Posts Tagged ‘Omnidirectional’

Stacking 4 ATMOS Antennas

Sunday, October 21st, 2007

Interesting post in zero wireless forum about stacking four atmos antennas.

The result looks very bizarre really :

here is the link :

http://www.zero13wireless.net/foro/showpost.php?p=21206&postcount=110

Alford Slot – Horizontal Omnidirectional Antenna

Thursday, September 13th, 2007


Alford Slot – Horizontal Omnidirectional Antenna working on HAM band – somewhere around 2.3ghz or 13cm.

Whit several words what is Alford Slot : this is circular pipe whit ONE LONG slot on it, feed by coax line coming from inside the tube.

Here is some photos :

Alford SlotAlford Slot

note pics are for lower frequency – typically for 1200Mhz, second shows that for low band this antenna can be made even from wire

The tutorial how to make this antenna is on this site : http://www.g8ajn.tv/23cms.htm and http://www.k5rmg.org/Alford-slot.html

Interesting about this antenna :

Omnidirectional paten

Horizontal polarization

Physically its circular – for me its important omni antenna to be circular – do not ask 🙂

Interesting feeding point of slot.

The design of this antenna is based on several tables or ready pre-calculated values.

Freq.
(MHz)
Slot Length
2.15 l
(inches)
Active
Circum.
0.40l
(inches)
Slot Width
0.016l
(inches)
Final
ant.
dia.
(inches)
902.1 28.25 5.20 0.190 ~1.72
1296 20.125 3.910 0.170 ~1.3
2304 10.688 2.120 0.090 ~0.7

active-circumference.gif

Here is some pictures from www.g8ajn.tv

cameradownload-071.jpgcameradownload-072.jpg

cutting the slot and ready feed points

Here is the interesting part – building of the feeding point I was really surprised :

cameradownload-073.jpg cameradownload-074.jpgcameradownload-075.jpgcameradownload-078.jpgcableties.jpg

Only this is for separate post ! 🙂 This showing how to make impedance matching directly whit coax ! So on this on the last picture coax line is impedance matched.

cameradownload-082.jpg cameradownload-080.jpgcameradownload-079.jpg

Next is connecting coax to the slot, second picture is fine tunning, and the third is preparing for mounting. Tunning is made by extension of the slot.

Go on the sites shown up and read the instructions for building this ones You may find thing that I missed.

9dbi Omni Rubber Duck

Friday, August 10th, 2007

Finally I was able to find info about original 9dbi omni rubber ducky antenna!

All pictures are from this site : http://www.digga.eu/wlan/9dbi/

Here it is – no surprises here 🙂

cimg0437_small.jpg

cimg0390.JPG9dbi_01.jpgcimg0406_small.jpgcimg0409_small.jpgcimg0425_small.jpg

Looks like there is no way to tune this antenna – here is the feeding point.

cimg0400_small.jpg

For more info about building this one go on site http://www.digga.eu/wlan/9dbi/

And for me was just left to see only ripped 7dbi omni antenna 🙂

Thanks to the author of the site for the pics.