Archived from groups: alt.internet.wireless (
More info?)
On 29 Dec 2004 06:40:31 -0800, smogkiller2004@yahoo.com wrote:
>First, what is "DBI" vs. "DB"?
dB or decibels is a ratio. For power, it's
dB = 10 * log (ratio)
Decibel means 1/10th of a Bell, which nobody uses.
When you're talking about gain or loss, the common term is dB.
>Techno-Labs uses "DBi" not the more common "db" terminology.
dBi is decibels over an isotropic radiator. It's the common term in
antenna design. An isotropic radiator is a mythical point source
radiator with a gain of 0dBi. The antenna gain, in dBi, is the
increase in signal strength produced by the antenna when compared to
an isotropic radiator.
Since an isotropic radiator cannot be built and exists only in antenna
modeling programs, some people prefer dBd or decibels over a dipole
antenna. In theory, a dipole has a gain of 2.15dBi, so the two
reference levels can be abused interchanegably.
>Anybody have real-world experience with their small, triangular,
>Mega-Wave directional antanna? Any reviews posted anywhere?
>http://www.technolab-inc.com/cgi-local/ppalstore/ppalstore.cgi?product=antennasd&cart_id=7142803_7409921
Not with that particular brand, but the antenna itself is common
enough. It's a log periodic antenna on polysulfone circuit board. It
has enormous bandwidth (which you don't really need) and a gain of
about 4dBi (which is quite low). Normally, such antennas are used for
broadband interference and radiation testing, lab work, dish feeds,
cellular panel antennas, ATV, and exotic modulation schemes where the
group delay at the band edges is critical.
The web page claims 12dBi gain, which methinks is rather optimistic.
A quick check with 4NEC2 shows 4dBi gain. It's also a common antenna:
http://www.btinternet.com/~jewell/PCB.html
Well, that one is on FR4/G10 which has much more loss than polysulfone
circuit board.
Anyways, not recommended due to lack of suitable gain.
--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558
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