Author Topic: HDTV Antenna - Helps you cut the cord from cable  (Read 6847 times)

Offline AngusBangus

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HDTV Antenna - Helps you cut the cord from cable
« on: August 01, 2012, 09:22:52 AM »
In an effort to drop our monthly expenses and spend more time together as a family, we are cutting the cord from cable. We're keeping the internet... and I can't completely shed TV. I still want to see a radar, watch football, breaking news, etc. So I decided to build an HD antenna, which allows me to get all of the major networks plus another 15-20 channels (your mileage WILL vary based on your location and topography). This assumes that you have a relatively modern TV. If not, you'll also need a little box that will convert the digital signal to the air. You can pick a quality one up on Amazon for $20-$40 (search "digital converter"). You'll save that the first month you ditch cable.

A little background: Since 2009, broadcasts are provided in digital formats over the air. They are almost all in the UHF frequency range, with a few in the VHF range, and most of those in the nigh VHF (near UHF range). This means that a UHF-only antenna will typically get you what you need. To figure out what you need, go to TV Fool. You can get stations in your area to help select/aim your antenna and see a coverage map to know how much meat you need in your antenna. In my market, there is only 1 station in the VHF range at channel 7, so it is high enough frequency that a UHF antenna will do. Further, I'm on a hill so have line of sight (for RF) out well past the 20-30 miles I need, so my antenna is up in the attic. Depending on your situation, you might be able to just put this right behind your TV. Here's what I built and what you'll need to do the same.


Material:
4 all-metal coat hangers (not with the cardboard bottom for pants)
2 pieces of wire/coat hanger/other conductor about 30" long to connect the elements
10 bolts/nuts (I used 2" #6x32)
10 finish washers (flat washers OK, but finish washers hold down elements better)
1 Mast (I made mine by taping together the 3 legs from an old easel, ANY non-conducting strip of material will do... plexi glass, PVC, even cardboard)
300:75-ohm matching transformer ($6 from Radio Shack, this is the thing that has 2 terminal connectors on one end and a coax connector on the other... think old TV antenna connection).

Tools:
Safety glasses
Wire cutters (that can handle a coat hanger)
2 Pliers (to bend coat hangers)
Ruler/Measuring Tape
Sandpaper (I used 320 grit, any coarse grade will do)
Sharpie marker
Drill
Electrical tape
OPTIONAL: Soldering Iron

Construction:
I. Make elements (Put on your safety glasses for this. Sometimes the coat hanger parts will fly away. You don't want them to end u pin your retina.)
1. Clip hangers at the "neck" to get rid of the hanger part.
2. Straighten each hanger using 2 pairs of pliers (or by hand if you're a machine).
3. Clip the hangers into two 16-inch lengths (you'll have an inch or 2 left over).
4. Sand the coating off the middle of the hanger. This is REAL easy and quick... 5-10 seconds per piece. You'll know when you've succeeded because the hanger will be bright silvery virgin metal.
5. Meaure to the midpoint of the elements and make a small mark.
6. Using the pliers, bend each piece of hanger into a "V" with a relatively tight corner. You should bend the V so that the tips are 5" apart, leaving each elements with 2 8" arms 34-degrees apart. Unless you are a machine, you won't be able to get them all exact. Don't sweat it... make one good one, compare all the other ones to that one.
7. I used some red duct tape I have to make a small tab on the end of each element. These things are sharp and could easily end up inside my skin or my eye. This is an EASY precaution. Use the electric tape here or anything else non-conductive that you'd like.

II. Make base
1. Starting a few inches from the top, mark 4 sets of 2 holes spaced every 8 inches down the length of your board. The distance is about an inch apart but not critical for this application. I used 450-ohm window line (I'm a radio nerd).
2. Also mark 2 holes at same distance apart between the 2nd and 3rd set of holes. You end up with a hole at 0", 8", 12", 16", 24" from your starting hole.
3. Drill the holes out large enough for your bolts to go through.
5. Insert the bolts with the washer on the top side and get the nut started on each one.

