[sleeve colinear ant] Guess its freq and its gain - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

Below are the old forum threads, including responses to the original posts.
-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews
 -- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

Guest
 Post subject: [sleeve colinear ant] Guess its freq and its gain
Posted: Mon Jan 30, 2006 12:16 pm 
Hello there!

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 :
Image

I mesured the different elements:
section (2 tubes + empty space): 90.8mm
space between sections: 1mm washer
space between tubes: 34mm
10 sections
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...

Thanks, /Lapi.

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.



Posted  11/12/2012