Ground Plane Antenna

After i bought a RTL-SDR usb device i tried to listen some radio signals, however the antenna sold with the device wasn't so good for me, so I decided to create my own antenna for a specific frequency.
The ground plane antenna was the most simple solution for me so i went to the hardware store to buy the stuff I need to assembly everything.

B.O.M.
->5 x 1mt 6mm diameter alluminium rod;
->8 x M4 12mm long screws;
->4 x M4 20mm long screws;
->5 x M3 screws;
->80cm 20mm diameter PVC pipe;
->Antenna cable (i'm using common 75ohm 5.7mm diameter TV/SAT cable);
->Connector (F-type connector in my case)

I've used this site to calculate the lenght of each metal element:
https://m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/