antenna-theory.com

[franzellin]

as shown on the market there are these antennas, for instance 80cm long, 10 cm width and 2.5cm tick, they can have horizontal slots (vertical polarisation) or vertical slots (horizontally polarized) saying 17 dBi gain

A) some are sold with an 180 degrees irradiation in 1 direction and ca.6 degrees in the opposite
B) others are sold with 360 degrees irradiation and 6 degrees in the opposite
both have the same dimensions

Looking your video i deduct that A could be a cavity backed slot antenna but for the second one B, I have the following questions:

1? how is Type B build, are there 2 slotted panels mounted at a distance of 2.5 cm and a reflector between them?
2? or is it only 1 panel ?
3? if there are 2 slotted panels, the little distance between them, 2.5 cm, does not interfere in the irradiation?
4? the antenna is attacched at the bottom to the cable, and in your video you explained that the current flows in certain direction , but I do not understand how the current could flow in a 80 cm long antenna with for instance 10 slots and 20 if they are on 2 sides

could you please give further technicals details about this kind of antenna?

thanks renato