Good Digital antenna cheap!

In the USA we have all heard that analog TV signals will disappear on February 17, 2009. Everyone receiving a signal through the air on an older television will need a converter box for Digital TV.

We bought a box, but it was a while later that we learned we needed a special antenna to go with it. We bought the one shown in the photo. It also comes with an active (powered by a voltage adapter) signal amplifier. This one is $37 at Amazon.com (plus shipping and handling). I must be slow mentally, because it took me a while to realize the Digital TV signal utilizes a basic UHF antenna.

We live 30 miles (48 km) from the local broadcast towers. An antenna like this should give us super fine reception. But, pointing it in the exact direction of the tower is critical. It does not function well without the signal amplifier, and the picture pixelates or goes to "No Signal" when someone walks across the signal path in another room. Mounting it in the attic might help, but one of our stations is located about 45 degrees clockwise from most of our stations.

For pennies I made a better antenna.

Step 1: Start making the antenna

Cut two strips of thin sheet aluminum 1 1/8 inch (3 cm) by 6 3/4 inches (17 cm). I considered cutting the aluminum from old soft drink cans. To get the needed length I would have needed to cut down the side and across the bottom. Do that if you have no other sheet aluminum.

Comments

[rowerwet]

what do you mean by 300 ohm wire, that the resistance of the wire is 300 ohms? or is it a wire rating of some kind?

[Phil B]

Cables for connecting an antenna or other signal device (DVD player, etc.) to a television have an impedance given in ohms.  Impedance is a form of resistance to the flow of current and is different from simple resistance in that it involves circuits in which coils of wire (inductances) or capacitors interact with currents at various frequencies.  As the frequency of the current changes in these circuits, so does the resistance to its flow.  A coil of wire may present only a couple of ohms of resistance to a straight DC current, but apply a current at radio frequency and that coil presents several hundred ohms of resistance to the high-frequency current.  That is why small coils of wire in a radio circuit are called a choke.  300 ohm twin lead is flat TV signal cable that presents 300 ohms of resistance at television signal frequencies.  See this article.  Coaxial cables more frequently used now for digital signals have an impedance of 75 ohms.  A small transformer can convert the signal from 300 ohms to 75 ohms.

[static]

300 oms means that twin lead has a characteristic impedance of 300 ohms. Most UHF TV antennas use a folded dipole as the driven element, a folded dipole has a characteristic impedance of 300 ohms that's why twin lead has been used over the years, so there's no impedance mismatched. LOL just dawned on me you are feeding a plain dipole that has a characteristic impedance of 75 ohms with the twin lead. No matter rabbit ears use twin lead, and all works sometimes. that why the term is "characteristic impedance.

[rowerwet]

thanks, I never knew that and I wire stuff at work all the time, mostly DC though so low ohms readings.

[Phil B]

I do not work with these things, but have read bits and pieces about impedance, also known as reactance.  In a radio tuning circuit there is an inductance (coil of wire) and a capacitor.  One of those is variable by means of a tuning knob.  The resistance provided by the inductance reduces or blocks signals.  The same is true for the reactance or resistance provided by the capacitor.  But, at the selected or desired frequency of the station you want to hear, the reactance from the capacitor has the effect of countering the reactance or inductance from the coil of wire.  The result is the frequency you want is allowed to pass relatively freely. 

I am glad to have been of help.

[Vinsu]

Don't know if relevant but in Finland these "converter boxes" are called "digi-boxes". Came by when analog transmissions ended here in 2007.
Just thought to let you know.

Digi-digi ^^
Over and out.

[-=Dr.Who=-]

Try perforated aluminum or perforated stainless steel. Either one will work great and no worries about structural strength. Even heavy mesh metal screen (like a good strainer) can be used with just a little bit of aluminum or steel rod for support.

[-=Dr.Who=-]

Hey Phil B,
Great 'ible! You did a really nice job of it.

But something caught my eye when you said that you "needed a special antenna" to go with your new converter. Truth is, no you didn't! Your old antenna would have worked just fine with your new converter. I wish I could have gotten the word out to more people sooner about this misconception. I want to dispel that rumor about the need to buy a new "Digital Antenna" due to the format changes in broadcast TV.

