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The ideal Length can be calculated with the following formula:
 
The ideal Length can be calculated with the following formula:
  
  <nowiki>     c
+
  <nowiki>       c
 
L = -------
 
L = -------
 
     4 x f </nowiki>
 
     4 x f </nowiki>
 +
Where:
 +
* '''c''' : is the light speed
 +
* '''f''' : the frequency for the antenna
 +
* 4 : because it's a quarter length antenna.
 +
 +
So
 +
 +
When using such antenna, you have to think about the polarisation of your signal.
 +
 +
=== Other Antenna ===
 +
We encourage you to search antenna with better performance.
  
 
== Getting Help from Radio Amateur ==
 
== Getting Help from Radio Amateur ==

Version du 4 novembre 2018 à 00:12

Introduction

What ever you do, the antenna is always one of the most sensitive component when working in the radio area.

The following schema shows how to wire the RFM69HCW to transmit data.

ENG-CANSAT-RFM69HCW-TEST-00.jpg

As you can see, the antenna is made of a simple wire.

Remove the wire and the data would not transmit at 1 meter of distance, even on the same desk!

Remember, the antenna is the key to transmit data over a long distance!

Antenna connector

The radio modules usually offer a spot to solder antenna.

With the RFM69HCW the antenna spot allow you to connect an antenna in 3 different ways.

ENG-CANSAT-RFM69HCW-Antenna.png

Later on, you would focus on antenna choice:

  • A wire inside the antenna hole (also said a wire dipole or simple dipole).
  • A µFl connector to plug antenna.
  • A PCB SMA connector also to plug other kind of antenna.

The cheapest antenna is the wire antenna (simple dipole) and the best option is the SMA connector (also mode heavy).

The µFl connector (also named uFl) is looking to this:

ENG-CANSAT-RFM69HCW-TEST-uFL-connector.jpg

A PCB SMA connector is looking to this:

ENG-CANSAT-RFM69HCW-TEST-SMA-connector.jpg

Yagi Antenna

While reading some resources on the QSO magazine (Magazine from Belgian Radio Amateur Association written in dutch and french), we did discover a Yagi Antenna tuned for 433Mhz.

ENG-CANSAT-ANTENNA-10.png
Source: QSO Magazine via this publication - click to enlarge

This antenna was engineered from the "Cheap Yagy" (pdf), issue from the "Controlled Impedance 'Cheap' Antennas" article written by Kent Britain WASVJB.

A simple rule of three can be used to adapt the antenna to other frequencies (the antenna was already adapted from a 432 Mhz design).

6 or 11 elements

The Yagi antenna showed here upper does have 6 elements.

From a deeper read of the QSO magazines series, we learned that 6 elements Yagi can offer a gain up to 11.2 dBi.

It seems that the 11 elements Yagi (see original document) will double the gain. Whoaw!!!

About Yagi Antenna

Here some very basic information about Yagi antenna. It brings fundamental concepts that you will deal off with such antenna.

Radiation Pattern

The radiation pattern is the direction or directions where the signal will be emitted (or received).

So for a given transmission power, a directional antenna would send the signal further than an hemisphere antenna. Indeed, directional antenna would concentrate all the power is one direction where as hemisphere antenna would spread the same power all around.

The Yagi antenna does support several radiation pattern but "Yagi" is often used in place of "Directional Yagi".

  • Isotropic Antenna : radiate the same in all the direction.
  • Directional Antenna (or Beam Antenna) : radiate most of its power in one or more direction. This increase the performances in the direction while reducing the interference coming from the other directions.
  • Omni Directional antenna : uniformly radiates the power in one plan. With a directive pattern shape in perpendicular plane. This antenna radiates equally in all the directions and have some angle of elevation (dixit elprocus.com)
  • Hemispherical antenna : radiates one half of the hemisphere (the lower or the upper one)

Common Design

The antenna lengths and spacing are depending on the wavelength to capture.

ENG-CANSAT-ANTENNA-30.png
Source: design of Yagi Uda Antenna

  • Directors : used to drive the signal in the given direction. Those directors are usually shorter than driven element (about 5%).
  • Driven element : is the element that capture or emit the signal.
  • Reflector : reflect the signal toward (or coming from) the driven element. The reflector is larger than driven element (about 5%).

Because of the antenna design, the maximum of radiation is in the way of director.

ENG-CANSAT-ANTENNA-31.png

Needed Material

A cheap Yagi antenna could be realised with plastic material and some very tick wire.

ENG-CANSAT-ANTENNA-32.png

However, the standard Yagy Antenna (and the best ones) are made with aluminium pipes.

Resource

CanSat and Antenna

As specified by the CanSat settlement, everything should be contained within a defined volume (the Can).

So, the antenna should also fit into the volume.

However, once the can is released in the air, your project can deploy an antenna.

A well designed antenna for sending the data would also reduce the error ratio on the ground station.

Quarter WaveLength Antenna

It is possible to create a small antenna made of a simple thread of Wire.

The thickness is not especially critical but the length is very important.

The ideal Length can be calculated with the following formula:

       c
L = -------
     4 x f 

Where:

  • c : is the light speed
  • f : the frequency for the antenna
  • 4 : because it's a quarter length antenna.

So

When using such antenna, you have to think about the polarisation of your signal.

Other Antenna

We encourage you to search antenna with better performance.

Getting Help from Radio Amateur

Designing and testing an antenna for long distance communication is an intensive work.

You could find some help from our Radio Amateurs friends.

To locate a Radio Amateur Club near of your home then have a look the "Maker's Maps" owned at MC Hobby.

ENG-CANSAT-ANTENNA-20.png

A yellow mark indicates the Radio Amateur clubs.


Written by Meurisse D. from MC Hobby - License: CC-SA-BY.