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--- guides:payloadantenna [2013/07/30 13:01] – upu
+++ 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 S_Mark http://www.stratodean.co.uk/search/label/Components):
-{{:guides:payloadantenna1.jpg?400}}
-{{:guides:payloadantenna2.jpg?400}}
-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]]
-====== Step by Step Build ======
-You will need :
-Wire cutters, sharp blade, ruler, [[http://www.ebay.co.uk/sch/i.html?_trksid=p2050601.m570.l1313.TR2.TRC0.A0.X1%2F0.6mm&_nkw=1%2F0.6mm&_sacat=0&_from=R40|Single core wire]], RG174 coax. Example uses [[http://ava.upuaut.net/store/index.php?route=product/product&path=71_66&product_id=88|RG174 to SMA pig tail from HAB Supplies.]], Solder and Soldering iron.