X hits on this document

198 views

0 shares

0 downloads

0 comments

14 / 70

realize that the measured levels are peak levels, and time-averaging must also be considered when evaluating exposure. With respect to the 1982 ANSI guidelines (ANSI C95.1-1982), there was only one instance where a maximum level exceeded the recommended exposure limits (a vehicle-mounted quarter-wave whip antenna). More details on these measurement data are given in Appendix A, where descriptions of each station and the corresponding measurement results are discussed.

Table 3 lists examples of maximum magnetic field strength measured in areas near amateur installations considered to be publicly accessible. When compared to the exposure guidelines, there was only one instance where a maximum level exceeded exposure limits. This occurred near a vehicle-mounted, quarter-wave, whip antenna at Station D that also exceeded the electric field strength limit. As with the previous table, these measurements reflect peak readings, and when time-averaging is considered compliance with exposure guidelines would be expected.

Table 4 gives examples of measurements made at "ham shacks" where amateur operators are normally located when their stations are transmitting. In general, levels encountered at these locations were well below exposure limits recommended by either the 1982 ANSI guidelines or the new ANSI/IEEE guidelines for "controlled environments." Only with the vehicle-mounted, quarter-wave whip antenna did the RF levels approach exposure limits. As before, these readings were the maximum readings that could be obtained in the ham shacks.

Table 4 also shows readings of 60-hertz magnetic fields at operator locations. These measurements were made because the EPA has become interested in investigating whether exposures to these fields might be a potential health risk. The maximum 60-Hz readings obtained during transmission ranged from 0.1 to 12.5 milligauss (mG), with most readings being less than 4 mG. Guidelines for 60-Hz exposures have not been established.

Details of the results obtained in this study are given in Appendix A. A description is provided for each of the nine amateur stations visited (designated as Stations A, B, C, D, E, F, G, H and I), and results of measurements made at each station are tabulated.

In this study, measurement results were obtained both in areas considered to be publicly accessible and in "ham shacks" where operators are located during transmissions. Frequencies chosen for use in this study were those typically used by many amateur operators. Transmitter power levels were those normally used by the operator for the system being studied, although higher levels were used in some instances for "worst case" analysis. The use of power levels up to the allowed maximum of 1500 watts (PEP) could result in higher field values in some cases.

Amateur radio facilities can generate electric and magnetic fields near antennas and transmitting equipment that, in some cases, might approach or exceed recommended limits for human exposure. For most of the stations surveyed, RF protection guidelines for field strength and power density were not exceeded in

5

Document info
Document views198
Page views198
Page last viewedFri Dec 09 22:14:45 UTC 2016
Pages70
Paragraphs2883
Words17115

Comments