There is no such thing as a Digital Antenna. All radio-waves are analogue (sinusoidal) by nature. The information carried within those radio-waves can be either analogue or digital. The data carried within a transmission has no bearing on the radio-wave that carries it. Hence, there is no such thing as a "Digital Antenna".
I feel that it's important for people to know the truth in things. This is one of those things. The amount of dis-information out there on this topic is staggering to say the least. So, I've tried to boil it all down. (Note: I said Tried to boil it down)

Note to Everyone:

There is NO REASON to buy a new antenna due to the Digital Format changeover! The frequencies for your broadcast stations HAVE NOT CHANGED! Your 40 year old rooftop antenna will work just fine for you as it has in the past. The only thing that changed is the SIGNAL FORMAT.

The Stations you watch are still using the same transmitters they were before the changeover. If all the broadcast stations were forced to change out their main transmitting amplifiers, there would have been a HUGE uproar from the station owners\operators in the Broadcast community. The F.C.C. would have had billions of dollars worth of lawsuits on their hands if that had been the case. Not to mention the infrastructure changes! It would be easier to overhaul the entire Internet than it would be to change TV broadcast frequencies!

In simple terms it goes like this: Analogue TV is like a dial-up modem connection to the Internet.
Whereas
Digital TV is like a High-Speed Cable connection to the Internet.

The difference is this: Capacity!

By changing the Broadcast Format to an all-digital format, the same Broadcast Frequencies can be used more efficiently thereby allowing more broadcast stations to utilize the limited frequency range that is currently allocated for Television Broadcast Transmissions.

Currently there are only a few truly "New" channels (at least in my area) that have been added since the changeover to the new format. But, as with anything that has been changed, the Broadcasters are still learning about what they can do with this newly found space in the air-waves. Some stations have second and a third sub-channels they have added to their broadcast line-up. In my area, channels 10 and 13 both have a sub-channel, 10.1 and 13.1. And channel 6 has 2 sub-channels.

In a couple more years, even more new stations will pop up and soon we'll be right back where this all began... when someone decided they wanted to start their own TV station, but the F.C.C. had to tell them NO, because there just weren't any channels available. While this is technically true, there are a lot of empty channels that don't seem to be in use by anyone, so how can this be the case?

Simple: Someone else currently holds the broadcast license for that channel.

So began a series of events that ended in this changeover to DTV. A restructuring and reorganization of the space available within the broadcast frequency range. Now, instead of some 60 or 70 channels carried within the frequency range, there are potentially thousands of channels (or more) now available within that same frequency range!

So, if the frequency range that TV is transmitted in hasn't changed, why should your antenna?

In short, it doesn't need to change. It's still receiving the same signals as it was. The only thing that changed was the way information was formatted within those signals and how those signals are decoded by your TV's tuner. However, given all that has been said, there is nothing stopping you from designing and building a better antenna! In fact, the antennas that you can buy at places like Wal-Mart, Target and anyplace that sells TVs, leave A LOT to be desired. These antennas will almost certainly be of the Set-Top variety. If you have a good antenna on your roof already, DON"T WASTE YOUR MONEY!!! they're just trying to "Up-Sell" you on junk you really don't need.

I mean, who wants a pair of "Rabbit Ears" poking out over the top of their brand new Flat Screen? I have mine sitting on top of the entertainment center where it's less noticeable. LOL!

Personally, I think the change that was forced upon all of us was unconstitutional. It caused a lot of people to fork out extra money for these converter boxes or buy new TVs in order to be able to watch TV at all. No one had any choice in the matter. Our government made the decision and we, the consumers, paid the price. At this point I don't know what, if anything, there is we could about it now. But that's just my opinion on this subject.

The Fact is, you don't have to buy a new antenna but, better antenna designs are out there if you look around. Radio Shack still sells a few really good roof-top antennas as well. If you decide to build your own, you can get really creative with your designs too. Anything from Retro to Techno is possible. It's up to you, the builder.

