Dimensions of the Can Matter

Each radio frequency has a different wavelength.  The wavelength of a signal is the velocity of the wave divided by the frequency.  If you can, imagine you can create waves in a small pool.  The velocity is the rate at which the wave changes position.  The frequency is how many waves you can make in x amount of time.  The wavelength will be the distance between each wave you produce.

Now imagine you want to catch some of those waves in an aluminium can.  If you make really large waves in the water but have a tiny can, you won’t catch many, or they will just break up.  If you can perfectly match the size of your waves to fit inside the can, you will get capture the most water, or in our case, a wireless signal.  The only difference is that radio waves are invisible.  In order to find out the right size of the can, we need to do some maths.

Guidelines to Cantenna Dimensions

There are a few basic guidelines to follow when making a cantenna.  This will also help conceptualize what to do when making it or if you are modifying the can for a different frequency.

  • The length of the can should be longer than 3/4 of the wavelength
  • The diameter of the can should be longer than 1/2 of the wavelength
  • The copper element should be approximately 1/4 of the wavelength
  • The copper element should be x millimeters away from the back of the can (rear standoff)–this is based off the overall diameter of the can.  Use this calculator to determine this

There is an online calculator, which will help you determine the dimensions of your cantenna.

Formula for Calculating the Wavelength

First, it is important to know that radio waves travel at the speed of light, which is about 300 Mega meters (Mm) per second (the exact speed is 299,792,458  meters/sec).  For the purposes of an easy-to-remember formula, I rounded up and converted meters to Mega meters.

TinyURL for this post: https://tinyurl.com/y3t6vb4g

Sorry, The Comment Form Is Temporarily Closed At This Time