III. Assembly & Installation
1. Lay your long connecting wire down so that it will be connected to the top/bottom ends on one side of your board and the middle 2 connections on the opposite side of the board. Your conductors will cross at each end. You can see that in the photo above. If you aren't using an insulated wire to begin with, you should insulate the two from each other where they cross. If you need to do this, wrap one or both wires where they cross with electrical tap. It should be laid out like this:

1    2
   x
2    1
|     |
2    1
   X
1    2

2. Install each element (opening of "V" facing out as shown in picture) under the washer, making sure that it makes good contact with (is "squished" into) the long connecting wire. Tighten it down well.
3. Even our the elements so it looks like you ahve 4 X-wing fighters stackd on top of each other.
4. At the middle bolts, slip each of the terminals of the 300:75-ohm matching transformer thingamabob under one side of your connecting wire and around the bolt. Tighten it down well.
5. If you used bare wire for your connecting wire, cover it up with electric tape where the end of the transformer ends up. You don't want to create a short circuit in your antenna by letting the metal coax touch the connecting wires. That'd really mess up the RF response to this thing.
6. OPTIONAL: I you'd like to really do this thing up, you can solder all of the metal-to-metal connections. As this is a receive-only antenna (no radiated power) that won't see any external stress (wind/rain), this step is beyond overkill. If you think this step is necessary, you are advanced enough that you didn't need this how-to in the first place. :)
7. Connect a length of coax to your TV and to your antenna. Put the antenna as high in your house as you can and away from metal ducting. My cable was already run through my attic. So I just disconnected the TV cable from a splitter and connected the antenna.
8. On the TV, navigate to the Channel area of your menu and the "autoprogram"

The TV will run through a scanning sequence to find all the available channels. Compare the results your TV ends up with to those from your "TV Fool" report (at the link above). If you didn't get everything you expected based on the reports, there are a few things you can do in the DIY world (amplifying it is probably a step too far):
a) Raise the antenna. Height above ground is your friend. The higher you go, the fewer leaves/trees/buildings the signal has to get through between the transmitter and you.
b) Build 2 versions of this antenna and connect them together. If you want/need to do this, here's a schematic. Note: Balun is another term for matching transformer. This also has a reflector to further boost/directionaliz your signal:


My boys fell asleep during construction, so they will be helping me when I upgrade mine to a two-bay antenna and hang that one with some 550lb paracord at the peak of my attic. I want to get everything I can an potentially use it with my handheld HAM radio too. So I'm looking for a little more gain.

Offline backwoods_engineer

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #1 on: September 08, 2012, 12:19:59 PM »
Good work.  Thanks for posting.  May come in handy.

For the uninitiated, a home-built antenna like this will work just as well as something you pay over $100 at Radio Shack for.  I've been building my own antennas for over 35 years.

Offline AngusBangus

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #2 on: September 10, 2012, 06:59:22 AM »
Good work.  Thanks for posting.  May come in handy.

For the uninitiated, a home-built antenna like this will work just as well as something you pay over $100 at Radio Shack for.  I've been building my own antennas for over 35 years.

Yeah, that's the HUGE secret in the antenna industry. A guy with some cheap hardware store materials can build something that works just as good or better for a fraction of the cost.

For example, due to the overkill method I use in selecting materials and doing my soldered joints (because I'm not a highly trained robot welder), antennas I make will be more robust than a store-bought design. Now, the things you buy are superior in some situations - like a vehicle-mounted antenna. But even those can be topped more cheaply if you have the mechanical skill and purchase a few of the specialized parts.

Bottom line, if you have a need to receive or even transmit RF, download a book or two, read about the simple calculations, and go to Home Depot. You will save yourself literally hundreds of dollars with only a few antennas.

Offline mike77

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #3 on: September 10, 2012, 07:38:03 AM »
I know about antenna building from ham radio, but never thought of doing so for HDTV. Thanks for pointing it out!
Is your design directional? I haven't seen one like it before in the ham world.

