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s . 10/ 19/83 3910.3A (2) The antenna deck of the radar tower shall be considered a restricted area. Interlocks on antenna deck access gates shall not be defeated while the radar is transmitting without permission and without careful consideration of the purpose. This does not mean that entry to the antenna deck will result in overexposure to RF radiation, but that in this area the RF energy is neither a clearly defined field nor is it confined as it is in other parts of the system. Consequently, extra precautions are necessary to minimize exposure. (3) Where sector blanking is used to prevent transmission in certain azimuths and/or elevations, and overriding will cause a RF hazard potential in an adjoining workplace, sufficient warning shall be provided to personnel in the workplace so that proper precautions may be initiated. (4) RF generators, waveguide joints, waveguide switches, rotary joints, etc. , that are potential sources of RF radiation leaks should be surveyed routinely and also whenever it is suspected that maintenance or operational changes have altered the radiation hazard potential. 37. VORTAC's and TACAN's. a. Hazards. VOR's transmit in the frequency range of 108 to 118 MHz. From Figure 3-1, the PEL is 1.0 mW/cm2 power density (E2 = 4,000 V2/m2; H2 = 0.025 A2/m2). In a survey of a VOR transmitting at 110.2 MHz (TACAN off) and 200 W, a mean squared E field strength of approximately 4624 V2/m2 was measured at the surface of the conical tower covering the rotating antenna. At the outer edge of the building roof the level was only 324V2/m2 so it was concluded that a potential hazard existed at the surface of the conical tower only. TACAN's transmit in either of two frequency bands, 962 to 1024 MHz or 1151 to 1213 MHz. The PEL is defined in Figure 3-1 as f/300 mW/cm2 power density (E2 = 4,000 f/300 V2/m2; H2 = 0.025 f/300 A2/m2). In a survey of a typical TACAN operating at 6.5 kW peak power (130 W average power) and a frequency of 983 MHz, a mean squared E field strength of 13,924 V2/m2 was measured at a distance of 5 cm from the surface of the radome; at 20 cm the level was 11,664 V2/m2. Since the PEL for a 983 MHz source is 13, 107 V2/m2 , it was concluded that a potential hazard existed at the surface of the radome only. b. Procedural Controls. (1) Personnel should avoid direct contact with the surface of the VOR conical tower and, to avoid unnecessary exposure to low level RF energy, they should limit their occupancy of the counterpoise while the VOR is transmitting. Chap 3 Par 36 Page 31