Having a working video stream from the rocket involved quite some small tests and calculation before we knew how to implement the system software and hardware wise.
In the past, we’ve used GoPro’s as cameras in the rocket, which turned out to be a nightmare control-wise. This year, we are using four RunCams (a different brand but also small action cameras) to create a 360 degrees view (three times 120 degrees) and one downwards-facing camera to capture Earth.
So, you first start with setting up a link budget: how much power and gain do you need to have an acceptable range of power at the receiver? Important factors are, for example, expected distance and operating frequency (in our case 2.4 GHz). The link budget showed that we needed a power amplifier (PA) to boost the output power of the transmitter from ~700 mW to ~4 W to have an acceptable receiver power of -94 dBm (less than a picowatt..) in addition to the gain we have from antennas that transmit and receive.
We tested this using a huge series of attenuators to replicate the attenuation that would be present due to the rocket flying away up to great altitudes. We were still able to see clear video on the screen with over 130 dB of attenuation, which is a success. We still have to discover though, what the noise level at the launch site will be…
by Hans Okkerman