Offline fritz_monroe

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #4 on: September 10, 2012, 08:07:22 AM »
Thanks for sharing.  I've been meaning to cut the cable, but my wife has several shows that require broadcast TV.  And as we all know, Happy Wife, Happy Life.  So maybe I'll give building my own antenna a shot to see what I get.

Offline ttubravesrock

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #5 on: September 10, 2012, 11:20:14 AM »
I've been cable-free for years.  I meet my needs by paying $8/month for netflix and sacrificing the ability to watch football at my own house. 

Offline oktheniknow

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #6 on: September 10, 2012, 11:42:27 AM »
Good one. We bought an HD antenna online awhile back for $15-$20. It picked up all but one local channel. Need to run it up through our attic to see if it improves the reception to get the other channel. Used to listen to shortwave radio and had an outdoor antenna that ran the length of the back of the house.

Offline backwoods_engineer

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #7 on: September 10, 2012, 12:27:14 PM »
I know about antenna building from ham radio, but never thought of doing so for HDTV. Thanks for pointing it out!
Is your design directional? I haven't seen one like it before in the ham world.

Yes, it's directional.  The metal/foil screen is the reflector, so point the element side toward the TV tower :-)

Offline fritz_monroe

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #8 on: September 10, 2012, 06:57:26 PM »
Okay, here's a couple of questions. 

I don't see that you give a mast length.  Since the conductor length is 30", it looks like the mast is about 36" or so, but pictures can be deceiving.

Is there any reason that scrap copper wire can't be used for this?  I have some scrap that I could use, but I guess exposed copper would corrode pretty well.  Maybe spray all copper after assembly with a lacquer to keep it from corroding?  And I know that coat hangers are virtually free, but so is this scrap copper.

Offline mike77

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #9 on: September 10, 2012, 10:40:51 PM »
Yes, it's directional.  The metal/foil screen is the reflector, so point the element side toward the TV tower :-)

How directional is it? From my house the transmitter towers for most stations are in about a 40 degree arc.

Offline Meldrew

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #10 on: September 11, 2012, 12:03:03 AM »
If you have an old TV antenna laying around that will work well too.  There's nothing "digital" about the signal per se.  The signals themselves are still VHF/UHF just as before though what you get is now digital not analog. 

I have my dad's old antenna stuck up in the attic and am receiving signals as far as 50 miles from the house. 

I DO wish I had the rotor too. 

Offline Outdoorfury

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #11 on: September 11, 2012, 10:01:56 AM »
we cut cable over a year ago and we are saving money and spending more quality time together as a family. I feel that cable sucks out your brain and thing blends it with stupid... not that primetime shows like the bachelor are not just as bad but their is less temptation with a few channels.

Offline AngusBangus

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #12 on: September 12, 2012, 10:16:49 AM »
I don't see that you give a mast length.  Since the conductor length is 30", it looks like the mast is about 36" or so, but pictures can be deceiving.
About 30" is right. Each element is actually a "V" shape with 8" arms. The angle I bent them to leaves 5" between the end of each arm and the elements were spaced at 8" on center. So the minimum mast length would be 24" (3 gaps between the 4 elements on each side) plus a little on each end for making the mechanical connection. The spacing between elements and angle you bend them to should just affect your bandwidth/lobe shapes. This is a pretty forgiving design though.
 
Is there any reason that scrap copper wire can't be used for this?  I have some scrap that I could use, but I guess exposed copper would corrode pretty well.  Maybe spray all copper after assembly with a lacquer to keep it from corroding?  And I know that coat hangers are virtually free, but so is this scrap copper.
Absolutely you can use scrap copper. I would note however that changing the diameter of the element (thin wire vs thick coat hanger) will change the bandwidth of the antenna. Typically a thicker element will provide higher bandwidth. I really was giving the design using items that most folks have sitting around their house. I, for one, am ALWAYS looking for something to do with the hundreds of wasted coat hangers in my wife's closet (only because that's where the space is to hang them). I used to save the hangers I would bend into marshmallow roasters... but then I realized my supply is basically endless, so I started throwing them away rather than clean them. As far as spraying the finished product with a protective coating, it probably isn't worth the trip unless you're going to hang/mount this antenna outside.

