Last year, I moved. For many reasons, I did not subscribe to cable television. To save money and avoid wasting time watching bad TV, I decided to see how much I missed it. I purchased a $10 set-top antenna, positioned it as best I could, and waited to see if I suffered withdrawal symptoms from not having cable or a satellite subscription. Aside from missing The Daily Show, I was fine.
At first, I was only watching regular old analog TV. I live in San Francisco, and my home is only a few miles from Sutro Tower, the main TV transmitter for the San Francisco Bay Area. Although I'm only a few miles away, at least two hills block a direct line of sight to the tower, and my home is located in a valley of sorts. My regular reception was full of ghosts.
Some ghosts are worse than others. The very high frequency (VHF) stations, channels 2-13, come in quite well. Some channels have faint transparent ghosts, but it is almost imperceptible. The ultra high frequency (UHF) stations, channels 14-69, are noticeably worse because, with the exception of one channel, I lacked a direct line of sight. Digital TV reception became an attractive idea because the stream of bits can self-correct. If you have enough signal to decode, you get a perfect picture. The flip side is that if you don't have a signal, you get a blank screen.
As is often the case, external events intervened. KCSM, one of the PBS stations in the San Francisco area, lost the lease on their analog transmitter site in May. As required by the FCC, KCSM had been broadcasting a digital signal on channel 43 in addition to the analog signal on channel 60. When the analog signal went off the air, I decided to buy the equipment I needed to receive their digital signal. As a bonus, most of the other stations in the area were already broadcasting digitally, so I would receive clear pictures on all of the channels I watch.
Tinkering with electronics can become a great time sink, and this project certainly had the potential to develop into a multi-thousand-dollar sinkhole. To hold down costs, I decided to avoid upgrading my A/V system to high definition (HD). The cost of a TV upgrade would be tolerable, but I can no longer imagine living without my TiVo, and high-definition TiVos are still quite expensive. Upgrading everything to high definition is a much more complex project because I would want to get a DVR of some sort, possibly a media PC built around a card from pcHDTV.
There are many types of digital television broadcasting. My project was to receive terrestrial digital signals. The word terrestrial is used to refer to traditional land-based antenna broadcasts, as opposed to cable or satellite television. Terrestrial digital TV broadcasts have a whole new set of standards, defined by the Advanced Television Systems Committee (ATSC). Naturally, to receive digital signals, you need an ATSC (or, often, simply "digital") tuner. To get an ATSC tuner, you can purchase a set-top box with a tuner, or an "integrated" HDTV set that has a tuner built in. I decided to go with a set-top box because I wanted to keep all my other TV gear, and I wasn't quite ready to take the high-definition plunge.
Digital TV is more than clear pictures at standard definition. A standard analog TV channel requires a 6MHz bandwidth, which is a vast amount of spectrum for the data it carries. By chopping up the TV signal and transporting it digitally, the 6MHz bandwidth can be converted into a bit stream of approximately 19Mbps. That bit stream can be used to carry anything, though the most common use is to carry MPEG-2 video streams and associated audio. 19Mbps is enough capacity to carry multiple TV broadcasts; many stations use this capability to broadcast multiple "subchannels" within the assigned digital channel.
For example, KCSM's first subchannel, 43-1, broadcasts the TV signal; the second subchannel, 43-2, is a simulcast of their excellent jazz radio station. As it turns out, the radio station does not come in too well at the house, so converting to digital TV would also bring the radio station in. Subchannels may be unrelated content as well; Mark Cuban struck a deal with a Bay Area local affiliate to carry HDnet broadcasts on channel 4-2.
Many analog TV stations were given a second channel to broadcast digitally. (See the National Association of Broadcaster's channel map.) As an example, the Fox network affiliate in San Francisco was on channel 2 with their analog signal. Their digital TV broadcast is on channel 56. Rather than force TV viewers to remember that we need to go to channel 56 for the high-definition digital broadcast, though, a digital TV facility called the Program and System Information Protocol (PSIP) can "remap" channel numbers. Fox's Bay Area digital channel is broadcast in the spectrum for analog channel 56, but the PSIP data transmitted with the signal remaps the number to channel 2-1.
