Radio Frequency Sniffer : Design Review by Liem Nguyen 1

Problem statement Radio frequency: good and bad Bad – Unwanted radio freq. during device testing/ medical zones – i.e Cell phones in WAT 322 – RF interference with medical devices – “Spying”/ eavesdropping Solution – 1.8 GHz RF detector (i.e cell phone) 2

Methods: Block Diagram Figure 1: Block Diagram of RF receiver used in Sniffer Circuit. 3

Methods: Circuit Original Schematics Courtesy: Kainka B. [1], Varner G. [2] Figure 2: Directional RF Sniffer circuit with speaker output. 4

Methods: Specs Dual λ/2 Dipole antennae at 90° – Target frequency = 1.8 Ghz – Dipole arm length : λ/4 LM358 – High gain Speaker output – Adjust gain with 1M-ohm Linear Pots Figure 3 [3]: LM358 pin layout 5

Summary Antenna - Dipole arm lengths ~ 3cm Circuit layout 75% Complete -Missing Schottky diodes, Speaker + Driver Further improvements - Calibration with known rf source -Tune Inductance loading 6

Timeline Dec. 12, 2013 Build Dipole antenna Observe signals on scope Dec. 16, 2013 Final Calibration Solder to permanent board Dec. 17, 2013 Final Presentation Dec , 2013 Refine antenna length Build and test w/ speakers Gather final materials 7

References [1] Kainka, B. (2002). “Mobile Phone Sniffer” Elektor Electronics. Pp Web. 21 November, [2] Varner, G. (2013) Physics 475 Website. [3] Texas Instruments Website: LM358 Op Amp Available [Online]: 8

Questions?? 9