DTV: A Few Tweaks Left
Stations, FCC working to solve VHF reception snafus
By Glen Dickson -- Broadcasting & Cable, 6/22/2009 2:00:00 AM
In this story:
West coast bias
WHDH Boston didn't expect to still be paying the electrical bills for two transmitters come late June 2009. Like many U.S. broadcasters, the Sunbeam Television station and NBC affiliate had already exceeded its original transmission budget when the government pushed back the turnoff date for analog signals from Feb. 17 to June 12. WHDH Engineering Director Jim Shultis looked forward to shutting down high-powered digital broadcasts on UHF Ch. 42 and launching digital signals on VHF Ch. 7, the station's former analog assignment.
But as of last week, WHDH was still running transmitters for both Ch. 42 and Ch. 7. And both were being used to deliver the station's digital TV signal, which many Boston viewers couldn't find on its new Ch. 7 home after WHDH made the switch on June 12 and began broadcasting at 29.7 kilowatts.
After receiving numerous viewer complaints, WHDH petitioned the FCC late on the afternoon of June 15 for an STA (special temporary authority) to resume DTV broadcasts on Ch. 42, and was back broadcasting a simulcast of its Ch.7 there at 1:12 pm on June 16. The FCC says the station can continue broadcasting on Ch. 42 until the reception issues on Ch. 7 are resolved, as long as that doesn't cause interference to other stations.
“We've received immense viewer feedback,” says Shultis of the relaunch of Ch. 42. “'Thank you for bringing it back,' that type of deal.”
WHDH is one of several big-market outlets, including ABC-owned stations in Philadelphia and Chicago, to experience significant problems with reception since switching to a VHF channel for their permanent DTV operations. According to viewer comments and interviews with engineers, many of these stations were received reliably on their former UHF assignments but are now hard for viewers to find, even for those with an adequate UHF/VHF antenna. On the other hand, there have been few complaints of significant reception problems from stations with high-powered UHF assignments.
The FCC has moved quickly to address the issue. Besides granting the STA to WHDH in less than 24 hours, it has also helped out another Sunbeam station, WSVN Orlando, and Schurz-owned KWCH Wichita by granting them power increases. It has also redeployed forces to Philadelphia and Chicago to help tackle reception problems there, and is discussing solutions including boosting power or installing a translator to fill in coverage to affected areas. By the end of last week, the FCC was scheduled to place engineers in Baltimore; Nashville; Raleigh, N.C.; Rochester, N.Y.; Orlando; and Richmond, Va., to help stations who have asked it for assistance, either with DTV consumer outreach or technical issues with signal reception.
Some of the problems with VHF reception are simply due to consumers not having the correct antenna; many antennas marketed as “HDTV-ready” are UHF-only. And the double-rescan procedure recommended last week by the FCC has solved the issue for some viewers in New York and Chicago. But in many cases, the reception problems are more severe in close proximity to the transmitter than farther away. That suggests the problem is less one of signal coverage than of signal penetration into urban dwellings such as apartment buildings, where many viewers rely on simple indoor antennas.
“Most of the viewer complaints have been within 10 to 12 miles [of the transmitter],” says WHDH's Shultis. “It's like we have distance—the people out 20 to 30 miles with outdoor antennas are getting us—but we have poor penetration. On Ch. 42 at 948 kW, which is just under a megawatt, we had so much better penetration. ”
Caroline Welch, program director for WPVI Philadelphia, says reception of her station's 7.5-kW signal on Ch. 6 has been random, with next-door neighbors and houses on opposite sides of the street experiencing completely different reception. But many of the problems for Ch. 6, which also suffers interference from FM radio stations, have been close to the transmitter site in the Roxborough section of Philadelphia.
“There is no definitive spot, which is part of what makes it a little more of a complex issue,” Welch says. “You can't just say, if you live here, you can't get it.”
