Hardware ~ Proper Wiring

Read these instructions carefully and follow them! You may run into all kinds of strange problems, crashes, unstabilites, packetloss, bad blocks and glitches if you don't!

YOU NEED TO SUPPLY BOTH THE RASPBERRY PI AND THE WIFI CARDS WITH STABLE 5 VOLTS!

use short wires
use wires with proper gauge, 20AWG (0.5mm²) is recommended
solder everything, avoid any USB cables or plugs, often they are of questionable quality, wires are too thin and connectors fit too losely and can't cope with vibrations/shocks
If you don't want or can solder directly to the card (for example on the Alfa AWUS036NHA, solder pads are very small), use a a USB cable and cut it off right behind the connector, then solder thicker wires to it (or directly to the Pi). Another alternative is to buy DIY USB connectors and solder cables to the conenctors directly.
use a quality BEC which can handle the load, depending on number and type of cards and Raspberrys used, current consumption can be as high as 3A for short peak periods.
consider adding low-ESR electrolytic caps near the wifi cards and Pi
do not use USB power banks, often they're of questionable quality and cannot deliver the advertised current
do not use the micro USB socket for power supply, apart from the drawbacks of the micro USB connector itself, on the Pi1/2/3 (as well as Pi1A+ and Pi3A+) there is a polyfuse in the current-path which lowers voltage and limits current which can lead to issues and instabilitues. If you want to power the Pi through the testpads at the bottom, make sure you use the testpads that are after the polyfuse (search Raspberry forum for details)
power through the GPIO pins
make sure the camera cable is properly seated on both ends
secure the camera cable with some tape or a drop of hotglue
make sure the Raspberry and wifi cards don't get hot, consider heatsinks
Keep the antenna away from the camera and camera cable
The Raspberry (and/or maybe the cam and it's cable, needs to be further investigated) seem to affect both 433Mhz,868Mhz LRS and also GPS reception, consider some seperation or shielding of the components