I have now owned a TiVo for approximately a year and a half, and I will not give it up. Standalone TiVo units are standard-definition devices, so I needed a set-top box to downconvert high-definition signals for them to be suitable for the TiVo and my existing standard-definition television set. A set-top box might also come in handy later, since many high-definition sets do not include a digital tuner, although recent FCC rules requiring digital tuners are beginning to take effect for larger sets. With a digital tuner, I could feed my TiVo flawless standard-definition signals to record, but recording digital TV off the air is not (yet?) a typical use case for the TiVo. There were three basic challenges I faced:
To receive digital signals, the TiVo needs a hand. External HD receivers will decode digital signals, and they can all downconvert a high-definition signal into standard definition for non-HD equipment. That much is straightforward, and can be served by almost any set-top box on the market. New HD receivers can be purchased for less than $300, but as is often the case, there were two additional features I wanted that are not common at the entry level.
First was the ability to output the video to multiple output ports, as well as simultaneous output of high-definition and standard-definition signals. If I were to upgrade to a high-definition set, I would want to watch TV in high definition, but I might still want to simultaneously record that program in standard definition on my TiVo. This is a common feature, but not well documented in product manuals.
The second feature is tied into the guide data. Digital channel numbers consist of a main channel number and a subchannel identifier, usually written with either a dash (2-1) or a dot (9.1). TiVo guide data does not include programming on all of the digital subchannels. In most cases, this isn't a problem, because there is only one subchannel, and it is an HD simulcast of the analog broadcast. However, TiVo's channel changing is not subchannel-aware. To use a TiVo to control a set-top box, the set-top box should automatically fill in a subchannel identifier of "-1". If the TiVo changes the channel to 2, the set-top box needs to interpret the request as a digital tuner request, and fill in the subchannel to change to "2-1". Again, many set-top boxes will do this, but not all will, and this behavior is also poorly documented in product manuals.
The third, and most important, feature is to get a set-top box that can be controlled by a TiVo. Set-top boxes can be controlled in two ways: either by an infrared emitter that emulates a remote control, or with a serial port. I had a preference for the serial port because of previous experience with somewhat flaky infrared devices.
With a little bit of investigation, I learned that the TiVo service does not really support terrestrial digital TV receivers. The TiVo database of set-top devices consists mainly of satellite receivers, while high-definition tuners are generally not supported. Many satellite receivers also include high-definition tuners, so I decided to look at the TiVo cable and satellite box compatibility list.
I began by searching the compatibility list for a receiver that could be controlled by the serial port, and started to narrow down the list. Eventually, by reading reviews, I learned that the LG LSS-3200A, Sony SAT-HD300, and Hughes HTL-HD offered everything I wanted. (All three units have identical hardware, manufactured by LG, though the prices vary.)
TiVos can select channels using the serial port, and will also provide simultaneous outputs and fill in a default subchannel identifier of "-1". There are tuners that are said to be better, but they lack the ability to be controlled by a TiVo. I purchased an HTL-HD from eBay, in large part because the auction price was much lower than its nearly identical LG and Sony twins. By running the setup program on it, I was able to configure it as a digital tuner without DirecTV service. The setup program also includes a channel scan that will identify both analog and digital signals.
The main downside to the HTL-HD is that it does not have a good way to select which channels are in use. If you (or a TiVo) repeatedly changes the channel to the same number, it will cycle through its inputs. If the number "4" is entered repeatedly, it can have frustrating results as the HTL-HD cycles through its inputs. The first time, it will go to the digital broadcast on 4-1, automatically filling in the subchannel. However, a second channel change will cause it to go to analog channel 4, even if it is marked as a channel that is not received. Even worse, a third consecutive request to go to channel 4 will change to analog cable channel 4, which is just snow in my setup, since I am not a cable subscriber.
Although I have no analog cable channels configured, the HTL-HD will accept requests to change to it because there is no way to remove channels from direct channel access requests. In the end, this is a minor frustration that requires manual intervention on my part. Because the first tuning request will attempt to find the digital channel, I will look at the To Do list once a week. If there are two recordings that will be on the same digital channel, I insert a five-minute manual "junk" recording on another channel between my two scheduled recordings. When the second program rolls around, it attempts to change from the junk channel to the target channel, and pulls in the digital channel again.