Phil B has done a great job with this 'ible. I'm not at all surprised that Phil B got better performance from his creation than he did from the store-bought unit. If you're really into building antennas (as I am. Old HAM operator here) then you might want to go check out www.arrl.org/shop/Antennas/ Great job on both counts, Phil B! Keep up the good work!!!

[adambh]

An old satellite dish should work. There's one on my roof from when I moved in that I don't use. If I pointed it in the direction of the towers and mounted this aerial where the LNB goes, it may be ideal. 

[Phil B]

Yes, that should work pretty well.  A dish focusses to a point where the LNB is mounted.  In theory this little antenna is more suited for a parabolic trough as shown in step 6, but I think what you described would work.

[mackenpoy25]

g

[Phil B]

I do not text, so I am not quite sure what "g" means to you.  But, thanks.

[Dr. dB]

Love the simplicity of this! Who needs a $300 "digital-ready", amplified ultra-mega-stick?

Properly "skinned and dressed", the "pelt" of a standard pop can is about 4" x 8 1/4", so you can readily make at least two 1 1/8" x 6 3/4" strips from one can. (To get a strip over 8", try a spiral cut - probably oughta carve a paper template first, then tape it around a "raw" can and trace with a Sharpie, to get the edges to line up nicely.)

For even more fun, you could select the can(s) and arrange the cut(s) so as to showcase the logo of your favourite product!

Hey! What if you just mounted two whole, uncut cans to the furring strip?!? That would be so classically "ET-phone-home"! Or would the 4 3/4" cans be too short for DTV wavelengths? Maybe "tall-boys"?

Aluminum venetian blind strips may also make for easy antenna elements - pre-curved, so if you glued, screwed or stapled two strips back-to-back, it wouldn't need the furring strip, just a good central mounting/connection block....

[Phil B]

I have to believe your soda can version would work, as would your Venetian blind version (as long as the blinds are not actually plastic).  Give it a try and let us know.  Thanks for your comment.

[subra010]

I cobbled this together after my old antenna stopped working. This works really well and we get all the UHF stations in our area (Minneapolis). Thanks a lot. I cut the aluminium strips out of an old discarded gutter. The strips have some ridges on them but it doesn't seem to make a difference.

[Phil B]

Thank you for trying this. I am glad it worked for you. Thank you for your comment.

[static]

But not all digital TV will be on UHF, in some markets it will be on the VHF channels the associated analog signal has used for years. Here the CBS affiliate will remain on 7 NBC affiliate will remain on 2, PBS on 9. I understand PBS will have a HDTV broadcast, but I don't expect HDTV from the commercial networks in this rural market. www.antennaweb.org should help you find out if you will need both an UHF and a VHF antenna.

[Phil B]

Just recently I heard that TV broadcast repeater systems in the mountains of Central Idaho (relatively little population, no cities) will broadcast digital TV on VHF frequencies. I am not surprised other places, like your area of Kansas will do the same. In that case, your old VHF antenna will serve you well. These aluminum tabs do a good job with UHF frequencies, and if the signals are weak, the parabolic reflector behind the aluminum tabs makes a super passive amplifier.

[Kasm279]

I live in Idaho! im in the valley, though

[static]

With luck you'll be in range of a repeater, that Phil spoke of. Kansas isn't all flat. A nearby small town in a hole, had better and more TV than we living on the flat. The had a tall tower with good receiving antennas that repeated the signals into the hole. I was never aware if they where passive or active repeaters.

[Phil B]

Thanks for the comment. You are over on the eastern end of the state.

[Kasm279]

How'd you know?

[Phil B]

I think your profile says you are from Ririe, Idaho. I checked Google Maps for its location.

[static]

LOL. A good example as to why to provide limited personal information in profile sections. In creating or discussing an instructable or anything that matter, you can end up revealing to the extent of your possessions, to those who would seek to relieve you of them. Mild paranoia perhaps, but who can predict what could take place. In cases where on can't avoid using their ham call sign, enough info is provide so one get get driving instructions to the ham's home.

[Phil B]

If you want to learn a boatload about what I own, anyone with my full name can do a Google search and you get a bunch of hits on things I have reviewed at Amazon. None of them are very rare or fabulously expensive, though. Still, you would learn a lot about my interests.

