Anablog

Digital TV (DTV) was to be fully implemented today when all analog stations were supposed to go dark. Last week Congress postponed the date until June 12, 2009. I figured we should just switch, but there was a colorable argument that now that we know that DTV pretty much requires an outdoor antenna to get all the same stations, probably with a rotator to boot, it makes sense to do the transition in the summer when the roof will not be covered in snow. The mainstream media seems to get it finally, with a nice article over at LA Times about how the reality of digital TV does not live up to the hype. ABC News had an article last week that pointed out that all the little portable analog sets used during disasters will no longer work and nobody seems to consider that aspect of things. I have gotten a huge report about DTV in the San Francisco area done by Louis Dorren and Noland Lewis, two ham radio operators. One gets 15 analog stations and only three digital stations, even with a good antenna. Turns out he lives on the peninsula between San Francisco and San Jose. He has found a whole strip going down the peninsula where Mount Bruno shields the delicate DTV signals emitted by Mount Sutro, the main TV tower in San Francisco (part 1, a 6 meg pdf, and part 2, another 6 meg pdf). The analog stations would punch over the hill but he can’t get any digital stations from Sutro. He lives 11 miles from the tower. Both authors are EEs and one invented the FM quadraphonic broadcast standard. Sometimes the report seems a bit too strident, even for an FCC critic like me, but they are basing their opinions on a series of field strength measurements made with a bunch of friends. Some excerpts from the report:

During the preparation of this report, it became clear that the ATSC DTV system did not undergo critical signal propagation studies. The result of the oversight is a system with extremely poor coverage capabilities.

As analog TV signals get weaker, and because they are Amplitude Modulated (AM), the picture displays noise, which is often referred to as snow. The sound in the analog TV system, which is Frequency Modulated (FM), generally stays good with little or no increase in noise as the signal get weaker. The DTV signal, which is 8 Vestigial Side Band Amplitude Modulation (8VSBAM), has a completely different characteristic as the signal gets weaker. It maintains picture and sound for a shorter distance from the transmitter. When it approaches the signal contour of the station, the picture begins to pixelate and the sound begins to stutter. If the distance is increased by just a small amount the picture and sound completely disappear.

The antenna situation with DTV is quite critical. Even though it has been touted that you can receive DTV stations with rabbit ears, that really only works if you have a good unobstructed path between your rabbit ears and the transmitter. In fact, with the indoor antennas I tested you have to be almost on the transmitter site’s doorstep.

Now comes digital television and for the first time compatibility is left out in the cold. The ATSC group decided that nobody will object to buying a new TV or at least a low cost converter box for their old TV. They then set out to throw all of the competing DTV proposals into a blender and pour out the “Grand Alliance System”. This system is one of the biggest Rube Goldberg concoctions, with such complexities that only effective production could be done using advanced Large Scale Integration (LSI) chips to make a “cost effective” DTV receiver. The signal transmitted is so complex that it can have up to 1/3 less propagation capability than the current analog TV signal.

What I found interesting was when they talked about how the FCC commissioned a report that (surprise) showed that DTV coverage was better than analog. The authors maintain that the company that did the study just took the effective radiated power (ERP) and the polar pattern of the transmitting antenna and assumed the transmission was on flat ground. The authors and their friends actually drove around the San Francisco bay area with an antenna and spectrum analyzer and characterized the signal strengths of analog and digital TV. As you might suspect, the digital TV signal reception area is actually much smaller, with some areas, like the peninsula, getting very poor coverage. It is obvious that the big corporate interests in the Grand Alliance, the consortium that came up with the DTV standard, was more concerned with inveigling their patents into the scheme so they could collect licensing revenue, rather than provide a robust system that was equivalent to previous coverage. Even more irresponsible, there is no backward compatibility like when color TV was invented (and the patents put into the public domain by RCA, under threat of antitrust action, so everybody could use them).