Once I obtained the set-top box, I connected it to my TiVo as a second input. A cheap set-top antenna was already used to receive over-the-air broadcasts. I connected the HTL-HD and its antenna to the TiVo's video inputs as a second input source, with the TiVo serial control wired to the HTL-HD for channel changing purposes.
Getting guide data was reasonably straightforward, though it involved deception. I lied to my TiVo and told it that I was a satellite subscriber. The "satellite" service is a set-top box that can pick up the TV broadcast, and the TiVo will simply record what is received on the S-Video input. To find the right "satellite" service for my guide data, I needed to compare the channel lineup for satellite service to the broadcast channel lineup. TiVo purchases guide data from Tribune Media Services, which also owns Zap2it. I put my zip code into Zap2it, and looked at the lineups from both major satellite providers, DirecTV and Dish Network. Both channel lineups are identical, except that Dish Network has KCSM on channel 60, its analog broadcast channel, while DirecTV has KCSM on channel 43, its digital broadcast channel. I selected the DirecTV lineup because analog channel 60 is no more.
For the most part, the guide data was complete. There were two major exceptions. One is that my "satellite" configuration work-around implicitly assumes that the digital channel is a simulcast of the analog channel. While usually the case, there is one notable exception in the Bay Area. KQED, another PBS station, has five digital channels, none of which match the analog broadcast schedule. I retained my set-top antenna, and I have continued to watch KQED's analog broadcast through the old antenna.
The second problem was getting guide data for KBHK, the Bay Area UPN affiliate. KBHK broadcasts analog on channel 44, and digitally on channel 45. Most stations will use PSIP to remap the digital channel number back to the analog channel number. If you tune to "2-1" in the Bay Area, the PSIP data will direct your digital TV receiver to go to the frequency assigned to channel 56.
For those of us who remember the analog numbers (or have TiVos), PSIP is vital. For some reason, KBHK has decided not to use PSIP to remap their digital transmission on channel 45 to 44-1. As a result, I am recording KBHK's analog broadcast as well. However, the antenna on the HTL-HD is better at receiving a clear picture, so I told my TiVo that it should receive channel 44 on the satellite. The picture is reasonably good (and certainly better than it used to be), though I would prefer that recordings on channel 44 switched the set-top box to the digital broadcast on channel 45. In the future, it is possible that the PSIP data will be modified to perform the mapping for me; in the meantime, I live with the analog reception, and if I notice a recording being made on channel 44, I will switch the HTL-HD to channel 45-1.
To work around the two problems with the guide data, I set up my TiVo to use both an antenna for traditional analog reception, and "satellite" for a digital TV set-top box. TiVo presented me with all of the channels in the lineup, and I configured it so that most of the channels were "satellite," meaning they come in through the set-top box because they are received digitally. For local broadcast channels, I selected them through the satellite as opposed to antenna, as shown in the left picture below. TiVo presents both channel lineups simultaneously, noting the channel as either an antenna or a satellite channel. I went through the channel lineup and selected all of the local channels as satellite channels so that they would be received digitally, with the exception of KQED. I left KQED as an antenna channel because digital 9-1 is not a simulcast of analog channel 9. The final lineup can be seen in the Favorite Channels display.
I ultimately decided to make channel 44 a satellite channel because the antenna hooked to the set-top box is better at receiving UHF signals than the old set-top antenna. There is a TiVo channel remap hack available, which I may try at some point on channel 44 and 45, but I set it aside in the interest of getting something running faster.
As the old saying goes, everything old becomes new again. In the case of television, it's certainly true. Digital TV signals are available at no charge over the air, and are only now coming to cable and satellite systems at an extra charge. Powerful external antennas are available for less than $100, and can deliver high-definition programming with no monthly charge. Many people have opted for a TV antenna for local channels because the quality is as good as a subscription service, but at no charge.
There are different types of antennas based on the frequencies that they are designed to receive. All an antenna does is to pick up electromagnetic fields and pass them down to a receiver. There is no such thing as an "HDTV antenna," in spite of the impression you might get from reading boxes. Different styles of antenna are required for VHF (55.25 to 211.25 MHz) and UHF (471.25 to 801.25 MHz). In most cases, the digital broadcast occurs on a UHF channel, and it is possible to get a UHF-only antenna to reduce weight, size, and cost.
