How to erect the antenna

Before you buy any equipment please get in contact for a free site survey to ensure you can receive the network (see coverage)

If you're lucky, then you may be next door to another node- in which case congratulations you may not need an external antenna!

For the rest of us however, an external antenna will make your connection far more reliable and will improve the speed of your network.

Look at the node's antenna you are trying to connect to. Microwaves require direct line of sight for a decent signal, so a rooftop mounting is probably going to get the strongest reception.

Antenna installation can be arranged but this will incur a fee. Please get in contact for a quote (all depends on siting etc.)

What kind of antenna?

These come in a number of flavours:

• Omnidirectional - reasonably expensive and propagate signal in a doughnut shape around the antenna. Used to distribute signal to numerous nearby nodes. The most common type of antenna to be used on an Access Point. Depending upon gain (how well they receive/transmit) they range around 4cm in diameter and from 30cm to 100cm in length.
• Flat panel - directional and unobtrusive, good for getting connected over reasonable distances. It is a dark grey box 3cm deep and depending upon gain 12cm to 30cm across.
• Yagi- much like your TV aerial- focusses the signal in a particular direction, good to connect to nodes more than 500m away or if you can only get poor reception
• Parabolic - a bit like a satellite dish. Precise narrow focussing of the radio signal. Excellent for long distance point to point links or to improve reception. Depending upon gain these range in size from 40cm to 90cm across Most common client antenna.

What kind of antenna cable?

Choose the best quality cable you can afford to minimise signal loss. Losses arise through inaccurate antenna alignment, poor quality cable and poorly fitting connectors. Example loss:

Cable Type - dB loss/100ft
RG58 - 35
RG8 - 21.6
LMR200 - 16.5
RG213 -13.7
LMR400 -6.6
LMR600 -4.3
LMR900 -2.9
LMR1200 -2.3

Every 3dB= 1/2 of the power gone, so 2 metres of LMR 600 will lose approx 0.18dB (7% of transmitting power), whereas 2 metres of RG213 will lose approx 0.82dB (18% of transmitting power), 2 metres RG58 will lose 1.64dB (32% of transmitting power)

If there's going to be a long length of antenna cable, you might be better off buying a LocustWorld MeshAP and putting that near the antenna (again to minimise signal loss), then running some network cable to your computer. This method can also be used if you're going to mount your antenna on an outbuilding or tree by mounting the hardware in a suitable waterproof box.

Procedure

Ensure that there is a clear LOS to the transmitting antenna and that the distance is appropriate for your type of antenna (<200m:omni; 200m-1km:yagi or flat panel; >1km:parabolic)

Install antenna onto bracket and roughly point antenna towards transmitting antenna

Using signal strength monitor on Netstumbler fine tune antenna until signal is optimal. Tighten bracket

Run cable to where radio hardware is to be installed

Antenna installation can be arranged but this will incur a fee. Please get in contact for a quote (all depends on siting etc.)

Large Parabolic antenna	Dlink 900AP+ set in client mode, free standing in loft just behind antenna
Parabolic antenna in hedge	Parabolic antenna in hedge close up
Omni Directional on a barn

Last update Wednesday, March 14, 2007 2:24 PM