Deconstructing Aereo

On April 22, the Supreme Court will hear arguments in the Aereo case. Broadcasters want the company’s unique “antenna to IP” service shut down, claiming it is avoiding retransmission fees by a clever legal/engineering system, and operates in violation of copyright laws.

Aereo and many other amicus briefs argue that Aereo is within its rights to deliver over-the-air broadcast signals to subscribers because each subscriber has, in effect, their own antenna and cloud DVR, which they control. In this interpretation, Aereo is only leasing space on an antenna to deliver a TV broadcast to subscribers, much the same way an electric company provides power to the home to operate a television.

There have been so many arguments for and against this service that it’s hard to keep up with them. Not only that, two U.S. district courts (1st and 2nd) have ruled in favor of Aereo, barring any injunctions, while a third (10th) has ruled against it, shutting down Aereo’s services in Denver and Salt Lake City.

In an unusual move, the United State Solicitor General has asked to present oral arguments in the case. This is significant because the Supreme Court often defers to the Solicitor General, who (it appears) is preparing to argue in favor of the plaintiffs (broadcasters).

You can find plenty of articles and coverage of the case, most focusing on the legal aspects and current copyright law. I don’t intend to discuss those, but instead will talk about a more obscure aspect of the case – the actual engineered antenna system, and if it actually does what Aereo claims it does.

Aereo Logo 300p

Before I get started, I want to emphasize that I have not seen the Aereo antenna system in person, nor any of the associated electronics. Nor have I had any conversation with company principals. (TechCrunch recently toured the NY Aereo facility and you can see a video of that tour here.) I only have photos of the individual antennas and the antenna array, and the patent applications to go by.

I should also mention my credentials to deliver the analysis you are about to read. I have been playing around with radio equipment since age 5 and actually had two pirate radio stations on the air – one AM, and one FM – while in high school, so many years ago. Not long after that, I studied for and got my first amateur radio license, and within 11 years qualified for the Amateur Extra Class license (KT2B).

Along the way, I spent hours building transmitters, receivers, converters, amplifiers and preamplifiers, and other gadgets, even etching my own circuit boards. At one time, I had a 65-foot antenna tower in my back yard with yagi beams for frequencies from 7 MHz to 2.3 GHz, and have backpacked homemade portable VHF/UHF/microwave stations into the Pocono, Kittatiny, Adirondack, Green, Berkshire, and Catskill mountains.

For about ten years, I wrote a monthly column on VHF/UHF signal theory and operation for the now-defunct 73 Magazine. I also contributed to QST and CQ magazines. When the digital TV transition started, I was the first person in my neighborhood to install rooftop antennas and set-top boxes to watch broadcast HDTV, and of course staged the infamous HDTV Super Bowl parties for ten years.

So I’d like to think I picked up a little knowledge about antennas and signal propagation during the past 45 years. With that in mind, let’s take a look at Aereo’s argument and the flaws I find in it.


To receive TV broadcasts, you need some sort of antenna. And that antenna can’t just be a paper clip or coat hanger (although both can work sometimes). The antenna must have some physical relationship to the wavelength of the signal being received. If it does, it approaches resonance and transfers the maximum level of signal to a receiver.

We know the relationship between wavelength and frequency. They’re inversely proportional to each other, and a quick way to determine the wavelength is to divide the frequency into 300. (Or vice-versa to determine the wavelength.) Example: The wavelength of a TV broadcast signal on channel 2, broadcasting at about 55 megahertz (MHz), is about 5.45 meters. If you could actually see the radio wave, one complete cycle of the signal would measure 5.45 meters, or almost 18 feet.

In order for our antenna to resonate – i.e., have gain at the desired frequency – it needs to have some fractional relationship to the wavelength. So, a full-wave loop for channel 2 would measure 18 feet. A  ½-wave dipole would then measure 9 feet, while a ¼-wave whip antenna would measure about 4.5 – about 54 inches.

That’s not to say that our channel 2 antenna wouldn’t work at other frequencies. It could also pull in signals at channel 3, or 4, or even 5 and 6. But it wouldn’t be as efficient at those frequencies as it would on channel 2.

The same principle holds true for high band VHF channels (7-13). To pull in channel 7, broadcasting at about 176 MHz, we’d like to have an antenna with a full wavelength of 5.6 feet. A ½- wave antenna would then measure about 2.8 feet, and a ¼-wave whip antenna would measure about 1.4 feet, or 17 inches.

For UHF TV channels, let’s pick 600 MHz (TV channel 36) for our example. A full wavelength here is 1/2 meter, or about 19 inches. A ½-wave antenna would then be 9.5 inches and a ¼-wave whip antenna, such as you’d find on wireless microphone systems, would measure slightly less than 5 inches.

