How well do dime-sized TV antennas (like the ones Aereo used) work?
December 10, 2014 4:59 PM   Subscribe

Just out of curiosity, does anyone know why no one sells a dime-sized TV antenna like the kind Aereo used in its datacenters? Or does anyone know where I might buy some? Or.. how well they work? (I assume they work since plenty of people bought Aereo's service and were happy with it... until it got shut down.)

Is there are good reason why dime-sized TV antennas aren't sold to residential consumers? I've tried a few "leaf" antennas the size of a sheet of paper -- and they kinda suck in my neighborhood. I orient the sheet one way and get some channels, and turn it 90 degrees and lose those channels and gain some others....

Is there a way I can set up an array of Aereo-like mini-antennas in my home that would allow me to get all the channels I can get (without having to buy one of those huge motorized antennas that rotate and need to be installed on my roof)?

Did Aereo need to have special signal processing hardware to go along with their dime-sized antennas? If so.. is any of that stuff available anywhere (besides the auction block from Aereo's bankruptcy)?
posted by lostguy to Technology (16 answers total) 3 users marked this as a favorite
 
From Gigaom:

"Aereo transmits from the top floor of a nondescript government building on Vanderbilt Avenue on the edge of downtown Brooklyn. You can see it on the right: Aereo building on Vanderbilt

Aereo chose this location for a reason. The floor on which it operates has a direct line of sight to the city’s biggest transmission tower. "

So part of it is that they had uninterrupted, fairly close-range (like a mile maybe?) line of sight between transmitter and receiver.

Also,

"Aereo CEO Chet Kanojia explained that the device is a simple copper antenna but that, rather than picking up the entire TV spectrum like a typical cable antenna, it picks up only the 6 megahertz block of spectrum that a viewer wants to see at a given time. He describes it as a “switched antenna” that’s beautiful in its simplicity. The ingenuity, Kanojia said, is that Aereo’s 1.5 inch antenna changes its electrical and magnetic characteristics in order to replicate the tasks of a standard 35 inch UFH or three foot VHF antenna."

I'm really not sure that this isn't bullshit. I mean, maybe it's not.

If I were you, I'd buy a normal omnidirectional antenna. Unless you have a very weak signal you don't need a rotating antenna really.
posted by GuyZero at 5:08 PM on December 10, 2014 [2 favorites]




I'm not gonna lie, I have no direct reason to think so, but I think aereo's line is bullshit. I sort of suspect they use one (or more than one, but less than one-per-person) good antenna and use the "one dime sized antenna per person" as a dodge. I dunno. Sounds paranoid when I type it out like that but the first time I heard it I busted out laughing. Sounded like bullshit to me.

(I am an electrical engineer, but I am not your electrical engineer)
posted by RustyBrooks at 5:35 PM on December 10, 2014


I'm really not sure that this isn't bullshit. I mean, maybe it's not.

2nd (former) EE here. Not YOUR EE. That part about changing electrical & magnetic properties of the antenna is probably true; it exists for other radio system designs today.

Radio waves travel through the air via electromagnetic propagation, and conversion back to optimal signal power by an "active" antenna depends on dynamically tuning the capacitive (electrical) and inductive (magnetic) properties of the antenna as a system to be resonant at the carrier frequency (TV channel) of interest. If the channel of interest changes at the receive electronics just beyond an "active" antenna, the tuning of the antenna has to be changed with it.

On the other hand, there are those complex, big, triangular TV antennas with a bunch of parallel elements converging to a point, also known as "log-periodic dipole arrays;" each pair of elements is a "dipole" antenna that resonates over a portion of the TV spectrum ... At a particular frequency the rest of the pairs do not resonate and are naturally out of the system ... So basically this is a different, "passive" way to solve the same problem.

Also, line-of-sight @ ~1 mile makes a huge difference.
posted by ZenMasterThis at 6:21 PM on December 10, 2014 [2 favorites]


... 'coz even though the elements in the "active" antenna aren't very large and can't capture much signal compared to the big antenna, the proximity to a powerful transmitter for each 6 MHz channel should more than make up for it, delivering acceptable signal-to-noise ratios despite its size.
posted by ZenMasterThis at 6:53 PM on December 10, 2014 [1 favorite]


I've always been skeptical of the antenna array concept as well, but I never took the time to dig into Aereo's line of patent applications. It's probably a great place to start looking into this stuff.

