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--- guides:payloadantenna [2013/06/11 09:09] – chrisstubbs
+++ guides:payloadantenna [2014/12/07 14:59] (current) – created lz1dev
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-====== Payload Antenna ======
+Moved to [[guides:payload_antenna|Payload Antenna]]
-The 1/4 wave ground plane antenna seems to be the most common antenna for use on payloads. Its omnidirectional radiation pattern makes it suitable for use on a payload as it will emit equal radio power in the direction of all receivers.
-A typical 1/4 wave payload antenna can be constructed from stripping a length of insulation from some 50 ohm coaxial cable (RG58). The copper braid can then be separated into 4 strands and secured in an X formation by either using tape to the bottom of your payload box, straws, or soldering solid core wire to the braid.
-The length of exposed core (driven element) and braid (radial) is calculated by the speed of light / frequency.
-This will give you your wavelength (as c=fλ). Dividing this number by 4 will give you 1/4 of your wavelength as required for a 1/4 wave antenna. However it should be noted that the velocity of a wave is slightly slower through an antenna than it would be in free space. So for this reason you should multiply your calculated length by 0.95
-The core of your coaxial cable will act as the driven element of the antenna. If your cable came off a reel it will probably want to stay in a curved shape. Supporting the driven element of the antenna by placing it inside a drinking straw will prevent this, and should also give some support if the payload has a rough landing.
-Example images of a 1/4 wave antenna (from http://www.stratodean.co.uk/search/label/Components):
-[[http://1.bp.blogspot.com/-mF2Kyo6-8GU/ULPJNIxeexI/AAAAAAAAA7I/IWLYiqOTld0/s1600/IMG_1638.JPG]]
-[[http://4.bp.blogspot.com/-R5zyNoIaHU4/UWrc2n6P6zI/AAAAAAAABTk/xsqZ0TyUdeU/s1600/IMG_2021.JPG]]
-Some good information about antenna design and propagation can be found at [[http://www.idc-online.com/technical_references/pdfs/electronic_engineering/Antennas_and_Propagation.pdf]]