Counter surveillance, Bug hunters Probably the most commonly and widely used of all the surveillance devices is the RF transmitter bug. At the lower end of the scale you will find the free oscillating VHF transmitter, transmitting on the commercial FM band 88-108 MHZ or the VHF airband 108-140MHZ. These devices are inexpensive easy to use and require no specialised receiving equipment. Due to their low cost, there is very little incentive to recover these once planted. This is the type of bug most often used by private investigators and individuals, and the chance of finding the person who plants it, is low. Moving further up the scale and very similar in operation is the crystal controlled VHF or UHF transmitter. These devices tend to operate slightly higher up the frequency band than the free oscillating transmitter and are tuned to a fixed frequency. These require a dedicated receiver, or if you prefer a narrow band scanner may be used, the advantages are greater stability and less chance of casual interception of the signal.

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