File:Hogg horn antennas.jpg
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DescriptionHogg horn antennas.jpg |
English: Microwave horn antennas on the roof of a telephone switching center near Madison St. and 17th Ave, Capitol Hill, Seattle, Washington state, USA. This is part of the TD-2 AT&T Long Lines microwave relay system, created in 1955 to relay telephone calls, television shows, and other data from point to point in the US. The system uses C-band frequencies in two bands at 4 and 6 GHz. This type of antenna is called a Hogg or horn-reflector antenna, invented by Albert Beck and Harald Friis in 1941 and developed at Bell Labs in the 1950s. They consist of a vertical flaring metal horn fed with a 2.8 in. circular waveguide, with a reflector mounted in the mouth at a 45° angle, so the beam of microwaves is emitted horizontally (the aperture of these antennas, facing right, is covered by a plastic sheet to keep out rain). The reflector is a segment of a parabolic reflector, so the antenna is equivalent to a parabolic antenna fed off-axis. The advantage of this type of antenna over an ordinary parabolic (dish) antenna is that it has very small sidelobes; that is it picks up very little radiation from directions outside its main beam axis. This allows the same microwave frequencies to be used by several nearby antennas without interfering with each other. These AT&T model KS-15676 L9 antennas have a gain of about 43 dBi and produce a beamwidth (HPBW) of about 1° at 6 GHz. Backlobe sensitivity is -60 to -80 dBi. (From KS-15676 Horn Reflector Antenna Description, Bell System standards, AT&T Also: Bell Labs Record Nov 1955)
Microwave links like this use 2 antennas (one transmitting and one receiving) to send a beam of microwaves of a few watts power to a similar station about 30 miles away. Each antenna can carry tens of thousands of telephone calls. |
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This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: Cropped image, brightened to bring out detail. The original can be viewed here: Seattle-Capitol-Hill-Radio-Antennas-3357.jpg: . Modifications made by Chetvorno.
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This image is a derivative work of the following images:
- File:Seattle-Capitol-Hill-Radio-Antennas-3357.jpg licensed with Cc-by-sa-2.5,2.0,1.0, Cc-by-sa-3.0-migrated, GFDL
- 2007-04-21T00:54:38Z Vmenkov 2048x1536 (1169188 Bytes) ==Summary== {{Information |Description={{en|A radio station (?) near Madison St and 17th Ave, Capitol Hill, Seattle}} |Source=Own photo |Date=2007-Mar-10 |Author=[[User:Vmenkov|Vladimir Menkov]] |Permission={{self2|GFDL|cc-b
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current | 02:37, 12 November 2010 | 699 × 951 (154 KB) | wikimediacommons>Chetvorno | {{Information |Description={{en|Antennas on the roof of a microwave relay station near Madison St. and 17th Ave, Capitol Hill, Seattle, Washington state, USA.}} This is part of a system created by AT&T to relay telephone calls and other data from point t |
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Camera manufacturer | CASIO COMPUTER CO.,LTD |
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Camera model | EX-Z50 |
Exposure time | 1/160 sec (0.00625) |
F-number | f/4.8 |
Date and time of data generation | 16:29, 11 March 2007 |
Lens focal length | 17.4 mm |
Orientation | Normal |
Horizontal resolution | 72 dpi |
Vertical resolution | 72 dpi |
Software used | 0.90 |
File change date and time | 16:29, 11 March 2007 |
Y and C positioning | Centered |
Exposure Program | Normal program |
Exif version | 2.21 |
Date and time of digitizing | 16:29, 11 March 2007 |
Image compression mode | 3.203125 |
Exposure bias | 0 |
Maximum land aperture | 2.8 APEX (f/2.64) |
Metering mode | Pattern |
Light source | Cloudy weather |
Flash | Flash did not fire, auto mode |
Color space | sRGB |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Manual white balance |
Focal length in 35 mm film | 105 mm |
Scene capture type | Standard |
Contrast | Normal |
Saturation | Normal |
Sharpness | Normal |
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