The new digital TVs are not like the old analog TVs in that the frequencies in the old analog TVs were hard wired into the tuners. Also, along with many other things, each channel on the TV worked at a particular frequency.
What I mean by this is that channel 2 was a specific frequency lower than channel 8 which was a specific higher frequency as channel 69 was a specific ultra high frequency.
Digital TVs do not work that way. Channel 2 can be any frequency as with all the other channels. The frequencies of each channel is determined by the broadcasters and the agencies that run the broadcasting industries.
For a better understanding of this please go here: Understanding DTV Channel Numbers
Antennas are really only wires connected to a post to hold them in place. These wires are called elements. The shape and size of the wire or element is determined by what type of signal you wish to receive.
TV antennas have two types of elements, elements that receive the signal and turn it into electrical current to be picked up and amplified by the TV and elements that reflect or block signals that we want to double up on or block.
The DIY HDTV antenna will not contain the reflecting or blocking elements because that takes big bucks in research and development to design. But the receiving elements are very simple to design. They use straight forward formulas to determine the size of the element and the shape is a straight horizontal line. So once we figure out the size of the wire or element we need we will be ready to fly.
To figure out the size of the element we need we first need to know what frequencies we are going to be working with.
How to Figure the Length of Antenna Elements
The frequency will determine the length of the antenna element. You can choose from a quarter or half wave length element.
To find the frequency of the channel or channels you wish to watch go here: North American television frequencies
Once you have found the frequency of the channels you wish to watch use the formulas below to determine the length of the element for your antenna.
For a quarter wave antenna use the formula below.
For a half wave antenna use the formula below.
For example ME TV San Diego operates at a frequency of 180 to 186 MHz so lets pick an in between frequency of that which is 183MHz or 183 megahertz or 183 million cycles per second. Now lets figure for quarter wave.
So now cut two lengths of thick, single strand, wire to 1 foot 3 inches to be used on both sides of the antenna. To get a stronger signal use the half wave formula.
Constructing the Antenna
The picture above is a finished digital HDTV antenna made out of PC pipe.
There are two elements, my two favorite channels, made by tying The correct length of wire to a PC pipe and connecting them on top of each other and then securing them to the base.
Each side of the antenna has a complete element, one that connects to each connection of the 75 ohm antenna transformer as shown below.
The image below shows how I tied the two elements together. My favorite channels are at both ends of the frequency range so I end up getting all the channels available. The elements don't need to be exact just close for weak channels, strong channels will come through fine with elements that are in the general range.
When building your HDTV DIY antenna you will have to use your imagination a bit to come up with a design that will use the parts you have at hand, but for the design of the elements simple use the formulas given above. Strong channels, you will discover, will come in with just a dangling wire.
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