antenna-theory.com

[rtrex]

Hi to you all

I have been playing around with home made antennas since 2004.
I use designs taken from the internet .
I have made two double face 2.4ghz wave-guides, one with 8 slots on each side(8+8 ) and one with 16 (16+16) .(check the link below)
http://wavetenna.blogspot.pt/2007/09/sloted-waveguide-17-dbi.html

The are very good in gain and work very good even without being able to measure vsrw,gain,etc, because i don’t have instruments to do it.
I took the desig from here http://nuke.freenet-antennas.com.au/images/WGWaveguideCalculator.zip

But i am thinking in building a new waveguide.

I have found some design and even commercial antennas but with small different features like feed with offset from the centre and some screws to tune vsrw .
My source for this design is the web page, http://www.wikarekare.org/Antenna/8+8Waveguide.html

I know if i want sloted wavegide to have a perfect omni pattern the "short side"(see link wikarekare.org) needs to be very small like 2.0~2.5 cm or have "wings".
http://www.digdice.com/wp-content/uploads/2008/02/cms-array.jpg

My big problem is the feed because i use a 1/4 wavelength coper wire (3.1cm for 2.4ghz) so it does not fit inside the pipe.

What other type of feeds can i use for 2.4ghz that fit inside a 2.5 cm pipe .

Thank you.

Edit: I had problem because of a link on the post som of you may have seen the post empty.

[Schubert]

I think you are saying that for omni pattern, the height of the waveguide should be 2-2.5cm. I'm not sure that's an actual rule, or at least I've never heard of that or know why it should work.

Regardless, there are some tricks you can use to get your 3.1cm in the waveguide:

(1) Meander the wire - instead of being straight up just bend it horizontally
(2) Capacitively load it - use a wire, but put a "metal cap" (like something the size of a dime) on top, which will increase the effective size of your antenna and enable a shorter physical size
(3) Use a smaller wire anyway and then just use impedance matching to get it to work

[rtrex]

[admin]

rtrex's last comment should be ignored:

I've asked a friend of mine quite a while ago to simulate a 100x25mm for 2.4ghz waveguide and the pattern was perfectly omni.

RF/antenna engineering is too hard to have arguments like that carry any weight. No slotted waveguide will be perfectly omni by any measure unless you don't have a precise measurement methodology.