Again, that’s not to say the ¼-wave or ½-wave antennas mentioned wouldn’t work on higher or lower UHF TV channels. It’s just that they’re most efficient at 600 MHz. All of this is just basic physics and innate knowledge to anyone who has worked with RF antenna and transmission systems, amateur or professional.

Each individual "antenna" in the Aereo system is about the size of a dime.

Each individual “antenna” in the Aereo system is about the size of a dime.

Here is a cross-sectional view of the tiny antenna elements in place.

Here is a cross-sectional view of the tiny antenna elements in place.

Now, let’s look at the Aereo antenna. It’s about the size of a dime and resembles a small loop antenna. Just looking at it in a photo and keeping in mind the science you just read, it would be impossible for such a small antenna to have ANY resonance or gain on low-band VHF TV channels, let alone high-band TV channels.

Yet, that is precisely what Aereo seems to be claiming: One subscriber can activate one of these antennas to watch WABC on channel 7 in New York, or WNET on channel 13. And I don’t see how these tiny little pieces of metal can even work on UHF TV channels: They’re just too small.

Granted, if they were close enough to the transmitting antenna atop the Empire State Building – like a few hundred feet away – the signal levels would be so strong that they would “brute force” their way through the antenna system. But functioning as standalone antennas a few miles away? Not very likely.

Now, here’s where things get tricky and the boundaries between engineering and law become blurred. Aereo installs these tiny antennas in close-spaced arrays on circuit boards. Thanks to the laws of antenna physics, that close spacing guarantees that adjacent antennas interact with each other. That’s due to the principles of inductive and capacitive coupling.

And that means the thousands of smaller, individual antennas couple energy together to act like a larger antenna; one that will approach resonance and have some gain at the desired reception frequencies.

No matter how you switch the antennas, they do interact; it is simple science. And that appears to be the secret sauce behind what Aereo is doing: Creating large “virtual” antenna arrays made up of thousands of tiny, individual antenna elements that, taken together, make up a large, directional antenna array.

According to the patent application, the individual antennas can be switched on the fly to individual receivers, depending on which ones are in use and which aren’t. So the company can claim that each tiny segment of the antenna is actually a stand-alone antenna, assigned to one subscriber.  (Note that, in some earlier Aereo press releases and news stories, they do mention that subscribers can “lease” one or more antennas as needed to pull in a signal. )


Now, if all Aereo was doing was providing thousands of tiny antennas that actually interact to form a large, steerable antenna array, that would be interesting enough. But an Aereo subscription also comes with a “personal” cloud DVR, sitting on a server somewhere on Aereo property.

That means the following must happen for you and me to watch Aereo’s service on our iPhones. (a) A signal must be received from a TV station – say, WABC on channel 7 in New York. (b) That RF signal on channel 7 must then be demodulated by a receiver and converted from the 8VSB modulation format to a baseband video signal, or at least an MPEG2 stream with video, audio, and metadata. (c) The baseband video signal or MPEG2 stream has to be re-encoded or transcoded to MPEG4 H.264 for transport. (d) The H.264 signal is then encapsulated with IP headers and travels to your home network and device.

That takes a lot of hardware. In a conventional master antenna TV system (MATV), one or more antennas are installed on an apartment building or office and one or more amplifiers go with it to distribute the RF signals from the antenna to multiple users. Is this a public performance? From my perspective, no, as the antenna system is merely passing along whatever channels can be received with it. The end-user determines what channels to watch and when. This is a perfect example of a “rented” or “leased” antenna system.

In contrast, a community antenna TV system (CATV, or cable TV) uses large antennas to capture broadcast signals and subsequently demodulates then to baseband video or MPEG, then re-broadcasts them on the same or different channels with a new program guide. In today’s digital world, your cable TV provider has encrypted these local channels, meaning you must lease or buy a compatible set-top box to watch them.

That is indeed a retransmission and a “public performance” in the eyes of copyright law. The CATV company charges for its service and sometimes inserts local ads on those channels. So they provide not only a remote antenna system, they also add in a DVR service, their own program guide, and encryption.

This is why broadcast TV stations and networks have largely given up on the old FCC “must carry” rules and now demand a retransmission fee for their content, just the same way HBO, Showtime, and ESPN do. It’s today’s business model, and it is threatened by what Aereo is doing.

For Aereo to have a 100% true-blue, subscriber-controlled “antenna system,” they would need individual antennas, receiver/decoders, and encoders for every subscriber. That would amount to thousands of discrete pieces of hardware and an enormous capital outlay they’d never hope to recover at $8 per month. Their patent describes a way to assign each antenna to a separate tuner to demodulate the video stream to MPEG2. That might work fine for a handful of viewers. But what if 10,000, 20,000, or 100,000 subscribers are watching at once?

