Editor's note: We are posting this story from our June 2005 issue because of the upcoming February 17, 2009 deadline for switching to digital TV, which may be hitting some snags.

Keep the antenna level. Rotate it 90 degrees. Move it a few inches to the left. Stand to the right. Hold it a bit higher...there—nope. Try again.

That has been my high-definition television (HDTV) experience. I plunged into the alphabet-soup world of digital television (DTV) in 2003, shortly after I replaced my electron-gun boob tube with a 42-inch plasma fl at panel. I hoped to enjoy beautifully crisp images—only to see what a lousy picture my Manhattan cable company was piping in. The larger screen amplifi ed fl aws in the analog signals, which not only produced images muted in detail and color but also added faint lines and speckles, not to mention scratchy audio. I was too cheap to fork over the $15 monthly fee for digital cable, which included only a few HDTV channels anyway. So I decided to snag the signals over the air, just like the old days.

Local stations around the country are making the change to digital, thanks to a 1997 Federal Communications Commission mandate (see www.dtv.gov). To smooth the transition, the FCC allows broadcasters to deliver both analog and digital signals over the TV spectrum (channels 2 to 69). If you can get standard over-the- air television, the mantra goes, then you can get digital.

So I spent some $300 for a set-top box, the Samsung SIR-T351 HDTV receiver, and then rooted around in one of my storage bins for the right antenna. Broadcasters in my area beam DTV on the UHF band (channels 14 to 69), so I grabbed the outline bow-tie antenna. (Rabbit ears work for the VHF channels 2 to 13.) I laid the bow tie against my west-facing window, trying to catch the signals originating from transmitters atop the Empire State Building a mile to the north. I turned on the receiver and watched my TV screen flash to life—with a “No Signal” message.

Actually the problem was too many signals. Reception in cities is notoriously bad, because the broadcast bounces around as it strikes the tall buildings. As a result, signals arrive at an antenna along many paths and at different times. The receiver has to sort through this mess and figure out which signal to lock on to. It’s like trying to identify the real lightbulb in a hall of mirrors.

In analog TV, such multipath distortion shows up as ghosts. As a kid, I used to tweak the antenna continually and maybe even pound the top of our TV’s wood cabinet. Reception did not have to be perfect: I could still follow Get Smart through the multiply warped images.

No such luck with digital, which is all-or-nothing: if the multipath problem is severe, the tuner will not produce any image or sound whatsoever. The only recourse I had was fiddling with the antenna (plasma TVs are too thin to pound). I managed to pull in digital broadcasts of WPIX (channel 33) and WABC (channel 45) and only sporadically at that.

I had stumbled headlong into the problem identified in the late 1990s by the Sinclair Broadcast Group, based near Baltimore. The company conducted field tests suggesting that indoor reception may not be possible. The U.S. transmission format is called 8-VSB (for 8-level vestigial sideband), which is more susceptible to multipath distortion than the European system, called coded orthogonal frequency division multiplexing, or COFDM. The 8-VSB format requires less power to broadcast and packs in more data each second (19.4 megabits compared with 18.66 for COFDM)—useful for “datacasting” services. But 8-VSB did so poorly in multipath environments that Sinclair urged the FCC to switch.

Although my experiences echoed Sinclair’s findings, I figured I should give 8-VSB an honest shot with a better antenna. Based on posts on the AVS Forum, a consumer electronics board, I tried the Gemini Silver Sensor. Looking like a miniature rooftop Christmas-tree antenna, this indoor model is supposed to be a ghost buster.

6 Comments

1. 1. wfitz1964 07:23 PM 1/10/09

   I have also used HDTV over the air as well when I moved into my new address. I live in the san francisco bay area. We have a simular issues with multipath but it is the mountains reflect the signal and cause loss of signal. One recogmendation I would offer is to use a omni directional antenna which allows a greater swath of area to be recieved but if you are in a hole or a bad signal stegth area you need a high gain directional antenna. Here are some of my tricks I learned when I switched over to digital it was like going back to school. I lived in a area which had rotten analog reception but the digital worked perfectly after I used my tricks. Also digital can be amplified much better than analog that is trick 1 . Most amplifiers will amplifie 1st and 2nd and even 3rd order signals as well as FM and other trnsmissions . This chatter gives a limit how much analog signals can be amplified digital is a different kettle of fish . It rests with the reciever the better the better quailty of tv you will enjoy. Another suggestion is to ground antenna even if it is indoors and to use a active as well as passive power line filter. Some of the problems can be cused by living in a steel framed building this causes all sorts of multipath due to the fact that steel is a perfect mirror for Radio Frequencies. The auther probably had that problem. Another approach that I have used is to use alumin foil as a simplistic RF shield this realy works ! The more that can be shielded filtered and amplified the better quailty your picture will be . However there are bad and just terrible locations . You might have to pony up the cost of cable or teleco or satelite. I love my cable but in a pinch I do use my digital TV with a antenna. While analog is imperfect it is best for fringe areas because a picture is recieveable even if it has degraded that is analogs only advantage and that is part of the econmic devide. I have helped some people who are with out means to make the trnaistion to digital most of these people are either old and don't understand the technologies or are of limited means . Some of them sadly will be left behind because of the limitations of digital.