[static]

With luck you'll be in range of a repeater, that Phil spoke of. Kansas isn't all flat. A nearby small town in a hole, had better and more TV than we living on the flat. The had a tall tower with good receiving antennas that repeated the signals into the hole. I was never aware if they where passive or active repeaters.

[static]

I suppose the rural population density, is to low for broadcasters to be interested. Except for the smallest of villages most towns have CATV. I have been toying with the idea of putting up a passive or flea powered UHF repeater, to improve my reception of UHF translator stations. I have to be careful not to mess up the local CATV reception of the translators.

[Kasm279]

We have satalite TV also, but we cant get 10.2, 10.3, 8.2 etc....

[Kasm279]

EDIT: through the satalite: we still have to use the convertor. we get 10.1, 6.1, and 8.1

[Mr. Squishy]

It said on the DTV website that you will not need a digital antenna. You can use your old antenna. But this is good for people that want better quality.

[Phil B]

The old antenna will likely work if it has a UHF section. We just added another converter box for another TV. It was connected to our old high gain VHF-UHF antenna located in the attic. That antenna is not adjustable as it is installed. It works pretty well if the weather is just right. But, if a front is coming some of the stations pixelate. Some of our broadcast towers are also in a much different location. We switched over to one of the homemade antennae described in this Instructable. It rests on the floor next to the TV cabinet. When a station begins to pixelate, we can change the direction it points just a little and reception is good again. We cannot do that with our old antenna. Earlier today I saw an advertisement for a local firm that will install a digital antenna on your roof for $172.50 and there is no extra charge for the antenna! A homemade antenna can be an advantage.

[dqrwagoner]

I made one using the measurements described out of aluminum foil glued to cardboard and it works great. I also took a piece of 12x18 inch cardboard, covered it with aluminum foil, bent it into a rough parabola and mounted it behind the cardboard antenna using a coat hanger. That more then tripled the signal strength of just the cardboard antenna and took all of 20 minutes. Looks kind of funny but works great!

[Phil B]

Thank you for describing your adaptation. One of the great things about Instructables is that users can adapt what someone has posted so it better fits their needs or the materials they have available. I did something like that with my Instructable on a "Pretty Good Postal Scale from Old CDs." To anyone who jokes about the way your antenna looks I would say, "Do you want to receive a good signal or pay big money to look good?" Thanks again. Your comment has brightened my day.

[multiplecats]

Great Instructable and just in the nick of time. I'm going to try this later after I dig up my old TV wires and stuff. Wanted to also say that you can actually get the needed 3cm x 17cm from an old soft drink can. Simply cut diagonally across the body of the can; one can will yield enough for both strips (you might need to cut the can's bottom off first, to get a good cutting angle). Although, one edge of the strip might be slightly beveled, and I'm not sure this would do to signal reception.

[Phil B]

Thanks for the tip on cutting cans on the diagonal. A slight wedge shape on one edge of the strips probably will have no discernible effect. When it comes to the dimensions I gave, the truth is I just eye-balled what I thought looked good from what worked when I made up a couple of these for UHF channels back some years. I think you will be OK. And, you will not spend a bunch of money on an antenna, like we did.

[Phil B]

Last night we had a little front come through. One channel in particular becomes difficult to receive when that happens whether by analog or digital. I had to change the orientation of the little antenna described here and we got the station, although it did want to pixelate now and then, especially if someone walked near the signal path. This morning I moved the antenna back to its previous position and we are getting all channels just fine without moving the antenna. Also, back in the 1970s I made an antenna like this with a parabolic reflector. Suddenly we were getting UHF channels from more than 50 miles away.

[Kozz]

While I can't speak to whether or not this antenna will do what you need (I don't have the technical chops for understanding antennas), I do feel the need to point out that HDTV is NOT the same as DTV. DTV broadcasts will be capable of transmitting HDTV content, but that doesn't mean your television will show a better picture. You'll need an HDTV-capable display for that.

[Phil B]

Kozz, Good point. I should have said Digital TV, not HDTV. That is my mistake. Still, the antenna described does a better job with the converter box than the commercial unit we bought. Thanks.