WLAN
Working with a power splitter

A power splitter (aka 3dB combiner, power divider etc.) is used to combine two, three or four antennas on one antenna connector.

Such a combination of antennas makes sense, if
- a higher gain is required;
- a larger area or different directions have to be covered;
- setting up an omni directional radiator with strong downtilt.

Power Splitter now also available for 5GHz, useable on the entire band from 5 to 6GHz. Available with connections for 2, 3 or 4 antennas, all connectors N female.

Combining for more gain

Radio amateurs often combine several antennas in the same direction to achieve a higher system gain. With WiFi this is usually not required because the available antennas offer suffcient gain to reach the legal limit.
To use such a combination in the same direction the antennas must be fed with phase aligned signals, i.e. all signals must be in exactly the same phase. This is achieved by using cables of precisely the same length between splitter and each antenna. The absolute length is not critical, just that all cables are of same length.
Each time you double the antenna number the gain rises about +2dB. The stacking distance of antennas is critical and should be calculated or looked up in the appropiate literature.

Combining for several directions

If a larger area or different direction should be covered by the signal, one can use two, three or four antennas and combine them with a splitter. The antennas are pointing in different directions, e.g. two sector antennas with 70° each can be combined to cover a sector of 140°.
The distance of antennas is less critical. The length of the cables feeding the antennas is only critical if the antenna segments overlap, if so the cables should be of same length.

Combining for a larger omni-directional antenna

Often splitters are used to combine three (3 x 120°) or four (4 x 90°) sector antennas into one omni-directional antenna. The benefit over a traditional omni antenna is that each individual antenna can be down tilted to the required degree, giving better coverage at the close vicinity of the antenna base.

Power distribution with a splitter

When using a splitter one has to consider the effect that the transmit power is divided equally between the antennas. I.e. with a 2-way combiner each antenna only receives 50% of the total power, with 3-way splitters about 33%, with 4-way splitters 25%. This relates to -3dB, -4.5dB or -6dB respectively, so you can use larger antennas before reaching the legal limit.
The received energy is combined and fed to the common connector of the splitter. This works usually without problems, unless the antenna segments overlap. In this case the antennas should be connected by cables of exactly the same lengths.
Of course a splitter introduces some insertion loss, but these are about 0.2 to 0.5 dB and therefore negligible.

Note: if you use a power splitter and leave some ports open, these ports must be terminated with a 50Ω coax resistor. Our product 21023 is a suitable terminator for that.

Example with two antennas

	Take two antennas... It is not necessary to use two antennas of the same type, you can mix different models. For better channel separation you can use different polarisations, e.g. one antenna vertically, the other horizontally polarized.
	Seen from the rear for better visibility...
	Add a 2-way power splitter 18096...
	Connect the first antenna with a short low loss cable to the splitter. Which of the two upper connectors is used doesn't matter.
	Likewise connect the second antenna. It makes sense to lay the cables in the manner shown in the picture. Due to the cable going below the connector of the splitter, rain water can gather at the lowest point, alleviating excessive moisture at the connector.
	A third cable from the common connector of the splitter connects to the WiFi equipment, probably using a lightning protector.
	Mount everything to a pole... Fix cables and splitter with weather and UV resistant tie wraps (click on picture for larger view (150KB)). After the final installation you should protect all connectors with self sealing, self adhesive tape (WiMo product 23065).

Splitter 2.4GHz WLAN