The first step in selecting an antenna is to find out where you are relative to TV transmission towers in your area. The Consumer Electronics Association runs an antenna selection web site, which will give you a table of nearby TV stations based on your address, including distance and compass headings. Using antennaweb.org, I found that most of the digital stations near me were on Sutro Tower, though there were two transmitters about 35 miles south on a mountain near San Jose. Antennaweb can give you distance and compass heading to TV transmitters; an example is shown below for O'Reilly's headquarters in Sebastopol, California. Each line points at a transmission tower, and shows the channels available on it, while the corresponding table shows the distance to the tower.
In my case, my distance to the tower is less than five miles. A large antenna would certainly work, but I was hoping to use a small indoor antenna rather than undertake a large antenna mounting project. Indoor antennas are not frequently reviewed; the best write-up I found was written by Peter Putman, an independent consultant.
The first antenna I attempted to use was the Terk HDTVi. Although the Web is full of stores of bad experiences with Terk, it was the only brand carried at the first store I tried. I thought that my close distance to the transmitter would perhaps make up for shortcomings in the antenna. I purchased the antenna for $40, and went home to see how well it worked. It could receive one channel when I aligned the antenna with a compass, while the $10 set-top antenna I was using could get five. I did not investigate why performance was so poor, but I did return the antenna the next day. In retrospect, I should have known better than to purchase a product that claimed that its appearance was compatible with new TV equipment.
My next try was with a RadioShack 15-1880 internal antenna. A similar-looking antenna performed well in Putman's review, so I thought it might be worth a try. I pointed the UHF reflector at Sutro Tower, and checked for a signal on the digital channels. There was no signal on any of them, though my set-top box diagnostics did show a weak signal on each of them. I tried repositioning the antenna, to no avail. When I switched on the built-in amplifier, the signal vanished completely.
On my next antenna shopping run, I decided to buy multiple antennas and return what didn't work. (After all, any network engineer worth knowing instinctively knows that a windowed protocol is more efficient than a stop-and-wait protocol.) I picked up the Silver Sensor indoor antenna, and a Channel Master 3010 StealthTenna.
The Silver Sensor lived up to its reputation. It could get all of the channels from Sutro Tower, and it was not very sensitive to position, either. It even outperformed the StealthTenna, which a much larger external antenna. The Silver Sensor is even capable of pulling in a UHF station from 35 miles away, though it does require repositioning the antenna. Even though it is advertised as a UHF-only antenna, the signal on some VHF analog stations is watchable.
The only problem I had with the Silver Sensor is that its performance is somewhat sensitive to height. Once I had stowed my set-top box in a cabinet, the antenna was a few inches lower and did not receive channel 2. I tried a variety of boxes, but finally resorted to books to prop the antenna up to the height it was at when on top of the HTL-HD. I strongly suspect that the reason for the poor performance when placed directly on the cabinet was due to multipath reception indoors, and the small height change puts the antenna in a better spot. On September 12, the digital transmitter doubled its power, but the increased power did not seem to have any effect on the quality of the signal that I receive. It still drops out or pixellates occasionally. Unfortunately, the only solution to indoor multipath is to put the antenna in an environment where the signals won't bounce around as much. Practically speaking, that means mounting an antenna outdoors. For now, the minor inconvenience of a blip every hour or two is not worth the hassle of an outdoor mount.
The first phase of my A/V system renovation is complete. The TiVo functions as it always has, but it now receives a pristine standard-definition video input from the HTL-HD. The HTL-HD was an acceptable choice, though I wish its channel handling was a bit more configurable so it didn't need so much help tuning channels. Now that I've put a stake in the ground, I've already started to think about what I can do next.
In the spring, I will build an antenna system. Right now, I have to position the antenna carefully to receive the digital signal from channel 36, and the signal is spotty. Rather than rely on manual antenna repositioning, I would like to combine my existing internal antenna for San Francisco channels with a long-range UHF antenna for channel 36's digital signal 35 miles to the south.
For some reason, my remote-control situation has gone critical. Adding the HTL-HD threw another remote into the mix, bringing the total to seven remotes to control the A/V system. A single Harmony remote looks more attractive every time I trip across one of the seven.
Matthew Gast is the director of product management at Aerohive Networks responsible for the software that powers Aerohive's networking devices.
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