ENG-CANSAT-ANTENNA
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.
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.
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:
A PCB SMA connector is looking to this:
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.
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
The antenna lengths and spacing are depending on the wavelength to capture.
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.
Resource
- Yagi Uda Antenna (elprocus.com)
- Advantages & disadvantages of YAGI antenna (rfwireless-world.com)
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.
Getting Help for Antenna
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.
A yellow mark indicates the Radio Amateur clubs.
Written by Meurisse D. from MC Hobby - License: CC-SA-BY.