I asked the authors why my buddy Alan could get 40 stations with the giant antenna on his roof and they verified he was living in an area of San Jose that has good coverage even up to Sacramento. Like most things, some people win and some lose. I will reproduce two great spectrum analyzer plots from the report below. Gosh those old TV engineers were smart. Note how the analog signal has a lot of power in the sync pulse and the audio, so that is may it may get snowy in weak reception areas, but the picture will not roll and sound is still perfect.

This is the spectrum of an NTSC TV transmission; note the high power in the sync and audio.

This is the spectrum of an ATSC DTV signal. This is why the signals do not propagate as well as analog signal as well as being more prone to multipath and interference. The cliff effect is a function of the fact that the entire bit-stream must be perfect or the picture and sound disappears.

Now that we are entering a second go-around with this transition I hope the education will be a little better. One big thing that people may not understand is that all the digital channels are already working, it is not like they will have no use for the converter box until June. They can receive all their TV stations in digital today, and figure out if they need a better antenna and a rotator before the big rush in June. It seems like the media is picking up on my previous complaints. We need to convey that if your TV has an ATSC tuner you don’t need a converter box. Some TVs were sold with legacy NTSC tuners and called “digital ready” since they had 1024x768 resolution. Let us hope there is a special rung in hell for those TV marketing people. I also see some spots that stress that you still need an antenna; the signals do not come out of the converter box. Also you don’t have to worry if you only use cable or satellite, but it turns out many people seem to have an old analog TV in the bedroom or den, so you may have to deal with that. I have read there are about 50 million sets and about 17 million people that only have analog with no cable or satellite.

Real-life TV engineer Robert Getsla also sent a couple links about digital TV and the white spaces proposal that will put wifi transmitters into the “empty” TV channels. Interference to DTV Reception by Charlie Rhodes, and White Space: Group Warns FCC of International Consequences. Also another Charlie Rhodes article about white spaces, What I Know About the Great White Spaces.

OK so tell granny and all your non-technical friends that they can convert to DTV today. All the stations are already broadcasting digital, it is not like the DTV starts on June 12, it is just that the analog broadcasts will stop on June 12. Also be aware that the station number and the frequency it is really broadcast on has no relationship. Be aware that on June 17 2009, some stations will change frequencies, but we will still tune to the same channel number. Your reception will hopefully improve with the different frequency but it may get worse. The big pdf report above talks about using signal boosters but remember, boosters only compensate for long coax cable runs; they cannot pull a weak signal out of the noise. These amps only add noise and reduce the signal to noise, so if your TV’s RF amp can’t pull the signal out of the noise, a booster amp will not help.

OK, the only thing the mainstream media is really getting wrong is the reason for switch to digital. They are saying it is to make room for emergency signals or to improve reception. Like all things, the reasons are complex and interconnected. Firstly a decade ago the United States was way behind Japan, who was already looking at high-definition TV. The FCC was under pressure to get a system working in the US, but they took a very passive role, turning things over to the Grand Alliance. The grand alliance was made up of multinational corporations who put their patents and licensing revenue way before the public interest. In fact, they put their revenue in direct opposition to the pubic interest. No surprise there. Unfortunately the FCC allowed the Grand Alliance to discard backward compatibility in the modulation scheme. Several of the members were TV manufacturers, remember, so obsoleting every single TV was a great marketing ploy. The FCC wanted to issue coupons to pay for a converter box but the cost of the converter box is rarely covered by the 40-dollar coupon.

The FCC’s next problem was getting all the TV stations to sign up. Sure the FCC could just force things, but instead they made sure the digital TV modulation scheme could provide for up to 5 channels in the same bandwidth as one old analog channel. This way the FCC could lure the broadcasters to support the proposal since what broadcaster would not want to have 5 channels where they had one? Indeed some of the FCC claims that DTV has more coverage is based on the fact that if you live in a good reception area you may have more channels. So the metric of person-stations may go up but there still may be a million people that lose at least one station, or maybe all of them.

