Posts Tagged ‘wlan’

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 : and

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.

Slot Length
2.15 l
Slot Width
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


Here is some pictures from


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.

wlan splitters more …

Saturday, August 4th, 2007

I was thinking about this one :

“… The doubling of the output power is equivalent to a 3 dB increase in the signal. If the combiner is 90% efficient then a 2.5 dB gain is seen. Note the dichotomy:

· If the antennas point in different directions, there is a 3.5 dB loss at the combiner.

· If the antennas point in the same direction, there is a 2.5 dB gain at the combiner.

(This is a 6 dB swing. 3 dB of this is just the adding of the second antenna, but the other 3 dB is from the combiner becoming a much more effective device.) … ”

If someone understand this and have any info Please send me a link, or tell me what to look for.

D-Link ANT24-1800 18dbi wlan antenna

Wednesday, July 25th, 2007

Some NEW info is available about this antenna new pictures here.

This one look interesting so here some info about it.

Most of the info came from these sites :

So no doubt that russians show this antenna to the world – Thanks !

More antenna specifications

Input : 50 ом

Frequency range : 2.4 -2.5Ghz

Gain : 18 dBi

Polarization : Linear, vertical

VSWR 1,5 max

Diagram : horizontal – 15° vertical- 15°Dimensions : 360 x 360 x 16mm

D-Link ANT24-1800 18dbi wlan antenna

More pics can be found in the upper sites.

Drawings from elk again d-link 1800.rar but on You can find another two files which may be the same – I’m not shure.

Dimension between pcb plate and reflector is 9mm.

I’m not sure but, this antenna will be hard to reproduce because we do not have info about thickness of substrate nor dielectric constant of the material. So this is not a option to build and test for me right now.