The paper aims to analyze the electromagnetic field components in the near field of a high frequency (HF) emission antenna. The typical case of a dipole antenna emitting Near Vertical Incident Skywave (NVIS) HF signals at two emitting frequencies (3.6 MHz and 7.1 MHz) and at 100 W input power is being discussed. The measurements have highlighted the places around the antenna where the field levels are high, from the perspective of safe exposure to electromagnetic radiation. Thus, it was found that on a line situated just beneath and parallel to the emitting antenna, the electric field strength may exceed the safety limit recommended for the population by ICNIRP guidelines. The magnetic field component however was lower than the limit in all considered cases.
High frequency data transmission over short distances (few tens-few hundreds of km) is a valuable option for communication links in special/critical situations. Present experimental study of noise level and channel availability for digital multi-carrier modulated signals in the range 2.5–7.6MHz showed that reliable transmission is possible when signal to noise ratio exceeds 14dB and when receiving location is well characterized empirically prior to link deployment.
The Superconducting Magnet Division at Brookhaven National Laboratory (BNL) is making and testing 20 insertion region dipoles for the Large Hadron Collider (LHC) at CERN. These 9.45 m-long, 8 cm aperture magnets have the same coil design as the arc dipoles now operating in the Relativistic Heavy Ion Collider (RHIC) at BNL and will be of single and twin aperture cold mass configurations. They will produce fields up to 4.14 T for operation at 7.56 TeV. The magnets will be tested at 4.5 K using either forced flow supercritical helium or liquid helium. This paper reports the results of tests of four D1 magnets, including spontaneous quench performance, verification of quench protection heater operation, and magnetic field quality.