Communications, Radar & Electronic Warfare (201.. - Index of

Radio-Controlled Improvised Explosive Devices 139transmitter used to trigger the RCIED must also be within range of the receiver. Thiswill depend on a number of factors, as explained below.The key radio parameters are:• frequency of operation;• transmitted power;• transmit and receive antenna heights;• antenna gain/loss;• noise floor at the receiver;• sensitivity of receiver device.Because of the topology of the scenario, it is likely that the transmitter and devicereceiver will be within a few hundred metres of each other. The exception to this can bewhere existing networks are used, such as GSM mobile phone systems. In this case, thebase station used to relay the trigger command may be many kilometres away.Since the range is typically so small, it is possible to identify the critical factors thatwill affect performance of the radio link.• Terrain effects will not normally vary significantly within the operational range,although of course there are exceptions to this.• Atmospheric variations will in general be negligible.• Local clutter such as buildings or dense vegetation may be the dominant attenuationfactor.• Ground conductivity may be an important factor within this regime, since theantennas will typically be so low above local ground (less than one metrehigh typically).• Local fading will be an important factor within the nominal coverage range.In terms of radio prediction and simulation, it is usually not possible to determinewhere precisely an attack may occur and therefore from a device inhibition (i.e.jamming) point of view, a site-general model approach is necessary. US forcesadopted a simple model with a correction for ground conductivity. This is used torepresent both target and jammer links. The model is shown below. It assumes that thejammer is for VHF communications links only, that the effective Jammer to SignalRatio (JSR) is approximately 8: 1 (linear terms) and that the links have no or minimalintervening terrain.The model provides two formulae, the first one to determine the necessaryJammmg power: