Here you get an brief overview about the involved hardware.
There are different type of emitters on the market which mainly split up into two groups: coded and VHF tags.
Coded tags send for example every 5 seconds a set of bursts. Those sets of bursts contain for example 4 single bursts in a very short time. By calculating the time difference between the 4 bursts, one can identify the tag. Normally the coded tags work on one frequency (typically 150.1 MHz).
VHF tags send one long burst (about 20 ms) every second (can vary too) on a special frequency. The frequency is then used to identify the tag.
radio-tracking.eu supports both tags but is more specialized on the VHF tags.
Again there are basically two types of antennas: omnidirectional and directional antennas. The directional has a "preferred" direction – so if you point it straight at the transmitter's direction you will get highest signal strength. Whereas an omnidirectional antenna has no "preferred" direction.
radio-trackin.eu makes use of both antenna types. On a map you either see a circle around the position of the antenna or a cone indicating the orientation of the antenna.
And yet again, there are two types of receivers: analog receivers which are set to match the frequency of the transmitter and demodulates the radio wave to hear a "beep"; digital usb receivers (also known as software defined radios (SDR)) which, instead of receiving one single frequency, cover a whole frequency range depending on their sample rate. Software is used to listen to a single frequency or to monitor a whole frequency range (spectrogram).
radio-tracking.eu uses digital usb receivers to monitor automatically a frequency range up to 1 MHz.
Here we have three options: the Raspberry Pi 3 B, the newer (and slightly faster) Raspberry Pi 3 B+ or the Raspberry Pi Zero W. The Raspberry Pi 3 B/B+ supports up to four receivers whereas the Raspberry Pi Zero W only supports one. The main advantage of the Raspberry Pi Zero W is that it uses less power and thus runs longer. The software also runs on older Raspberry Pis but is not recommended.
radio-tracking.eu supports the Raspberry Pi 3 B+ (only Version 4 "paur" of the software), the Raspberry Pi 3 B (Software-Version 3 "nactalus" and Version 4 "paur") and Raspberry Pi Zero W (only Software-Version 3 "nyctalus").
We have three options to power the system (micro usb power cable goes into the raspberry pi and the usb receiver is powered via the pi): power bank, 12V car battery and transformer, or electrical socket using a usb charger. The first two options can be combined with a solar panel to extend run time.
radio-tracking.eu only needs somehow a 5V supply that doesn't produce a lot of noise.
Cables and Plugs
Two types of cables are involved: antenna and power cables. Both need to be well shielded to avoid receiving extraneous noise and thus be able to also "hear" weak signals. For the antenna plugs we try to limit it to a male N-Plug to connect the antenna (waterproof) and a male SMA to connect it to the usb-receiver. The vewer plugs and cables are involved, the lower the signal loss.
radio-tracking.eu tries to limit the use of cables and plugs to have a better signal and less noise.
Electrical equipment produces noise, especially low-priced units. One way to avoid receiving the electrical noise of your own equipment is to electro-magnetically shield parts of it and to use the recommended material.
radio-tracking.eu uses an aluminium case to shield the raspberry pi and ferrit cores to shield the usb cables.
To remotely connect and operate a station the 2G/3G/4G Network can be used. A hotspot creates a local WiFi-Network and several raspberry pis can be connected to it. To connect to the raspberry pis, a certificate is required which can be ordered at radio-tracking.eu.
The electronical equipment needs to be protected by a waterproof box – radio-tracking.eu shows one possible setup, there are many more suitable alternatives. If you do find a good solution please send a picture and maybe a link of the manufactures to allow us to show these on the website.
Two options: fiber glass (light weight) and aluminium (heavy but solid).