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How Can you Make a VHF TV Antenna for an Attic
wrote in message ... Hi - I need to receive VHF TV (channels 6,7,9,13) and would like to make a super-duper antenna for inside my attic. I would have thought that I could easily find (simple) instructions on the internet but can't. Does anybody have a simple idea that just uses wire (wire should be easy to attach in an attic). I'd like the answer to be YES, but it's NO.. If you wanted to make an antenna for just one channel, I'd say yes. I already did it for some guy who wanted a channel 2 antenna over a year ago. I've seen some instructions (mostly UHF or DTV) and some of them do calculations for wavelength (let's say 5 feet). It's a multi-step process. You have to look up the channel frequency for a TV channel. Then, you take the number 300 and divide it by the frequency. The result is the wavelength. The elements are then cut for approximately a half-wavelength. More details below, if you want 'em. Multi-channel antennas have multiple elements, all differing lengths. If you have one element, you can expect to receive one channel well and other channels maybe but not as well. A single channel antenna can be made of TV twinlead and attached to a piece of wood. It's called a "folded dipole." More below. And then, with no explanation, the guy just says "I made it 10 feet for better reception". So I ask, can I not then just use the entire length of my attic for super-duper reception? Nope. He's full of it to say that. The only thing that gets longer to make a better antenna is the boom, the center long rod of a long antenna, and it gets longer because additional elements are added to it to improve the performance. However, you have to know how many, how long and where to put them. That's why we study this stuff. Wire is cheap after all, and I only want to crawl up there once. Crawl up there once and bring a TV antenna with you ... a STORE-BOUGHT TV antenna. Hang it flat from the rafters. A balun is a little matching transformer with side-by-side wire connections on one side and a round coaxial cable connection on the other side. Picture he www.summitsource.com/images/products/COTRAN.jpg Most antennas have two screws for attaching one side of a balun. Connect your coaxial cable to the other side. Also, I see instructions that say you should aim the antenna without defining "aim". Do you align the wire in the direction of the transmission antenna, or should the wire by perpendicular? The outline of many TV antennas, viewed from above or below, resembles the outline of an arrowhead. That's it. The smaller elements are on the end that's nearer to the TV station. The signal arrives perpendicular to the alignment of the elements. http://www.radioshack.com/pwr/conten..._thumbnail.jpg is an antenna which illustrates the arrowhead concept. The stations are off to the right side in this picture. I have no idea whether the antenna in the picture is any good. If you make a single element antenna, you align it perpendicular with the arriving signal. These do work pretty well, by the way. http://www.wfu.edu/~matthews/misc/dipole.html has some step-by-step instructions for making a folded dipole with ordinary tools. One last thing: It's not beyond the realm of possibility to make one folded dipole attic antenna for Channel 6 and a second folded dipole attic antenna for Channel 9. The Channel 9 antenna just MIGHT also handle 7 and 13 if you're in a good reception area. You can cable both of them to the TV and switch between them. Sal |
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