF is much better in general than in VHF, but WLS thought they could pull it off anyway. They were wrong.
Markxxx, I’ve read through the Part 73 regs on television and protection from interference, and the FCC’s order changing WLS’s primary allocation, and I’m pretty sure you’re pretty far off base here. What’s your source for your claims?
WLS-TV’s transition plan, as decided by WLS, was to operate in the pre-transition phase on analog 7 and digital 52. The FCC would never have approved a post-transition allocation of digital 52 because 52 is a non-core channel that will be going away sometime next year, but as WLS’s intentions all along were to move to digital 7 in post-transition, the FCC approved WLS’s transition plan on that basis. However, WLS was required to run at reduced power to avoid interference with WOOD-TV in Grand Rapids, also operating on digital 7.
The FCC handles noninterference in television primarily by mandating a minimum distance between stations and by limiting station power. A station may petition for a variance from the station separation limits if, and only if, it submits to the FCC propagation studies that demonstrate that they will not exceed the technical standards in the rules, or if the other station(s) with which they might otherwise interfere enter into an agreement to abate or accept interference (and even then the FCC can refuse the waiver if they feel doing so is in the public interest). The separation limits would not have allowed both WOOD-TV and WLS-TV to have channel 7 at the same time; however, WLS-TV agreed with WOOD-TV to modify its operational parameters so that it would not interfere with WOOD-TV within WOOD-TV’s served area (Grand Rapids). The problem is that those parameters resulted in performance inadequate for Chicago’s “urban jungle” environment (a problem which has been seen in many other communities where DTV stations trying to operate in VHF-Hi have been unable to achieve the results they had hoped for with their new power limits). This was actually predictable, but many of these stations (including, apparently, WLS-TV) chose to ignore that in the hopes of saving some money.
So WLS-TV, upon going live, discovered that they’d lost a substantial portion of their viewership. They quickly petitioned the FCC for permission to move to digital 44; said peition was joined by WOOD-TV (who would then be relieved of its obligations to limit its operations so as not to interfere with WLS-TV) and was quickly granted. If WLS-TV had not elected to use a non-core digital channel as its pretransition digital channel, they wouldn’t have had this dipsy-doodle, but the decision to use a non-core channel was itself founded entirely on WLS-TV’s desire not to buy a full-power UHF transmitter, rather than any specific “errors” made by the FCC.
WLS-TV is still entitled to exactly as much protection from interference on its new allocation as it was on its old one. In fact, they’re actually entitled to more protection because there’s no nearby channel 44 stations, and they’re now allowed the full power permitted for a station operating at the antenna height that the Big Willy offers. I don’t know where Markxxx is getting a lot of his comments above, but I can’t find any way to support them in the regulations or the papers filed with, and orders granted by, the FCC in this matter.
Complete and utter crap. Not only that, but you don’t need a special digital antenna some people are pushing.
Go to http://www.antennaweb.org which will help you pick out the type of antenna you need and help you know where to aim it. I got a new antenna from Denny’s Antenna Service which is some small shop in Ithaca Michigan (they sell over the Internet). I went to them because he was one of the few places that was not trying to sell me a special digital antenna. Plus, he was one of the few stores that listed their antennas by the ratings of the CEA-certified Antenna Mark for Outdoor Antennas. (It’s the only way you can really tell if the antenna you’re looking at will work in your area).
We got rid of our cable, got an antenna, and are saving about $100 per month. We originally had a triple play package from our cable company (Cable TV, Internet, and phone), but the price went up to $160 per month. We kept the Internet service ($50/month), switched to T-Mobile@Home ($10/month) and dropped the cable TV.
No such thing as a digital antenna. Antennas pick up radio waves and don’t care how they’re structured.
The problem with digital TV signals is that there’s no degradation. You either have it or don’t. With an analog signal, you might get a lot of snow, but you’d get a picture, and many people have gotten so use to the snow, they never realized how bad their picture was.
Go to http://www.antennaweb.org and find out the size of the antenna you need and where to aim it. It saved me a lot of trouble when we switched to digital. One of the problems in a city like L.A. is that tall buildings will block your signal. However, if you go to the Antenna Web website, you can get pretty good aiming directions.
