I'd like to ask you a riddle. I bought this antenna on eBay and it is sensed to work in the 2.4GHz band (wifi). But as its performance was really poor, I dismantled it.
Its design is based on the so-called sleeve colinear antenna
, like the one I found on the net :
I mesured the different elements:
section (2 tubes + empty space): 90.8mm
space between sections: 1mm washer
space between tubes: 34mm
outer tube diam: 28,4mm (no dielectric filled, air only)
inner tube diam: ~28mm
top whip: 41mm
coax diameter: 3.8mm
I guess the oscillation starts from the bottom tube. But what parts do radiate: the tubes or the inner coax?
Have you found its fundamental frequency? I'm longing for your answers...
PS: does anybody know how to model this kind of antenna in 4nec2? Especially for the tube and coax. I'm quite newbie at this software.