antenna ??????????????

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danbob
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antenna ??????????????

Post by danbob » Fri Apr 06, 2007 11:29 pm

what is this antenna for?
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stevech
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Post by stevech » Fri Apr 06, 2007 11:45 pm

looks like a high gain UHF TV receiver antenna to me. Perhaps someone's HD-TV

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Externet
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Post by Externet » Fri Apr 06, 2007 11:56 pm

Hi.
It is to transmit/receive anything on the frequency it is made for; looks like a directional colineal dipole phased array.
The mesh at its back is just a reflector, works like a mirror. By the size of the grid it is not for microwaves. Seems more like VHF, could be a 3m broadcaster/link.
The 4 active rabbit-ear dipoles can clearly be seen phased and in parallel to a single coaxial line.
If every dipole was 200 Ohms impedance, the total would be 50 Ohms.
The TX/RX direction is towards the picture observer.
Miguel

rshayes
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Post by rshayes » Sat Apr 07, 2007 5:52 am

It looks like a UHF TV antenna. The gain is probably in the 6 to 8 db range, since the matching and phasing of the elements is probably a comprimise. The feed point impedance is probably in the neighborhood of 300 ohms, to match the old 300 ohm twin lead. You can see a balun transformer on the end of the coax. This provides an unbalanced to balanced conversion and also converts between the 75 ohm coax and the 300 ohm feedpoint impedance. The "V" shaped elements are used to broaden the bandwidth compared to simple dipole elements.

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dacflyer
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Post by dacflyer » Sat Apr 07, 2007 6:33 pm

its just a common VHF / FM antenna.. i used to have one years ago on a rotor it worked great for FM radio which i used it for..


here is a simmelar one i bought not long ago,, it works well also.. it is a all-in-one antenna UHF / VHF / FM / HDTV
and get this... just 1 cable... the signal and rotor all work thru 1 coax
wasn't bad at all for $20.00
only down side is you have to assemble it...

http://cgi.ebay.com/HDTV-VHF-UHF-FM-SCA ... dZViewItem

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