ubuntu-au Digest, Vol 48, Issue 11

[Steve Pagratis]

Why make one when you can buy for just $30

I used to make antennas to but when local suppliers do them cheap, id rather
be drinking.
http://wifitech.com.au/catalog/index.php/cPath/33

Steve 

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Today's Topics:

   1. 850 MHz Wireless Broadband Modem Antenna (Geoffrey)


----------------------------------------------------------------------

Message: 1
Date: Fri, 12 Feb 2010 17:43:38 +1000
From: Geoffrey <gcombes4 at bigpond.com>
Subject: 850 MHz Wireless Broadband Modem Antenna
To: Ubuntu-AU <ubuntu-au at lists.ubuntu.com>
Message-ID: <1265960618.2430.34.camel at geoffrey-desktop>
Content-Type: text/plain; charset="UTF-8"

Recently I built and tested a home-made antenna for the wireless broadband
modem given to me by Telstra Bigpond (Maxon BP3-EXT). The Bigpond software
indicates signal level with five vertical bars. Using the modem antennas
(there are two, a primary and a secondary) signal level was usually 3
bars,sometimes 2 (<3 is poor). With the new antenna (fitted in place of the
modem's primary antenna) level is always at the maximum of 5. The higher
signal level should give fewer packet errors and therefore faster overall
data transfer.
The antenna consists of two quad (full-wave) loops made from cupper wire
each connected in parallel and mounted above an aluminium reflector plate. A
soldering iron is needed to fabricated the wire and to connect coaxial
cable.
The design frequency was about 850 MHz based on the quarter wave antennas
used by the modem. Because of the reflector the quad dimensions are smaller
than those calculated for free-space conditions. The actual dimensions were
arrived at by testing with an RF Vector Network Analyser (VNA)and the
distance to the reflector adjusted for best SWR (1.3). The impedance of the
antennas was close to 50 ohm. The antenna was connected to the modem via a
metre of 50 ohm high-quality coax suitable for the modem's SMA connector.
This antenna is not a new design. I have seen one made using two diamond
quads. My antenna is two square quads; equally good and simpler to make.
Email me if you are interested in looking at a drawing of the design and a
picture. I have drawings as .odg and .xsf files. If required I could send a
.jpg file.





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End of ubuntu-au Digest, Vol 48, Issue 11
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