It's a type of antenna, named after one of the guys that invented it. It typically consists of a driven element (that the lead-in cable connects to), one or more "reflector" elements, longer than the driven element, located behind it, and several "director" elements, shorter than the driven element, placed in front. For TV, it is used for the UHF band, and looks like a reverse arrowhead. The other common UHF band antenna is the co-planar folded dipole array, or "bow tie" antenna.
VHF antennas are usually another type, called log-periodic, which look a little like Yagi's, and are mistakenly called Yagi's by some people.
Sorry. I didn't mean to be cryptic. I can't add better explanations than those above other than to draw a picture. My Yagi from the side looks like this, it is pointing to the right and connected to the mast in the middle:
I have the above-mentioned Channel Master 4248, which is a total of 80". Luckily, my house was pointed the "right" direction so that the 80" fits in my attic. The 4248 is about 3' tall, plus the mast. I got it online at www.consumerdirect.com for about $50 total, delivered in something like 3 days. My local radio shack didn't have one in stock. I think that Radio Shack carries smaller ones, but stock is questionable.
I have to go along with Barry on this one! Though you might have a VHF yagi, but it would only work effectively for one channel frequency. The traditional VHF antennae that most people have on their rooftop are broadbanded log-periodic. These antennae are often mistakenly refered to as Yagi! By-the-way the Yagi antenna was invented by Professor Uda, but was credited to Hidetsugu Yagi, a Japanese physicist, because of his English translation of the idea.
I did say "usually" for VHF antennas. Yes, there are single channel VHF Yagis. There are even Yagis that cover the VHF low band (2-6) or the high band (7-13). But there's a big gap between channels 6 & 7, filled with all sorts of things such as FM radio, police and fire VHF bands, etc. As a result, there's a huge frequency spread, ratio-wise, between channels 2 and 13 -- a ratio of 4:1. It's difficult to build a Yagi to cover this range, so all-band VHF antennas are usually based on a "frequency independent" design such as log periodic.
You have a right to install OTA and dish antennas on property under your control.
To clairfy the use of 'broadband' and 'log periodic' terms:
I have built a small, simple yagi with a broadband active element that has excellent gain across the UHF spectrum and use it for DTV reception indoors and outdoors. It is by no means a log periodic, but is a broadband antenna due to the feed design. There is only one 'active' element.
A log periodic antenna works in having different elements behave as 'active' or 'parasitic', depending on the frequency involved. The Silver Sensor UHF antenna is a log periodic antenna - the rear element becomes more of an active element at lower frequencies, but looks like a parasitic reflector at higher frequencies.
Log periodic antennas have low gain, but are very broadbanded. They also have less then optimal sidelobe performance and front-to-back ratio.
A folded dipole with open wire transmission line is a broadband antenna, too. But it's not a log periodic or a yagi.
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