Recommendations for Operation of Selective Frequency Meter SEL SP-71R Raksa


So if you thought about detection of eavesdropping devices, or for that there is already a reason, or you are a careful person and you have information that you value. In any case, you are on a right path- don‘t sit around. We hope that using our equipment the task will be solved. One of the distinctive features of this equipment is - the combination of high performance and maximum "proximity" to the end user. That is the professional equipment, which can be handled by a professional,observing some conditions and recommendations.

The detection of radio transmitters, using selective indicator SEL SP-71R “Raksa“.

It is recommended to proceed in two stages:

- search

- protection.

Search mode is used when you want to know, if there a covertly installed eavesdropping device present in the premise or a wireless video cameras and so on.

At this point the active radio transmitters are present. Next step is to determine their placement Please note that during the search the room should be free of sources of radio sources – to check  if anyone‘s using a cellular or a cordless phone, Bluetooth, Wi-Fi, domestic microwave ovens. Another important condition: to activate radio transmitters that are being activated by sound ( those that activate when there is a sound in the room) is necessary to ensure the presence of an acoustic signal such as that from a radio receiver when the volume should be sufficient to activate them.

Radio transmitter detection requires two complimentary steps – search and guard. Search Mode enables to detect and locate the transmitters activated to the moment. Guard Mode provides continuous monitoring of the radio signals thus the transmitters are detected at the moment of their activation.

Before searching the target area all the radio signal sources should be switched off (mobile and cordless telephones, Bluetooth, Wi-Fi, microwave ovens). To activate the transmitters with voice control use any sound source.

Place the RF detector in the centre of the room and switch on Search mode. Gradually approach the probable transmitter locations and watch the possible change of the signal level. Both light and sound indication can be used – the closer to the source of signal – the higher is the frequency of flashes. The high flash increase might indicate a hidden surveillance device.

After verification of the clean area change the mode to Guard and place RF Detector at your convenience. The RF Detector should stay stable to avoid false alarms. The alarm signal is generated when detection a threat radio signal.

The efficiency of radio signal detection in Guard Mode depends on correct setting of threshold levels. The mobile phones for instance are characterized by wide range of signal magnitude. Use the Digital Signals Monitoring Mode to define the signal levels of mobile and cordless phones, Bluetooth and the like and adjust the threshold level if necessary. The higher is the threshold level the less probable is false alarm but distance of detection will lessen as well.

Once again we would like to underline, that with help of this device you will detect only active (working) devices. Those that are not used anymore can be detected using a more sophisticated devices (f.e. non linear junction detectors) or with detailed physical inspection

Follow the changes of level that appears on the display. It is convenient to use light and sound indication of signal strength – when approaching the source of radio frequency led flashes and an acoustic signal increases. Sharp increase in the level in a certain place means the presence of a radio transmitter.

An additional criterion of the signal from the wireless microphone is called acoustic feedback. Turn on the listening (audio mode) - appears a characteristic whistling noise when you move the indicator to the height of its tone is changed.

To increase the guarantee of a search result, It is recommended to carefully pass the indicator through all the items of furniture and interior at a minimum distance from their entire surface - 20 - 50 cm.

After being considering and making sure that there are no active eavesdropping devices, switch the indicator into Guard mode and place it to the place most appropriate for you.

At the stage of monitoring, a continuous over watch over radio signals, therefore the radio transmitters are detected at the moment of their activation.

This mode is recommended to use during meetings, negotiations, visiting places, where you are on “foreign territory”. In this case the indicator can easily lay in the pocket. The built in antenna enable operation even there.

Besides, this mode will help you when a guest in your own office, left you a “surprise”.

In monitoring mode, please refrain from moving the device around, it may create false alarms. In case of dangerous signal appearance, the alarm signal goes off. The sound signal in this case can be switched off, a more appropriate in this case would be soundless vibration notification.

The efficiency of detecting radio signals in this mode is dependent on proper installation threshold levels. This particularly applies to cell phones, for which the radiated power may vary within wide limits and depends e.g. on the distance between the base station and from many other factors. Use the monitor mode of the digital signals to determine the characteristic signal levels from cellular and cordless phones, Bluetooth devices, etc.

If necessary, adjust the relevant thresholds. The easiest way to do this is to turn the phone (GSM standard), place it within a distance of 2-3 m from the display and talk on this phone. The display shows the signal level. The threshold value can be set the same or a little less.

As for the other threshold signals, we recommend that you leave them default (menu item "reset settings"). Generally speaking, increasing the threshold decreases the probability of false alarms, but reduces the detection range of some sources of radio signal.

If necessary, you can disable their detection. For example, if the room has Wi-Fi, this type of alarm should be disabled to avoid the constant positives.

All the detected signals will be stored in to the log.

Work in Search mode is recommended to be performed regularly. The rest of the device can "live", without attracting attention, without requiring recharging up to 12 hours.

In this article we mentioned only those modes of the device, which are necessary for the beginner-level user.

SEL SP-71R Raksa


Silutes pl. 2 (Office No 525, 5th floor),
Klaipeda 91111, Lithuania
Phone: +370 655 08288, +370 655 08286
Fax: +370 46 411353