Annex 1
�1���� Antenna installation
������� 1.1���� Frequencies below 30 MHz
It is recommended that, for frequencies below 30 MHz, vertical or loop antennas
be used. A vertical antenna shorter than one-quarter of a wavelength may be
used, with a RF ground system consisting of either buried radial conductors at
least twice the length of the antenna and spaced 30� or less apart, or an equivalent RF ground screen. An inverted
cone type vertical antenna with a similar ground system may also be used with
some advantage.
����������������� 1.1.1���� It is generally accepted that random variations in
polarization of ionospheric waves are such that the vertically polarized
component is, in general, substantially equal to the horizontal component.
����������������� 1.1.2���� The voltage developed at the output of a passive
vertical antenna shorter than one quarter of a wavelength is substantially
dependant on the frequency. Since the impedance of this antenna is capacitively
reactive, the subsequent voltage response in a field-strength measuring
instrument, when connected to a properly terminated transmission line, is
essentially a direct function of frequency, resulting in a simple, relatively
uniform calibration curve.
������� 1.2���� Frequencies between 30 MHz and 1 GHz
������� 1.3���� Frequencies above 1 GHz
Antennas for field-strength measurements at frequencies above 1 GHz are usually
directional. Their antenna factor (k-factor, see � 1.4) can be
determined with high accuracy. Due to the directional characteristics of the
antennas the influence of the environment on the measurement accuracy is
normally low.
������� 1.4���� Antenna factor
�2���� Receiver
�3���� Calibration
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