Instrumentation

Engineering

Limited

RF Detectors
Description

Operating Instructions

To switch the unit on push the power circle on the polycarbonate panel. The unit will then display the battery level for approximately four seconds on the LED display. While in the battery check mode the yellow LED weakly illuminates to show this mode.

After the four seconds the unit then displays the detected RF level on the LED display as a bar graph. The unit will continue to operate for approximately 45 seconds and then power down. If the power button is again pushed within three seconds the unit will skip the battery check and go to RF level mode immediately. To stop the unit powering down the user may continue to hold down the pushbutton for as long as desired, or push the button before the 45 second period ends.

The Audio tone generated form the module is modulated by the intensity of the RF level being detected. The tone is active from switch on, even while the display is in battery monitoring mode. The volume of the tone can be set via a 16 position switch on the back panel. It can be adjusted with a small philips screwdriver through the access hole provided.

To track down a source of electromagnetic radiation some practice with the unit is required. This can be accomplished many ways but here are two that we have found to work very well.

  1. If a microwave oven is available put a large container of water in the oven and set it going. The ERD detector is more than sensitive enough to detect the microwave leakage (2400MHz) from the oven. In No circumstances put the unit in the oven. Practice moving toward and away from the Microwave oven while it is going. It will be found that as the distance from the oven doubles the LED display falls by one LED. Halving the distance to the oven will conversely increase the level on the LED display by one LED.
  2. Set up a Cell phone call to another party, while the phone call is up the unit can be used to detect the radio frequency energy emitted from the phone. As in the above test, the LED display on the EMR detector will go up one LED if the distance to the phone is halved and down one LED if the distance is doubled.

The above distances and LED position are approximate due to the vagaries of electromagnetic wave propagation. Electromagnetic propagation is affected by metallic objects that cause reflections of the waves which can reinforce or cancel the wave energy.

In Urban areas it is normal that the unit may display 1 or 2 LED’s on its display. This is because of sources such as cellular base stations, television and radio transmitters somewhere in the neighborhood.

The sound of the tone from the unit and the number of LEDS lit on the panel can give some idea of the sort of electromagnetic source you are detecting. Microwave ovens and digital cell phones have an unpleasant tone and the LED display has many flickering LEDs. Linear electromagnetic sources have a more pure tone and less flickering on the LED display, these sources include FM broadcast stations and simple bugging devices. Cell phones typically use higher power levels when establishing calls and drop to a lower power level once the call is established. Practice with the available types of phones in your area will soon enable the user to detect which type and its whereabouts.

Remember the ERD, when held normally, is more sensitive to horizontally polarized radiation holding the unit at 45 degrees will make it equally sensitive to horizontal and vertical radiation so some movement of the unit to maximise the display reading may be required.

When not in use for several days or more the battery in the unit should be disconnected and if use is not foreseen for longer periods the battery should be removed from the unit altogether to mitigate the effects of battery leakage damaging the internal printed circuit board.

RF Detection

The ERD is protected by a Patent NZ 518497. No other unit on the market has the dynamic range and frequency range offered by this unit. This graph is compiled from data from an Australian type approval Laboratory where in RF anechoic conditions the ERD was measured for sensitivity to Radio Frequency Radiation. Also included on the graph is the old UK exposure limit for the general public over a four hour period so that users can get some idea of what may be considered hazardous.

Note: IEL - the designers and makers of this instrument consider that any field level over LED 8 (the last green Led) and higher should be considered possibly harmful and exposure time to such fields kept to a minimum.
©2008 IEL