How I made an HDTV antenna so I could watch Jeopardy last night

[dpapathanasiou]

You'll get even better reception if you shape the wire in a fractal pattern, like this: http://www.instructables.com/image/FDXQQVBFP8NM7YF/Create-fr...

Nathan Cohen made this discovery after listening to a Mandelbrot talk on fractals: http://en.wikipedia.org/wiki/Fractal_antenna#Fractal_element...

[jobrahms]

"Nathan Cohen made this discovery..."

He's the reason you don't have a stubby antenna sticking out of your cell phone anymore. Really cool story.

[philsalesses]

I can't be the only person to notice that not every angle on the instructables example can be 60 degrees.

[Swizec]

Thanks, I'm glad you took our comments to heart :)

Two questions:

1. What exactly is the purpose of the cardboard tube? I'm guessing the key point is that it's non-conductive, but would the same coil work without the cardboard? (not very knowledgable about antennae I admit)

2. How the hell does that connector even work? It looks so marvelously out of place ... does this mean the wire mesh around the normal coaxial cables is just shielding and doesn't actually do anything? If so, how come you don't need shielding?

Those were the two main questions that popped to mind, obviously I don't know anything about this stuff and I could probably look it up somewhere. But maybe someone here can provide a human-to-human good enough explanation.

[Retric]

Shielding is useful but not exactly required if the signal is strong enough and the cable is short enough. EX: You can use barbed wire to send 10 baseT. However, 1 gigabit has major issues without shielding.

PS: I once noticed my Sega genesis was producing a vary fuzzy picture, so I went to fiddle with the cable and noticed it was not even plugged in. At the time I really freaked out and to this day I still wish I had a picture.

[ja27]

The shell of coax (and what's in the space between it and the center conductor) also affects the impedance of the cable or antenna system. It's generally not that critical for a receiving antenna.

Sticking up almost any wire more than a few wavelengths long will collect a reasonable amount of a strong signal. A truly resonant antenna for the frequency you're interested is a lot better, but not that helpful for general HDTV viewing where the frequencies range all over VHF and UHF.

One of the amazing things I've learned from years of ham radio is how many unseen and unpredictable things affect radio signals. You can move your antenna twelve inches to the left and lose a signal completely, especially inside a structure. Or an airplane flying overhead can reflect enough "multipath" signal to wreck your TV viewing for 30 seconds. Of course your own body blocks a lot of signal and is capacitively coupled to the antenna system as you adjust it. So if you're playing with an HDTV antenna and are too young to remember the fun of constantly adjusting TV rabbit ears, just keep tweaking until you get a good signal.

[chaosmachine]

1. Basically, I just wanted something I could wind a length of wire around and stick in my window. The tube did the trick. After the show, I tried a few other things, like wrapping the tube with tinfoil, but the basic wire around the tube design performed best.

2. The shielding is there to keep signal interference out, which is useful if you have a clean source to start with (ie: Cable TV or a properly designed antenna). In my case, I just wanted to pick up as much signal as possible, and this is what I had to work with.

[Pyrodogg]

1. Structure. The wire he's using isn't strong enough to just stay up standing by itself. It would fold over on itself. Also, it probably does need to be non conductive or you need to use coated wire.

2. It's not shielded because the entire thing is the antenna. I guess he could shield it between the TV and the actual wrapped tube part but this is sow low-tech it wouldn't make a difference. Your standard roof mounted antenna is shielded between the antenna and the tv because you don't want interference between the two points.

[arandomJohn]

My HDTV antenna is a paperclip stuck into the back of a TiVo. I get solid HD reception, no artifacts or other problems. It is all about how close you are to the broadcast towers. I have line of sight to towers that are about 12 miles away.

[jbrennan]

Which city are you in? I'm in downtown Ottawa and with a store-bought HDTV antenna I get only 2 stations. Maybe I'll have to go buy a spool of wire!

[adestefan]

Go to tvfool.com and put in your addresses. From what I can find they have Canada data in their DB too. The first step to understand how to get good reception is to learn where all the towers are located and what band they broadcast on.

[chaosmachine]

South end of Ottawa :)

[MikeCapone]

I had the same experience in Vanier (Ottawa East..). I actually brought back the antenna to the store because I thought it was broken.

[thought_alarm]

You can use http://www.tvfool.com/ to chart the strength of nearby TV signals based on your location. It includes both US and Canadian broadcast towers.

I'd be interested to know the strength of the signals you're able to receive with your paper-towel-tube antenna design.

[ck2]

If you are smack in a city where the signals are literally washing over you I guess just a wire will work.

The coathanger antenna works best for me though, I'm too far away from most stations for just a wire.

Your design might work best for VHF stations while the coathanger method is best for UHF

Canada still has analog stations?

[emehrkay]

Just made one of these, really really half-assed.

I had to strip a coaxe cable with a pair of scissors and my hands. That took at least 20 mins.

But here we are

http://imgur.com/a/6mE0W

I have to remember to take that down before someone gets cut in half running down the stairs

[alanfalcon]

If you're more lazy and don't mind watching someone watch the show, this worked at 7 PM Eastern yesterday: http://www.ustream.tv/channel/final-jeopardy-man-vs-machine

[ortusdux]

Ive been looking for an excuse to do this: http://www.re-nest.com/re-nest/how-to/how-to-make-a-string-t... Thanks!

[akeck]

Gray Hoverman antennae do a good job for longer distances: http://www.digitalhome.ca/ota/superantenna/

If you search a little more through the http://www.digitalhome.ca/ forums, you can find newer generations of the design. Various folks have been using genetic algorithms to find more efficient modifications to the original design. http://www.digitalhome.ca/forum/showthread.php?t=119489

[BrandonM]

My antenna is currently a coaxial cable screwed into the back of my TV and extended up to my curtain rod. It looks like I'm getting curtain-rod cable.

[aantix]

I have an antenna from RCA that is "enhanced". When I plug it in, it definitely helps in solidifying the picture.

http://www.amazon.com/RCA-ANT1650-Digital-Amplified-Antenna/...

Using your antenna, how could I go about amplifying the reach in an attempt to pick up more channels and/or increase the display quality of current channels?

[kd0amg]

Going through common antenna design compromises...

Depends on your location, of course, but the most effective thing I could do is get out of this valley. Next, I'd straighten the antenna wire and move the antenna outdoors (with a 75Ω coax line connecting it to the TV). You could also adjust the length so it's resonant at a particular frequency, but that will weaken the signal you receive on other channels. Alternatively, cutting it way longer than the minimum resonant length (like an order of magnitude or so) seems to make for a pretty forgiving frequency response. Then again, commercial broadcast transmitters are probably running enough output power that unobstructed line of sight makes more of a difference than anything else can.

[jim_lawless]

I've gotten pretty good reception with a UHF loop antenna like catalog # 46-200 pictured here:

http://www.farnsworthelectronics.com/antenna.htm

I use a matching-transformer to connect it to the coax plug.

[minalecs]

Heres plans for an antenna I built. http://www.tvantennaplans.com/

I like the simplicity and potential of your design though. I want to try an array of tubes and wiring, and see how well that works.

[timmaah]

I got the same plans via Make and have been using mine for 2+ years. It works awesome. Before dtv I could get 1-2 stations of mostly fuzz. Now I get 7 channels in full HD.

http://www.82smugglers.com/gallery/projects/p1020110.jpg.htm...

Tried some shielding on the back and it did not make any difference.

[ck2]

Note that 4-bay may be overkill depending on how far out you are.

I can get all the stations possible in my area with just 2-bay.

So build with 2-bay first and test maybe to save time/money.

I also did not need the reflector, in fact it made things worse.

[AdamTReineke]

I was looking at that design yesterday. I decided I didn't have the time to buy the materials and build it in the 30 minutes I had before the game started, so I ended up watching on Youtube. I plan on building this antenna in the future though.

[graywh]

Google Chrome is warning me that soccergoalplans.com is including content from an external website known for malware.

[cappaert]

Does this work in the US? I've been under the assumption that with the recent switch from analog to digital signal (and the need for a digital converter box), connecting an antenna straight to a TV no longer works.

Thoughts?

[sp332]

The frequencies are the same, and since they're not doing anything freaky with the signal (just broadcast) the same kind of antenna ought to work. In fact, you should get a better signal, because ATSC has much better multipath resistance than NTSC did.

[elxrr]

Mine is just a copper wire, no fancy cardboard tubes or coils.

[PaulHoule]

I'm in a place that's hilly and the towers are far away. Maybe I'd get something with a 75 foot tower, maybe.

For me it's ivi.tv

[JonnieCache]

>Maybe I'd get something with a 75 foot tower

    1) Attach 75-foot wire to TV
    2) Attach other end to weather balloon
    3) Inflate balloon
    4) Watch Jeopardy

Maybe tie some brightly coloured threads onto the wire at intervals to stop birds flying into it.

Note: there are probably many other reasons why you shouldn't do this. Make sure to let us know when you find out what they are.

[narodick]

This article is excellent! And thank you, chaosmachine, for providing instructions for replication.

It's my strong opinion that everything here is ethically sound. This sort of "hacker" culture is the meat and potatoes of what drives innovation in the United States today, and whether this specific incident results in a new product or simply higher security by cable providers, progress has been made.

[daxelrod]

What do cable providers have anything to do with this?

He built his own antenna to receive local channels that are broadcast over the air. These are broadcast specifically so that people with antennas can receive them.

[tocomment]

Why doesn't the outside part of the coax port have to also touch the wire?

[gcheong]

Because no signal is transmitted on the outside part, that is just used to secure the cable to the port. If you look at a coax cable, you will see it is essentially a copper wire wrapped in shielding wrapped in a vinyl(?) casing and the end is terminated with a connector that feeds the copper into the port and secures the connection.

[icegreentea]

I don't think coaxs have a 'return' on the actual cable. The outside part of a coax is just a screw for holding the cable in place. It could be made with plastic for all it matters.

[rms]

Private Justin.tv broadcast anyone?