There’s a reason why cable TV companies use single receivers for each channel at their head ends: It’s the only cost-effective way to provide service. And they use multiplexers to route more than one IP video stream to customers for the same reason. It is a classic “one serving many” model and  a cash cow for the likes of Comcast, Time Warner, and Cablevision.

This diagram from the Aereo patent filinhg clearly shows that, at some point, multiple streams of decoded MPEG2 video programs are mixed together and transmitted from the rooftop antenna systems to the MPEG4 transcoders in the basement.

This diagram from the Aereo patent filing clearly shows that, at some point, multiple streams of decoded MPEG2 video programs are mixed together and transmitted from the rooftop antenna systems to the MPEG4 transcoders in the basement.

OK, so let’s buy the argument that Aereo uses a few receivers as needed for each subscriber to pull in TV channels and perform the usual RF-to-video-MPEG conversion. But then, according to their patent application, they combine multiple MPEG2 streams into a multiplex (or “mux”) to send them from the roof of the building to the basement for transcoding to MPEG4 H.264 and ultimately, transmission to each subscriber over an Internet connection.

Combining those MPEG2 streams is really no different than multiplexing TV channels in a piece of coaxial cable delivered to your home. Note that, unlike our MATV example, the TV channels don’t exist in their original 8VSB format. They’ve been converted (altered) to another format for delivery to the viewer.

Note also, in the area between the MPEG-2 Mux and Demux, the words “Antenna Transport (N x 10GBase)”. Here is where Aereo’s entire argument falls apart: You can’t receive an MPEG2 stream with an antenna; only a modulated RF channel. Calling a 10 Gigabit Ethernet connection that streams MPEG2 digital video an “antenna transport” is disingenuous. The signal has to be converted to a new format to travel over this part of the network, and as I just pointed out, it is now a bunch of MPEG2 video programs combined together in one stream for efficiency…just like a CATV or DBS service provider would do at their head end.

In contrast, an MATV system simply receives, amplifies, and distributes RF channels intact to two or more viewers. Those RF signals aren’t demodulated or transcoded – they are delivered in their original state to the viewer. The actual demodulation and decoding happens in each individual TV set.

What’s even stranger is that Aereo is now calling everything ahead of the mux an “antenna.” Horsefeathers! Antennas are antennas; receivers and demodulators are receivers and demodulators. Separate and distinct. That’s as absurd as calling a car an “engine,” or a house a “roof.”

For Aereo to truly provide the service they claim they do, they’d need individual hardware and software processing for every subscriber. No more than one TV channel could travel at the same time to a tuner, and no more than one video program at a time could pass to an encoder, especially not in a multiplexed stream. That improbable and wildly expensive set-up would be a true “leased” antenna and reception system, controlled by the subscriber.

If at any time TV channels, baseband video, or MPEG streams are combined together during the process, then it’s a a CATV system. Pure and simple.


Again, let me say that I don’t want to delve into the copyright and business model issues with regards to Aereo. I’ll leave that to the lawyers. Instead, I’m solely focusing on the science of what Aereo does, and to me, it’s overly clever engineering, attempting to re-define the term “antenna” and parse legal terminology.

Their entire argument for getting away with retransmitting broadcast TV content rests on those thousands of individual antennas, which as we’ve learned, unquestionably interact with each other and are separate antennas in name only. The rest of the system appears to be more conventional, with receivers, MPEG streams mixed together, and MPEG transcoding – just like a cable TV does, or even an IPTV multichannel provider, like AT&Ts U-Verse.

The puzzler is why the plaintiffs (TV stations and networks) didn’t pursue this technical angle more aggressively in the first place. In the first court case (2nd Circuit in NY), at least one judge (Denny Chin) called Aereo’s system a “Rube Goldberg” approach, cleverly designed to circumvent copyright law. He hit the nail on the head. There was some testimony from an RF expert at the first hearing, but either the testimony wasn’t presented correctly or contained technical flaws. So the copyright violation angle has been pursued exclusively  by plaintiffs since then.

The judge for the 10th Circuit in Salt Lake City, Dale Kimball, stated in his February decision that “Aereo’s retransmission of plaintiffs’ copyrighted programs is indistinguishable from a cable company.” Kimball got it right as well, as did the three-judge panel that subsequently upheld Kimball’s injunction.

And off we go to the Supreme Court next week. How will this case turn out? No one can say for certain, but the odds appear to favor broadcasters with the Solicitor General seemingly arguing against Aereo.

Stay tuned!