The active system consists of 2 key elements that must both be set up correctly, the Loop Cable and the 2.4GHz antenna for receiving data.

Loop Cable Set up

In most cases, the cable loop will be laid on the ground and either taped down with duct tape or covered by a mat.

The loop cable should form a rectangle with a width of between 30cm and 60cm, with the exact line on which you wish to record a time positioned across the middle of the length of the loop.

Where possible use a loop of exactly the required length, at all times avoid coiling any excess loop cable since this can cause interference resulting in transponders not being activated. Loop cables cannot be installed on metal surfaces, these will completely inhibit the loop signal meaning no passings will be generated. 

Loops can be buried in the ground, particularly for motorsports or on soft surfaces, when doing so it is common practice to protect the loop using some sort of pipe. 

Loop Width

If you require higher precision, the loop should be narrower, and greater care must be taken to set up the loop precisely. Note that 0.01 second means only 5cm distance at 70km/h. So aligning the loop a few centimeters askew will have a negative effect on precision.

A wider loop, on the other hand, will result in higher read height but may lower precision. This is usually the preferred setup since most sports requiring the greatest precision require a PhotoFinish camera for verification. 

In general, you should only make your loop narrower if you are confident that all transponders will be mounted at the same height (below 100cm or 50cm for MotorKart) and the maximum speed is also below 100km/h, this should also then be complemented by a lower Loop Power to maximise precision. 

You can see some guidelines for loop width / loop power and the resulting max detection height here

2.4GHz Antenna

The 2.4GHz antenna is used to communicate with the transponder, this is how the system receives the exact passing time from the transponder. It is critical that there is a clear line-of-sight between transponders and the 2.4GHz antenna, and the antenna must be used at all times. 

In the event that the Active Extension has an obscured view of transponders then it may be necessary to use an  Active Range Extender, this is a higher gain antenna, fitted to a longer cable allowing the antenna to be mounted higher and away from interference.

Note that the additional gain of the antenna is lost in the length of the cable and so simply setting up the range extender on the ground in the same position will have no additional benefit. 

Antennas should be mounted pointing vertically upwards and kept away from metal as much as possible since this can interfere with the signal.