West coast bias
Engineers say the fact that VHF DTV signals don't seem to be having as many problems on the West Coast is due to the different construction techniques used there compared to cities farther east like Chicago and Philadelphia.
“One of the things we've found is that with the same Ch. 7 in Los Angeles and San Francisco, there's not as much of an issue,” says WLS Chicago Engineering Director Kal Hassan. “You've got stucco construction out West, and the VHF penetrates well. But in the East you have a lot of brick construction and aluminum siding, and all of that is harder.”
WLS, which has also experienced DTV reception problems from viewers living close to its transmitter atop the Sears Tower, never had reception problems with Ch. 7 in analog, Hassan says. But while it used to broadcast analog VHF at 55 kW, it is only allowed by the FCC to transmit digital VHF at 4.75 kW to avoid interference with stations in Milwaukee and Grand Rapids, Mich.
However, simply boosting the power may not be a quick fix in every market. Engineers note that some consumers with amplified antennas have actually been getting too much power and are overloading their receivers, rendering them useless to tune any channel. Installing signal pads between the antenna and receiver, which dampen the power sent to the receiver, have solved reception issues in some cases.
“We don't want to rush to judgment,” says FCC spokesman Rick Kaplan. “What we're finding are problems with limited stations and limited markets, and each problem appears to be different. That's why we're going to stations when they've asked us to, to try to find out what the problems are.”
—John Eggerton contributed to this story
E-mail comments to firstname.lastname@example.org
The aftermath of the Digital Transition has confounded, angered, confused & bewildered millions of residents. The media reports on the massive DTV transition problems with its monumental switch, has been quickly swept under the DTV carpet. Millions of voiceless Americans are making their displeasure known. The WITW (what in the world) is going on w/ DTV is rising up. It has now been 20+ days and there are many who still cannot receive the channels that they have come accustomed to watching on a daily basis. Especially when told over the last 2 years that this transition was easy and seamless. Neither of which is accurate. If you do have reception problems try doing a double scan process with your digital converter box. It has been moderately successful for many. www dot twurl dot nl/22j6pl
DeeNice Rhodes - 7/1/2009 12:47:45 PM EDT
I know there's no such thing as perfection but the idiots who thought of this idea to start with should have come up with a process where antennas should never have to be used again, especially to attain a digital signal and it's been a revolving nightmare since this took place a few days ago. WLS-TV is now breaking up yet again today and I heeard they were granted a boost in power so Kal needs to get his act together and get this thing boosted once and for all. This should be called Disaster TV and TV should never have to be viewed like this with all these pixelation problems. Bring back analog!!!!!
Richard - 6/22/2009 7:40:42 PM EDT
I live in Chicago 3 miles NW of Sears Tower, I went from 16 analog to ZERO digital stations. I have the correct antenna, but it's indoor. I cannot have an outdoor antenna like so many other renters. My landlord says, if I can't get TV, get cable. Which I did. I resent having to pay for TV now, when a month ago it was free. Digital signals will NOT penetrate the dense buildings in cities like Chicago. It makes no difference what channel it is. DTV was put in to allow spectrum to be freed up. So we now have NO TV for poor people and MORE cellphones and wireless for rich people. Add to this I've written to every Chicago station and not one cared. Why? They don't want to run two transmitters.
Eric Post - 6/22/2009 11:36:49 AM EDT
Those indoor "Amplified Antennas" were never a good idea to start with. Any engineer can tell you that, "If there isn't a good signal indoors, no amount of amplification will make it any better. And, it usually will make it worse."
Additionally, it would have been a good idea to make FM Traps an integral part of all "DTV-Capable" antennas. This was almost universal in the older outdoor VHF antennas, prior to the smaller "Cable-compatible" tuners...and the idea that "no one uses antennas anymore, anyway".
Instead of a "tuning control" on rabbit ears, a better idea would have been to include a step attenuator control.