Deconstructing Aereo's Patent (tvtechnology.com) has an interesting perspective on the dime-sized thingy:

"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. )


So, a bit of subterfuge on Aereo's part about how the antennas relate to the individual customer, but also a better explanation of why you can't own a single gizmo and make it work properly.
posted by JoeZydeco at 6:55 PM on December 10, 2014 [2 favorites]


Oh and I missed the really important point before the above quote, regarding all those antenna packed into a dense array:

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.

posted by JoeZydeco at 7:04 PM on December 10, 2014


So if I understand correctly, each physical antenna is connected to one physical receiver circuit, but each antenna is tuned not for optimal self-resonance in isolation, but also considering the cross-coupling with/between the rest of the antennas in the array?
posted by ZenMasterThis at 7:05 PM on December 10, 2014


I'm pretty sure Aereo claims that they don't interact as one larger array made of smaller elements. But that's because I think their legal argument, such as it is, depends on it.

Keep in mind that they are trying to get around the redistribution problem (you can't record TV and play it back to N subscribers where N>1). Their claim is that when you sign up you get one antenna and one DVR allocated to you, i.e. its the same as if you had the DVR in your house, they just moved the DVR bit to their facility as a favor to you.

I don't think this legal fiction will end up holding up, but it's the core of their business model so they are sort of required to say that you get one antenna, regardless of exactly how true that is.

Antennas are not my field of expertise, and it's been 20 years since I even really learned anything about them. Technology is a wonderful thing and maybe they work exactly the way they claim they do, I dunno. Just sounds like marketing/legalese to me.
posted by RustyBrooks at 7:27 PM on December 10, 2014


If my last comment is correct, each receiver circuit is connected to one active antenna but uses all the other elements the other active antennas in the array as its own (sort-of) "passive" elements.

It's tricky ... You could look at the system as n receivers connected to n antennas or as n receivers connected to a single n-element array. Probably some other ways I'm not thinking of.

How is control of the array performed: Fully centralized, fully distributed or ??? I suspect a legal judgment will depend heavily on this point.
posted by ZenMasterThis at 7:56 PM on December 10, 2014


Have you tried using an amplified antenna? I tried a small un-amplified one and it wasn't great but this one pulls in every available channel in my area.
posted by Poldo at 9:05 PM on December 10, 2014 [2 favorites]


Sounds like they're using the mini-antennae as a phased array. Nothing bullshitty about that at all; astronomers have been using that cheat for several decades.
posted by IAmBroom at 7:24 AM on December 11, 2014


I'll disagree: if it does operate like a phased array it is bullshitty because this was Aereo's entire business model (and marketing, and public relations, and court battles all the way to their Supreme Court testimony).

This was all based on the idea that an Aereo customer rented and controlled a single ATSC antenna, very similar in function to something you could purchase at Best Buy and install on your roof, only that it was offsite and sitting in a server farm so you could dump shows over the cloud. The miracle breakthrough being the idea that Aereo figured out how to make an individual antenna so small that they could cram 100,000 or 1,000,000 on a roof and serve a whole community.

This is why OP was asking "why can't I just go to Best Buy and buy one of these little antennas if they work so great?" And it's looking like that was never possible. Therefore, bullshit.
posted by JoeZydeco at 7:44 AM on December 11, 2014


It's not quite dime-size, but USB digital TV tuners that are USB dongle-sized are readily available. They're of interest to hackers because they are easy to reprogram and use as a $20 software defined radio, as opposed to the $500+ purpose-built hardware costs. (Keyword: RTL-SDR). Technically speaking these things are not antennas, you still have to plug the antenna itself in. But even without an antenna they can receive pretty well, AM radio for sure.

AFAIK no one sells these devices in boxes on shelves in the US. Most enthusiasts buy them via eBay or weird Amazon Marketplace sellers. I assume they're just unlabelled Chinese goods. Although a quick look on Amazon shows some more US-consumer-friendly options.
posted by Nelson at 8:38 AM on December 11, 2014 [1 favorite]


Tablet TV is going to be selling a DTV tuner device that's small and may fit your needs. It's basically a phone-sized device that has a battery and some memory and transcodes the OTA MPEG2 streams into HLS (h.264 - what most people would call MPEG4 but I guess it's technically an MPEG2 transport stream encoded in h.264, it's a container versus codec distinction) which you can watch on your tablet and probably eventually on other devices as well. It's also an OTA DVR.

The advantage there is not that the antenna has better gain like a big antenna on your roof so much as that you can put the antenna anywhere and there's no path loss or interference inside you house because it's all digital.

Anyway, I'm told it will be for sale nationally in the US next year.
posted by GuyZero at 8:53 AM on December 11, 2014


Is there a way I can set up an array

Not really. Without getting into detail that I'd get wrong (not an EE at all, but an interested observer with a similar directional problem) that's Not How Antennas Work. Whenever you connect multiple antennas together, lots of complicated things happen that mostly make it harder to tune anything at all. There's a two antenna trick that can be done to reduce ghosts, but it requires lots of fiddling to make sure you're not making other problems worse. If you're just trying to tune channels broadcast from multiple directions your best bet is an antenna with a response pattern that matches your need, carefully aimed.
posted by fedward at 4:13 PM on December 11, 2014


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