OK. So now all the multinationals are at the feeding trough and the broadcasters are signed up. The next thing that happens is that the cell phone companies point out that the FCC could also just juggle around the stations and push them all off channels 70 to 83. That allowed the FCC to auction off that bandwidth last year for 17 billion dollars. Next they will auction channels 52 to 69 after June 12^th for many billions more. So now the cell phone people have more bandwidth, the government has billions of dollars, and the lobbyists were really smiling. Next thing you know, the brainiacs at Intel and Google convinced the FCC that we could have a wifi network with fairly powerful transmitters and receivers all over the place that use the unused TV channels. Since the FCC would not auction the spectrum, it was more a way to look populist while screwing the cell phone people that just paid $17 billion for their slice of the pie. By now the broadcasters were realizing they were the runts of the litter in the feeding frenzy, and that DTV has crappy propagation and the cliff effect. They also must have realized somewhere along the way that you can’t really broadcast 5 channels at once since the compression will be so severe that the picture quality will look like crap. The interference that the white-spaces devices may cause are also a broadcaster concern.

Of course the ATSC standard was purposely complex, providing for all kinds of different resolutions, the multiple channels, and all kinds of audio options as well. This way only a giant multinational semiconductor company could make the chips for it and they could be sure to get a nice hefty price premium. In short everybody wins, except the public.

• The TV makers are drooling since your old TV won’t work and they can sell you new ones.
• Converter box companies are drooling since they can charge you for a box while getting a 40-dollar handout from the government.
• The broadcasters are drooling since they get 5 stations where they used to have one.
• The FCC is drooling since they can auction off the UHF upper band and make billions of dollars.
• The cell phone companies are drooling since they get some sweet good-propagating bandwidth to charge you up the whazoo.
• Intel is drooling since it can sell white-space chips.
• Google is drooling since they can deliver content over a new free bunch of bandwidth that is snuck in between TV stations.
• The semiconductor companies are drooling since the ATSC chips are so complex is assures a giant profit margin.
• The cable and satellite companies are drooling since many people will just give up on broadcast TV and sign up with those services.

And the people, well we are not drooling since we have a red rubber ball stuffed in our mouth while the government and the big corporations go medieval on us. Remember, when the phone companies have to pay a fortune for that spectrum they have to charge you a lot for service to make up for it. It is really a hidden tax, which happens to be unconstitutional, but that never stopped the government before.

I really feel sorry for the technical people at the FCC that have worked so hard for decades to reduce interference and insure good stewardship of the airwaves. Once the big money from the old analog cell phone auctions came into the picture, the FCC got a political crust that rules over the technical folks. I guess I might feel sorry for the cell phone companies that got chumped when the FCC allowed wifi white-spaces after the cell phone companies paid billions for the C-band, but I have a hard time crying for that crowd. And I do feel a little sorry for the broadcasters, who got sold a bill of goods over DTV and then got screwed yet again when the white space proposal got accepted last year.

What to do? Well, buy a big rooftop antenna and a rotator and heck with the cable and satellite people. You can use the antenna for communications when the economy collapses and we revert to the inevitable dystopian future. And don’t feel bad that our government is in partnership with big business to screw us, just remember Frank Zappa’s immortal words:

You say yer life's a bum deal 'N yer up against the wall?

Well, people, you ain't even got no kinda deal at all.

Cause what they do in Washington

They just takes care of Number One

An' Number One ain't you. You ain't even number two.

And yes, notice the double-entendre of the words “number two”. Gosh I love Zappa. Oh, and a shout-out to all the folks that helped Dorren and Lewis with the giant DTV report I talk about above:

Bill Domitilli

Bill Mariani KF6ZVJ

Bob Kellejian

Bob Sabo KE6CFG

Mike Flaherty WA6UBW

Nadine Trefz

Paul Stebbins

Tim Ahrens WA5VQK

Tom Watson WA6HCW

Randall Gawtry K0CBH

Stephanie Allan

These folks did an incredible amout of work because, like most engineers and technical people, they want to make your life better, not rip you off.

PS: San Francisco station channel 20 KOFY announced they would go dark today even though the transition date got pushed back. It is expensive to run two transmitters. Maybe I will call them later in the week to see how many complaints they get.