BALDOCK - Monitoring Facilities

The EMC mobile facility and its equipment

Two mobile laboratories are able to carry out a diverse range of work, as basic as the timing and level measurement of a humble boiler thermostat to as complex a matter as the measurement of spurious radiation from the most sophisticated radar system.

One vehicle is equipped with 10m and 28m pneumatic masts, a 4 kVA generator and equipment for measuring environmental conditions.

The second vehicle is larger and has a roof mounted azimuth/elevation positioner. This vehicle provides the platform for precise in-situ measurements at SHF and more space for longer-term tasks.

Both mobile laboratories are capable of receiving and measuring signals from 9 kHz to 110 GHz although the bulk of the work is performed between 9 kHz and 40 GHz.

At present most EMC Standards call for measurements between 9 kHz and 1 GHz. As more research, planning and assignments are being undertaken in the microwave spectrum the higher frequency capability of the mobile laboratories will come into play.

High quality measuring receivers can be programmed with antenna factor values and cable losses thus allowing incoming signals to be displayed directly as units of field strength.

The available equipment, together with the broad experience of the staff, presents mobile interference and EMC measurements to be made within the frequency range 9 kHz to 110 GHz.

Measuring

Receivers can be operated manually or automatically. The automatic process gives receivers a spectrum analysis facility allowing visual RF/IF scans to be displayed. These can be stored electronically or plotted for compiling reports.

These units also allow automatic EMC testing to be carried out and standard level limit lines to be displayed over a displayed emissions profile, giving a ready indication of over limit emissions.

To cover the microwave spectrum an EMC interference-measuring receiver is available which covers 1 GHz to 18 GHz. By use of a frequency extender unit the receiver range is increased to 40 GHz. The extender unit can be mast mounted with the appropriate horn antenna fitted directly to its case. When used in this fashion the incoming signals are converted to an intermediate frequency of 250 MHz allowing the use of conventional coax for the mast down lead to the main receiver.

The EMC microwave receiver can be coupled, via an IEEE 488 interface, to a laptop computer, and by using appropriate software the receiver converts to a sophisticated spectrum analyser allowing automated measurement runs and in-depth signal analysis to be made. The results of spectrum scans can be saved and plotted for later inclusion in reports. In addition to the receivers, the mobile laboratories are also equipped with a spectrum analyser covering the 0 to 50 GHz range.

The mobile laboratories also have portable receivers that are mainly used for on site source identification and for field mapping by using the additional GPS (Global Position System) receiver and a laptop computer.

The system can also be used for long term unattended monitoring of the VHF and UHF bands.

Field strength mapping systems

The field mapping systems are used in the mobile laboratories support vehicles and allow transmitter field strength profiles to be annotated directly onto a mapped route of the area of interest. These systems not only allow the mapping of transmitter field strength profiles, but also give positive indication that a station's output has changed since initial mapping.

The method of profile mapping has many advantages over manual techniques. It is fast, as the measuring vehicle can travel at normal traffic speeds, and many hundreds of individual measurements can be taken per km.

Other equipment

To supplement receiver capabilities the mobile laboratories also have frequency generating facilities from 100 kHz to over 40 GHz.

These units are used for equipment confidence testing, cable testing, cable calibration, RF field generations and spectrum marking. In addition, the generators can be used to drive a series of broad band linear power amplifiers. These cover the range 1 MHz to 1 GHz and when used in conjunction with suitable antenna can check equipment susceptibility problems.

The mobile laboratories also carry comprehensive antenna sets. These have the option of being mast mounted on the vehicle or tripod mounted remotely from the vehicle.

Quality assurance

The Station's Quality Manager overseas the work of the EMC laboratories and ensures that all measurements are carried out according to procedures laid down in the UKAS Quality Manual.

The Section has access to detailed RF propagation modelling software that can identify ideal monitoring sites and be used to give a full coverage prediction support by the field mapping system.

For further details of all sections of the station, please contact:

Tel: 01462 428500

Fax: 01462 428510