
How I made an HDTV antenna so I could watch Jeopardy last night - chaosmachine
http://blamcast.net/articles/how-to-make-an-hdtv-antenna
======
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...](http://www.instructables.com/image/FDXQQVBFP8NM7YF/Create-fractals.jpg)

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

~~~
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.

~~~
Groxx
I watched a Nova on fractals not too long ago, it covered this bit exactly.
Definitely a cool story :) I don't 100% remember the title, but I think this
was it: [http://www.pbs.org/wgbh/nova/physics/hunting-hidden-
dimensio...](http://www.pbs.org/wgbh/nova/physics/hunting-hidden-
dimension.html)

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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.

~~~
CWuestefeld
_I went to fiddle with the cable and noticed it was not even plugged in._

Back in college, we were watching a, umm, adult video on my roommate's VCR.
The guy from the room next door walked past, and said "oh, you're watching the
movie too?". It turns out that we'd mistakenly connected the VCR's RF _output_
to the antenna, so the guy next door was watching our transmitted movie.
(although his picture was poor)

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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.

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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!

~~~
chaosmachine
South end of Ottawa :)

~~~
jbrennan
Well that settles it. I'm buying a spool tonight. Thanks!

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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.

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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?

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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

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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>

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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...](http://www.re-nest.com/re-nest/how-
to/how-to-make-a-string-tree-wall-mural-home-hacks-109655) Thanks!

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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>

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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.

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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/...](http://www.amazon.com/RCA-ANT1650-Digital-Amplified-
Antenna/dp/B0027FGW3K)

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.

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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.

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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...](http://www.82smugglers.com/gallery/projects/p1020110.jpg.html)

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

~~~
minalecs
same here... I receive over 30+ channels now, most are HD (LA) area. With this
and a computer hooked up to my TV would never consider going back to cable.

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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.

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

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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.

~~~
barrkel
Enjoy the pyrotechnics during the next thunderstorm.

~~~
ja27
Also, static electricity will build up on a wire like that unless you bleed
the charge off to ground with something like a nice high-ohm resistor.

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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.

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

~~~
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.

~~~
bryanlarsen
Nah, it's to ground the shield. Shields work marginally better when grounded,
but the difference is minor.

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rms
Private Justin.tv broadcast anyone?

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xutopia
What size is the cardboard tube?

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idknow
whoa; that's too kool; congratulations!!!

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daniel_levine
can we see how it was put in the window?

~~~
chaosmachine
Sure: <http://i.imgur.com/jOiWI.jpg>

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delinquentme
lol whut. THATS TOO EASY!

