Differences

This shows you the differences between two versions of the page.

--- guides:payloadantenna [2013/07/30 13:42] – upu
+++ guides:payloadantenna [2014/12/07 14:59] (current) – created lz1dev
@@ Line 1: / Line 1: @@
-====== 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 :
-{{:guides:img_1927.jpg?500|}}
-Step 1 : Trim the insulation from the coax.
-Measure 170mm from the bare end of the coax and cut the insulation without damaging the braid inside. Gently roll the blade over the cable :
-{{:guides:qwave2.jpg?500|}}
-Its important at this point not to cut the braid inside.
-Step 2 : Carefully Remove the insulation back to the end of the coax :
-{{:guides:qwave3.jpg?350|}}{{:guides:qwave4.jpg?350|}}
-The easiest way to do this is to roll the knife around then carefully cut lengthways and remove the insulation in segements.
-Step 3 : Leaving 5mm of braid cut the braid and remove :
-{{:guides:qwave5.jpg?350|}}{{:guides:qwave6.jpg?350|}}
-Step 4 : Tin the Remaining Braid :
-Make the remaining braid into two stumps and tin :
-{{:guides:qwave7.jpg?500|}}
-This is the radiating element. Put this to one side.
-Step 5 : Prepare the radials
-Cut two lengths of single core wire about 350mm long. Mark the center point with a pen and then remove about 25mm of insulation from the center :
-{{:guides:qwave8.jpg?500|}}
-Again this is easiest by gently rolling the wire on the edge of a blade and then cutting lengthways and removing the insulation.
-Step 6 : Twist Together
-Using a pen or large nail as a former place the wires around and twist together. Then apply solder to secure them :
-{{:guides:qwave9.jpg?350|}}{{:guides:qwave10.jpg?350|}}
-Step 7 : Connect the two sections
-Slide the coax part through the small hole in the center of the radial section. Solder in place :
-{{:guides:qwave11.jpg?500|}}
-Step 8 : Trim Radiating element and radials
-From the point where the shield ends measure the radiating element and trim @ 164mm. This value is important :
-{{:guides:qwave12.jpg?500|}}
-Repeat with the radials.
-Congratulations you've made a light weight 1/4 wave antenna for 433Mhz. It is recommended you secure and straighten the radials and radiating element using straws :
-{{:guides:qwave13.jpg?500|}}
-You can trim the straws down but take care not to snip the elements inside. The radials form a ground plane and this can be constructed into the base of the payload. The radiating element should face downwards. The length of the coax from the SMA plug to the start of the antenna isn't important though its suggested its kept as short as possible.
-You don't need a coax with an SMA plug on it you can solder the other end directly to the board.