Offline AngusBangus

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #13 on: September 12, 2012, 10:49:14 AM »
How directional is it? From my house the transmitter towers for most stations are in about a 40 degree arc.

As shown, this design doesn't have to have the reflector. Adding it is a huge complication compared to just bolting on the elements.

With the reflector, it is strongly forward biased (meaning in the direction coming out of the screen at you). Without it, it is still biased in the forward-read direction. There is not much gain - and actually a pretty solid null - off the ends (to the sides) of the antenna. The way I originally hung mine (from some 550 cord in the attic, it had a tendency to twist on me. When that would happen, I would notice little glitches in my signal as the antenna had rotated almost 90 degrees. So it will still pick up the signals from 20-30 miles away, but there are many more "signal fades" which appear as pixelation/pauses/drops. I would think a 40-degree arc should be fine. I would also guess (rectal pluck style) that if you have that wide an arc that you are probably relatively close and should be getting pounded by the signals and it won't matter. If I were you, I would build it without the reflector and put it up there aiming in the middle of the 40-degree arc. Then the station furthest off-axis is only 20 degrees off.

If my assumptions are wrong and you have both a 40-degree arc of stations AND they are relatively far away, perhaps you could build the dual array (16 elements) as shown in the red-blue picture. Don't add the reflector, but twist each set of elements out from center so the array would appear convex to the center of your 40-degree arc (imagine putting your hands up to catch a ball from both short stop and 2nd base simultaneously). If you imagine the forward/rear bias of each set of elements as a flashlight, you can work with that visualization to get what you need.

Offline MattR

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #14 on: September 28, 2012, 10:57:46 PM »
At our previous house, I made a similar design and used 1x2 aluminum tubing instead of wood, aluminum welding rod for the arms and neoprene washers so they didn't touch.  Attached it to a 3' aluminum pole and then to my house.  I also have a regular antenna that is on the roof of our new place and I use it as a backup when satellite goes out due to a really bad storm.  I can still get local HD channels even though I am about 65 miles from the city.  Nothing like a backup plan.


Offline fritz_monroe

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #15 on: August 03, 2018, 05:55:13 PM »
Well, I didn't really cut the cord.  The wife was having none of that.

I decided to go with a streaming service.  I signed up for YouTube TV.  It covers every channel we (i.e. my wife) needed except Hallmark.  This took my bill from $103.28 to $40.  Of course since I haven't been billed yet, I don't know if there will be any additional charges.

Hallmark was easy to get over.  I told the wife that we could keep the satellite service, but that she would need to write me a check for $60 each month to cover the difference.  I took a gamble and it paid off.  hehe

Offline Carl

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #16 on: August 03, 2018, 06:48:40 PM »
  Those who can get,or still have,an old TV antenna about might be surprised to discover that it will do a great job on digital TV though most areas need only the UHF (smaller set of elements) to cover all area stations .

Offline Redman

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #17 on: August 04, 2018, 05:23:39 AM »
We have an older analog TV and are line of sight at approx. 25 miles from the antenna farm in Stafford, TX. We opted for Netflix and Hulu and bought this antenna for $9.95 and a converter box. Set both on top of the TV. Works quite well.


Offline Carl

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #18 on: August 04, 2018, 06:15:22 AM »
  You really get range with the accessory aluminum foil :D

Offline fritz_monroe

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Re: HDTV Antenna - Helps you cut the cord from cable
« Reply #19 on: August 04, 2018, 09:10:24 AM »
I tried an antenna and an HD Homerun to do the DVR thing.  I tried it on the ground and got a couple of channels, and am pretty sure I'd have gotten many more on the roof.  However, the wife has a couple of channels that are a must, they aren't OTA channels.