Your not-so-local RadioShack checking in here… Since the digital transition, recieving over the air TV has been a lot harder than is used to be. Many people, especially the elderly have been given to believe that a converter box will put them right back where they were before the transition and that’s simply not true in many cases. Also, plenty of unscrupulous electronics sellers made their fortune selling “digital ready” and “digital capable” TV’s, neither of which actually means “has a digital tuner it it.” Don’t get me started. Often people need to do more than just get a converter box to recieve the same channels they used to. The reason for this is that DTV propagates differently than analog did. Part of that is just the nature of the signal. Analog could take some signal loss and maybe come in with a little ghosting or fuzz. Digital has a great picture but the ENTIRE signal has to get there in one peice. We give the general guideline that TV stations effectively transmit about half as far as they used to and the average customer will recieve about half as many channels as they used to. Its certainly true you don’t need a “digital” antenna, excepting that some VHF channels are actually now broadcast on UHF, so if you had a VHF antenna only you’ll lose alot. That said, in many cases the rabit ears, cheap RG-59 coax and other old gear won’t cut it for digital. Many people who recievced a satisfying number of channels with an indoor antenna now need a rooftop to get a similar amount. Most frustratingly perhaps, over the air TV has a big demographic that’s older and less tech savvy making it hard for us to know wether they’re properly set up. Very hard to troubleshoot from afar.
I’m in southern NH, with our one lonely network station, WMUR. They’ve redcuced power significantly, and most people around here watched the Boston networks. We’ve had to tell a lot of people that receiving Boston TV is all but impossible now, and many people even very close to the WMUR transmitter can’t get it. Don’t shoot the messenger.
Don’t ya’ll knock the shack too much. There’s great knowledgeable people and some not so much like anywhere else.
+1 for antenna web, good info there. Your gubbermint is here to help you too, at dtv.gov with some good reception maps.
Digital TV signals do not “propagate differently” than analog TV signals. Propagation of RF signals has absolutely nothing to do with how the signal is modulated. The only thing that would change how the signal propagates would be if they switched the polarization of the transmitting tower from horizontal to vertical (or vice versa), and they’re not going to do that.
Digital TV has a far lower signal-to-noise requirement than analog TV did. The minimum signal strength for a “receivable” signal, at the receiver’s antenna, for analog TV in UHF is 64 dBuV/m; the comparable signal strength for 8VSB digital TV is 41 dBuV/m. In other words, you need about 1/200th the signal that you would have needed to receive good quality analog TV in order to receive digital TV. This has nothing to do with propagation; it has to do entirely with how the signal is encoded at the transmitter and decoded at the receiver. The flip side of this is that if you’re 10 dBuV down on analog, you still get something that is mostly viewable, but if you’re 10 dBuV on digital, you’ll get nothing, because of the way the respective encodings work.
If the FCC had allowed stations to simply switch to digital at the same operating powers they were using before, digital stations would be blasting all over the place and people would be receiving stations they’d never heard of; most stations would have seen their operating footprints double or more than double in diameter. Unfortunately, this would also have created a great deal of interference, with many viewers receiving two or even three stations simultaneously on the same frequency, and with the 8VSB modulation used for digital TV that would have probably resulted in no viewable signal at all. Therefore, the FCC reduced the authorized power of virtually every station by a substantial amount, typically from 20% to 90%. The FCC used propagation simulations to set a power level for each station that resulted in a viewable footprint substantially similar to their previous analog footprint. This simulation used the assumption of an external antenna mounted at 30 feet above ground level. You’ll find that most of the people who are complaining about their DTV reception are not using an external antenna mounted at 30 feet above ground level. The FCC’s modeling did not take into account people who would have been receiving a good quality analog signal had they been using an external antenna at 30 feet, but were instead receiving a marginal signal using an internal “rabbit ear” antenna. Such combinations will not work with digital.
The long and the short of it is, if you want to receive digital TV and your analog signal wasn’t crystal clear before, you will need an external antenna. Go out and buy one and install one: they’re not that expensive, and federal law guarantees you the right to install one in most situations, no matter what your landlord, homeowner’s association, or county zoning board says to the contrary.
KellyM’s right, I dumbed down the definition of PROPOGATE a bit. I’ll stand by my statement that given equipment as a constant, the average DTV station only effectively reaches half as far as it used to and the average customer only recieves about half as many channels as he used to.
All my stations came in better with the switch to digital. I use a simple dipole antenna. The one spot in my house that is fussy gets a loop in the antenna. If I bothered to hook up a roof antenna I would be pulling stations that I could never get with analog. Most of them are duplicate networks so there isn’t much point for me. I have some old antennas that I may try in my attic but I don’t plan on mounting anything on the roof.