Point to Point Wireless Link in Kenya: Linking Buildings Without Cable

A typical call goes like this: the internet and the CCTV recorder are in the main house, and the owner wants cameras and WiFi at the gatehouse 120 metres away, or at the farm store across two fields, or at a second shop on the other side of the road. Cable is limited to 100 m, digging a trench across a driveway or a public road is expensive or simply not allowed, and a WiFi extender will not reach. A point to point wireless link, sometimes called a wireless bridge, solves this with two outdoor radios aimed at each other. Done properly, the far building behaves as if it were on the same cable as the main one.

What a point to point link is, and typical uses

Each end has a directional radio mounted outdoors. One is set as the access point, the other as the station, and together they act like an invisible Ethernet cable. At the far end you plug in whatever you need: a switch, an access point, IP cameras, a VoIP phone or a till PC. Common jobs we see in Kenya:

• Gatehouse to main house. Gate cameras, an intercom or an access control reader at the gate, recorded on the NVR in the house.
• Farm stores and staff quarters. Cameras on a store or dairy shed hundreds of metres from the farmhouse, where trenching is impractical.
• A second shop or office across the road. Sharing one internet line and one CCTV system between two premises.
• CCTV backhaul. Bringing camera feeds from a remote yard, parking or warehouse back to a central recorder.
• Estates. Linking a guard house to a management office or a second block. Our guide on access control for apartments and estates covers what usually sits at the gate end.

If the far building is under 100 m away and you can run cable safely, cable is still the better answer. See our Cat6 cable price guide for outdoor options.

Line of sight and the Fresnel zone, in plain terms

The two radios must see each other. Not roughly, not through a mango tree, but a clear view from one dish to the other. 5 GHz signals are absorbed by leaves, walls and water tanks, and a link that works in the dry season can drop out when the trees fill in after the long rains.

Clear line of sight is necessary but not quite enough. The radio signal travels in a fat, rugby-ball shaped zone between the two dishes, called the Fresnel zone. It is widest at the middle of the link. If a roof, wall, tree or the ground pokes into that zone, the signal weakens even when you can see the far dish with your eyes. The usual rule is to keep at least 60% of the zone clear at the midpoint.

The radius at the midpoint is roughly 8.66 × √(distance in km ÷ frequency in GHz), in metres:

In practice this means: mount both radios high enough that the straight line between them clears roofs, boundary walls and tree tops by at least those margins in the middle. On a flat farm, that often means a mast at each end rather than a bracket on the eaves. On a long link the curve of the earth also starts to matter, which is another reason longer links need taller masts.

Choosing the radios: 5 GHz vs 2.4 GHz and our Ubiquiti options

For a dedicated link between buildings, 5 GHz is the normal choice. It has many more channels than 2.4 GHz, and the 2.4 GHz band in Nairobi and most towns is crowded with home routers, phones and hotspots. 2.4 GHz copes slightly better with partial obstruction, but it is slower and noisier. Use it only for short, simple links where its lower price matters more than speed.

You need two radios for one link, one at each end. Prices below are per unit, with the pair price beside it.

How far will they go? With clear line of sight, the 5 GHz airMAX radios can reach up to several kilometres, depending on model, interference and how well they are aligned. The PowerBeam's larger dish gives a stronger, more focused signal than the LiteBeam, so it holds up better on long links and in areas full of other 5 GHz equipment. For a gatehouse 100 to 300 metres away, a LiteBeam pair is normally plenty. We would rather size the link to your actual site than quote a headline range figure, so send us the distance and a photo from each end.

CCTV over a wireless link

CCTV is the most demanding thing most people put over a bridge, because cameras stream all day. Add up the bitrates: eight 2MP cameras on H.265 at about 2 to 4 Mbps each need roughly 16 to 32 Mbps continuously. A well-aligned 5 GHz airMAX ac link normally has plenty of headroom for that. A 2.4 GHz M2 link is much more limited; keep it to a few cameras or to sharing internet.

Two ways to set it up:

1. Cameras at the far end, recorder at the main house. The link carries every camera stream. Simple, and all footage is in one place. Plan the link for the full camera load.
2. A small recorder at the far end. The link only carries what you view live or play back. Recording continues if the link drops, which is useful on long or exposed links.

At the far end, a small PoE switch powers the cameras from the same link. Our CCTV hard disk calculator shows the bitrate maths in more detail.

Mounting, power and cabling

• Mount solidly. Use a galvanised pole or mast clamped to a wall or roof structure, not a bracket screwed into the fascia board. Wind moves a loose dish enough to drop the signal.
• Power over Ethernet. These airMAX radios use 24 V passive PoE and normally come with an injector in the box; confirm when you order. Do not assume a standard 802.3af/at PoE switch port will power them. The injector sits indoors and one cable runs up to the radio.
• Use outdoor cable. The run from the injector to the radio is outside, so use an outdoor LDPE jacket such as the Giganet Cat6A outdoor LDPE drum (KSh 26,000). Leave a drip loop below the radio so rain runs off rather than into the port.
• Earthing. A mast on a roof is the highest metal point around. Earth the mast and, ideally, use shielded cable and connectors, with a surge protector where the cable enters the building.
• Keep it running through KPLC outages. Put the injector, router and switch at both ends on a UPS. A small 650VA UPS (KSh 8,000) usually covers a radio, a switch and a router for a short outage.

Aligning the link and setting up the network

1. Configure both radios on a bench first, side by side: one as access point, one as station, the same SSID and security key, and a fixed management IP on each. Make sure they link before you climb a ladder.
2. Mount both and point them roughly at each other, using a landmark or a compass bearing from a map.
3. Use the signal meter in the airOS interface (on a phone or laptop at one end) and move one dish slowly left and right, then up and down, until the signal is strongest. Tighten it, then repeat at the other end.
4. As a rough guide, a signal somewhere around -50 to -65 dBm is a healthy short link. Very strong readings on a short link can mean you should turn the transmit power down.
5. Run a speed test across the link and leave it for a day, including an evening and a rainy spell if you can, before you hand it over.

For the network itself, a router at the main site keeps things tidy. The MikroTik hEX RB750Gr3 (KSh 9,500) suits a home or small business. On MikroTik you can keep CCTV and office traffic on separate networks so cameras are not reachable from guest WiFi.

If the far end needs WiFi coverage across a yard, compound or farm, plug an outdoor access point into the link. The Ruijie RAP6262(G) WiFi 6 outdoor access point (KSh 19,000) is built for that; check its datasheet for the PoE power it needs. Do not try to use the bridge radios themselves to give phones WiFi.

Send us the distance, a photo from each end looking towards the other, and what you want at the far end, on WhatsApp at +254 718 811 661 or via our contact page. We install in Nairobi and deliver radios anywhere in Kenya for a flat KSh 300 with cash on delivery. More gear is in networking and WiFi.