Just modified a Raspberry Pi 3 to accept an external WiFi/Bluetooth antenna via U-FL socket.
After successfully testing of my G7RGQ antenna here my built details:
With above dimensions the antenna is tuned to about -22dB return loss at 1090MHz when placed inside the PVC tube.
I took the opportunity for some experiments with gain settings in dump1090-fa while testing a new built antenna for the ADSB receiver. I compared my previously built QFH antenna to a G7RGQ omni directional antenna that I built last week. Second object of test was a 10m active USB cable (from Amazon).
Here is another one. Huge thing this time, designed for 433MHz, polarization RHCP. For dimensions etc. see design description below.
Here is another quadrifilar helix antenna design, this time for ADSB (aircraft mode-S transponder) reception at 1090 MHz. Unlike other antenna types this antenna has a spherical coverage with 120° 3dB beamwidth and estimated peak gain of 4.6dBi at 1090MHz.