Also, I wish that every set and converter had a built-in, switchable attenuator, which would allow viewers to test their sets for headroom/margin. This could have been a rear-panel switch, or a menu function.
Ken English - 6/21/2009 11:47:34 AM EDT
While most DTV reception problems for the typical viewer can be solved by proper selection and installation of a quality outdoor UHF/VHF antenna system, one possible source of poor reception, I believe, has been overlooked. That has to do with antennas at the transmitting tower, rather than the viewer's receiving antenna. Very few viewers have any knowlegde of the concept of "beam tilt" used by broadcast antennas. The signal from a high-gain UHF broadcast antenna is in the form of a very narrow beam traveling parallel to the ground radiating 360 degrees around the antenna tower. Most broadcast antennas have a built-in "beam tilt", usually designed-in electronically, but may be combined with a physical or "mechanical" antenna tilt. The tilt is typically between .5 to 1.5 degrees downward directed in all 360 degrees for a non-directional antenna, usually .75 degrees. The downward tilt allows the signal to better reach viewers close to the tower, and prevents the signal from traveling beyond the horizon where interference with other DTV station signals could result. A physical tilt in one direction may be deliberately designed-in to achieve a directional antenna pattern.
Reception problems can occur, especially for distant "fringe" viewers, if a non-directional broadcast antenna has been inadvertantly installed with a physical tilt or a wind or a shifting of the antenna tower has occurred causing a tilt. Broadcast towers are typically inspected at least once a year, and a check of the vetical plumb of the tower is a part of that inspection. The vertical plumb of the antenna needs to be checked very accurately. A small error in the angle could mean some distant viewers in one direction will lose a DTV signal that should otherwise be strong and viewable when the broadcasting antenna is properly vertically installed. Of course, distant viewers in the direction 180 degrees opposite will get a bonus strong signal at the expense of the viewers losing their signals.
I believe this is happening to my DTV reception with a broadcasting antenna in Walnut Grove near Sacramento, California. Two UHF stations, KMAX 31 and KQCA 58, are multiplexed and broadcast from the same non-directional antenna on the same tower at 850 kW and 600 kW ERP, respectively. Nearly all Sacramento area DTV stations also broadcast from Walnut Grove towers. My DTV receiving location is in the Sierra foothills near Pollock Pines 59 miles from the Walnut Grove towers. I have a large, amplified outdoor UHF/VHF antenna system that receives strong, viewable DTV signals from all major Sacramento area DTV stations EXCEPT for KMAX and KQCA. KMAX should be the strongest UHF DTV signal at my location according to TVfool.com, a website that computes TV signal strength for all TV signals received at any selected location. I checked a discussion website, the AVS Forum, and found that the KMAX DTV signal is strongly received in San Francisoo, well above all other Walnut Grove signals. San Francisco is about 59 miles and exactly 180 degrees in the opposite direction from the Walnut Grove towers from my Sierra foothill location. A physical tilt to the broadcast antenna upward toward San Francisco would explain why San Francisco has a strong KMAX signal and my foothill location has a weak, often unviewable, signal. KQCA is likewise unviewable. Both KMAX and KQCA should have strong, viewable signals and are viewable when atmospheric conditions occur which correct the antenna tilt for brief time periods through atmospheric refraction.
I have contacted the broadcast engineers of both KMAX and KQCA and reported the tilt problem and requested that the vertical plumb of the KMAX/KQCA antenna be checked. Whether my request will be taken seriously and acted upon, I don't know. It is difficult for individual DTV viewers to be heard, even if they have degrees in physics and engineering as I do. KMAX and KQCA are licensed by the FCC for non-directional antennas. For the KMAX/KQCA antenna to have a physical tilt would make the antenna a directional antenna which is a violation of their FCC licensing. DTV stations need to pay attention to and take inspection of the vertical plumb of their broadcast antennas seriously and correct any tilt problems.
foothill dtv - 6/21/2009 7:55:31 AM EDT
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