   Reply | Report Abuse | Link to this

2. 2. wfitz1964 11:04 PM 1/11/09

   Another point I also failed to mention is the frequency band that HDTV tv is tunning in to. VHF has much better reception because of its lower frequency and longer wave length which can be up to 200 miles given perfect conditions. This allows it to carry much longer distances and to follow the earths curvature. However all radio frequencies are not like AM or short wave they do not skip. Both UHF& VHF must have clear line of sight from the TV transmitter to reciever. That is the issue of multipath because there is a obstruction so a relected signal arrives at a latter time and confuses a digital reciver . In plain old analog it it just ghosts.
   
   UHF has some better advantages for bulding because of its shorter wave length and just goes thru buildings but its shorter wave length limits UHF to just 100 miles at best and more than likely just 60 miles.
   
   Most of the frequency re-allocation will place most HDTV in the UHF band not VHF band with its superiour range. This is to give emergency responders VHF frequencies for example channel 2 is at 54 MHZ (mega hertz MHZ used to be cycles per second). 2,3,4,5,6 are going to be reallocated but I believe it different for each metero area . In sf bay area ch 11 will be 12 ch 7 will be 7 but it is in UHF right now for HDTV. The rubb is people wanting old VHF channles to behave the same way in the new system and that won't happen becuse of the limitations of UHF.
   
   The solution I would belive is good error recoverey and digital tv has that but too a point. I think the people who thought this up felt this would save the day. That is the single limiting factor there is no crummy mode that would allow digtal to work even if the picture is bad like analog. That is digital undoing in my viewpoint it either works or it does not or the signal locks or unlocks . No fussy logic and it will not give some people much of a warm and fuzzy feeling knowing that digital is less forgiving standard.

   Reply | Report Abuse | Link to this

3. 3. arfnotz 09:06 AM 1/12/09

   " A special amplifier inside boosts only the electric field signal picked up by the antenna, Dotcast says, while ignoring other radio-frequency waves" Good luck. The problem isn't low electric feild, and the problem isn't out of band signals. The problem is signals of the same strenght and the same frequncy displaced in time, and the only answer is a more directional antenna, which means a larger antenna.
   
   Imagine your in a large, echoy hall. Someone sings a song, but you can't hear the words, only confused noise. That's what's going on here - self intereference. There really isn;t a good answer, exept the first one you mentioed - buy the $15 a month HD service.
   
   Clearly, we've reached the peak of a technology wave - every new service only makes things worse than they used to be. More expensive, less useful, more prone to failure - not a good trend.

   Reply | Report Abuse | Link to this

4. 4. wfitz1964 05:54 PM 1/12/09

   Thats not entirely true in what you are saying. ATSC uses MPEG encoding there is a clock embedded in the brodcast signal while it is true each echo is received the time the signal was transmitted is also recoded . In a digital set each frame is stored and then reassembled and time received is also recorded. Similar to IP protocol is to computers but in this cause you can guess time is limited to reassemble each frame of digital information. Each frame is a representation of the picture and the sound is pulse coded and also reassembled. So only the best frame is kept but this requires a large frame buffer and very fast custom built computers. In the start of digital TV this was very expensive. Costs have dropped and performance has improved but no full proof system exists unless better timing information was encoded into each frame. This in turn puts more overhead and takes up space limiting the amount of data that can be sent. There is a point where a compromise has to make because of digitals limitations. Analog has no limitation is this regard because you can receive a signal no matter how bad it is degraded but snow noise interference from local sources will ultimately limit analogs range that is why analog is better in fringe areas and digital is more problematic.
   Another point I didn't make is when the analog transmitters are turned off some stations will start using different transmitters this will make a difference depending distance
   Digital can there for show true representation of the picture because there are not artifacts like aliasing color saturation as in the older standard not distortion in the ways color are encoded into essentially black in white television. All this still underlies the old NTSC (North American standards committee# standard. Examples to fix this standard were VIR, use of digital and analog comb filters and digital tuners. All these efforts made the old standard much better but were band aids.
   ATSC #American television stand committee) is still young and there will be efforts to improve it. Unfortunately like myself a middle age unemployed former electronic tech has been dumped for the far more lucrative slave labor of the Far East. With that the loss of control improvement do happen but as part of industrial research not tinkering in the past. This is all done far, far away industrial labs cloaked in secrecy. Did you know that much of the improvement in television and computers came from armature radio or hams? With outsourcing of our country very few people even know or care how their TV works or computer works. I have become a high tech has been.
   .
   

   Reply | Report Abuse | Link to this

5. 5. _etabeta_ 04:43 PM 1/14/09

   It's a real shame that the US chose 8VSB modulation in favor of the rival COFDM modulation used by the DVB-T standard. 8VSB is technologically inferior compared to COFDM for various reasons, particularly because COFDM is much more tolerant to multipath and mobile situations. Another big advantage of COFDM is the possibility for broadcasters to easily create a nation-wide SFN (Single Frequency Network), with obvious advantages for the allocated spectrum. The decision by the FCC to adopt 8VSB in favor of COFDM was based on comparative studies that were made in a inappropriate manner, biased because of pro-8VSB lobbying, even though the majority of the broadcasters preferred the COFDM DVB-T standard. Once again the US is going to have an inferior digital TV standard compared to the rest of world, as already has happened in the past with the NTSC analogue standard, which is way inferior to the PAL standard in terms of picture quality.

   Reply | Report Abuse | Link to this

6. 6. wfitz1964 12:59 PM 1/15/09

   In some waysyour comments are right but I feel NTSC is still better than PAL in one aspect the autdio is FM while PAL is AM with its obivious limitations.

   Reply | Report Abuse | Link to this