High-speed near-field search receiver NS-13-081 is designed for the instant detection of radio transmitting overhearing devices - wireless microphones, telephone retransmitters, radio stethoscopes, etc. The device also provides detection and recognition of DAMPS, GSM 900, GSM 1800 cellular standards, as well as DECT and Bluetooth signals.
Owing to the availability of passive acoustic correlator, NS-13-081 can secretly and silently detect the sources of RF radiation without the aid of an operator.
The receiver has two operation modes: the search mode to detect and locate sources of radio signals and the alarm mode for permanent radio monitoring in a real time. The NS-13-081 device can detect frequencies in the range of 20 through 3000 MHz.
Upon detecting a signal, the receiver displays its frequency and level. The demodulated signal can be listened to through the built-in loudspeaker or headphones.
NS-13-081 can detect radio transmitters with a power of 5 mW at the antenna within a distance which is not less than 5 m. Duration of scan cycle depends on the environment interference and averages several seconds per the whole frequency range.
A method of correlation used in the receiver is designed to detect radio transmitting eavesdropping devices and based on comparing the demodulated signal with the reference acoustic signal, which presents on the premises.
The algorithm used in the NS-13-081 is based on the computation of cross-correlative function of the current power of acoustic signal, i.e. on the computation of its envelope. Due to this fact it is not necessary to take into account a difference of forms of the investigated and the reference signal, which is caused by the resonance properties of the premises. This greatly enhances the reliability of the analysis. For realization of this algorithm a voice signal is the most suitable, because it has a high peak factor (i.e. current power change). In addition this method lets detect radio transmitters with a secure analogous channel, for example with a spectrum inversion.
Distinctive features:
- built-in acoustic passive correlator;
- alarm and search operation modes;
- RS-232 interface for connection to PC.
