This is an 8-element collinear antenna made from LMR 400 coaxial cable. The first and last elements are 1/4 wavelength, while the others are 1/2 wavelength, adjusted for the velocity factor. The entire assembly is housed inside a 3/4" PVC pipe.

The results, shown in the images below, exceeded my expectations—I’m very satisfied with its performance.

I built this antenna specifically to feed data to FlightAware using a Raspberry Pi and a FlightAware dongle. You can view my real-time results here.