[ Home ] [ Up ] [ Aviation Bits ] [ Webcam ] [ Pedals ]

Other antennae

Baby milk cantenna

Omni-directional

Can with conical horn

Self contained USB Cantenna

Parabolic Antenna

Baby milk Cantenna

Just a quickie made from an SMA Gold baby milk powder tin.  The length is supposedly too short to be particuarly good but the tin is very light, doesn't have the ribbed sides that the dog food tins do and has a much flatter base.  I also like the colours!  :-)

Ok, i'll be honest, I have turned into a junkie, eyeing up tins in supermarkets, wondering what they will perform like.  I have a large SMA tin which should be ready soon, once the baby has finished the contents!

Omni-directional

I have a need for an omni-directional antenna and thought that the plans at http://www.guerrilla.net/reference/antennas/2ghz_collinear_omni_lowpwr/ were about the most straightforward.  I'm not reproducing my build details since it's already covered in this link.

(It now appears that guerrilla.net has disappeared from the Internet but I have found a cached copy of the instructions so am now hosting the instructions here)

Low Power 5dBi Omni-directional antenna build plans

2.4GHz Co-linear Omni-directional antenna build plans

I bought my brass rods from McQuire Enterprises, a UK mail order model shop, http://www.modellers-supplies.co.uk/acatalog/Modeller_s_Supplies__Imperial_round_brass_tube_12__137.html

Attached to a 3' cranked mast for testing purposes, once again using the trusty suction cups on flexible stalks that come  with Halfords mobile phone holders.

Attached to the house with an SMC2652W Access Point in a weatherproof box

Can with conical horn

To further increase gain, a horn can be added to the front of the can.  This antenna is mostly cardboard, the can itself is a carboard with metal lining milk tub, the horn is made from aluminium backed cardboard.  This was obtained as an A0 size sheet from an art shop, nothing special!  To make a horn to suit the 92mm apeture of the milk tub, simply draw two concentric arcs using the following dimensions:-

Inner radius     =    85.2mm

Outer radius    =    316mm

Rotation angle    =    194 degrees.

These dimension should provide a gain of around 16dBi

In order to attempt to smooth out the junction between the can and the horn and to ensure electrical continuity, I used self adhesive, conductive copper tape.  Brief tests showed this antenna to produce the expected extra gain and significantly increased directivity.

Results

Click to enlarge!

On the left is the signal with just a dog food tin cantenna, the stronger signal is using the above cardboard horn!  The Orinoco client claims an excellent signal, Windows XP signal meter shows 4 bars and a signal strength of "Very Good"!  This signal strength is better than  I get 20m from the AP when inside the building housing it!  The trees in the way are now in full leaf too, I don't see how I can really improve on this.

In fact there's so much gain, I still got a usable signal with this antenna inside the Travelodge, simply stuck on to the TV and pointing through the walls:-