WiFi Sector Antenna How to Tutorial
WiFi Sector Antenna How to Tutorial
On this page you will find information on how Pe2eR builds a sector antenna for de Wifi 2,4GHz ISM band.
The design was published by Dragoslav Dobričić, YU1AW.
Most of his work is in Serbian, but Dragoslav and Pe2eR have corresponded in English. they differ a little about the dimensions of Dragoslav AMOS antenna. When Pe2eR build the antenna as Dragoslav describes, it usually has best VSWR below the Wifi band, so Pe2eR shortened it a little.
So now this antenna is suitable for use in Computer Radio LANs conforming to the IEEE 802.11b/g standard – better known as Wifi. It can be used on an a La fonera Router or Wifi client with equal benefits.
The properties
Frequency: 2,4 to 2,5GHz
Impedance: 50 Ohm @ 2,45GHz
VSWR: < 1:1,5
Polarisatie: Verticaal
Gain: 11dBi
Vertical beamwidth: (-3dB) 15º
Horizontal beamwidth: (-3dB) 125º
Connector: Female-N type (50 Ohm)
Principe
The antenna is a centre-fed broadside array antenna, based on the Franklin Antenna as published in Rothammels Antennebuch (shown below)
Building the antenna step-by-step.
Make a hardcopy of the Autocad drawing (the antenna is drawn to scale 1:1).
Use 292.2mm of approximately 1.8mm diameter copper wire for each radiator. Stretch wire (to straighten it). This wire is commonly used in Dutch house wiring. Put the wire along the linear scale on the drawing and mark it as shown (I use a permanent CD-ROM marker)
Next, prepare 4 pieces of PE studs. Use the insulator from RG-213 – like cable. Each stud is 15mm long. Drill a 2mm hole 10mm from the end.
For the reflector, use 495x62mm of Copper-clad circuit board. Copper side must be on the same side as the radiator (Pe2eR used double-sided PCB).
Drill a hole in the center to accept your N-Type connector. Pe2eR used one that comes with rigid coax attached. The shield of the coax should extend to 28mm above the surface of the PCB. The centre conductor must extend 5mm more. Drill 4 holes to attach the studs to the reflector.
Bend the two radiators. Do not forget to slide on the PE studs before bending. Remember: It is the amount of wire you use that is important, not the final dimensions after bending!
Fabricate the 1:4 BALUN from ½ wavelength of coax (measured by the shielding).
RG-316 (v=0,697): 43mm (This is the coax cable I use here)
RG-58 (v=0,66): 40,7mm
CFD200 (v=0,83): 51mm
“Verbindingen KORT houden” means “keep connections SHORT as possible”.
Solder the radiator to the coax feed/ BALUN.
used S-Lon 65mm mini PVC rain gutter to house the sector antenna. Pe2eR is sure that this is not available all over the world, so you need to find something similar.
continued...!!
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