Paragraph 2 General description of measuring apparatus

The measuring apparatus shall be a calibrated radio receiver, covering the frequency range 40 Mc/s–70 Mc/s, designed for the measurement of the field-strength of radio frequency noise. For this measurement the input terminals of the receiver shall be connected to a dipole aerial by a balanced screened feeder. The receiver shall be of the superheterodyne type and comprise a radio-frequency (R.F.) amplifier, a frequency changer, an intermediate-frequency (I.F.) amplifier and an output valve-voltmeter. Attenuators, calibrated in decibels (db), shall be provided in the input circuits of both R.F. and I.F. amplifiers. The indicating meter of the valve-voltmeter shall have a scale provided with zero and full-scale marks and a reference deflection mark at mid-scale. The measuring apparatus shall be calibrated in terms of a known intensity of a continuous wave field in which the associated aerial system is placed. Facilities shall be provided so that, whenever a measurement is to be made, the gain of the receiver of the measuring apparatus may be set to the gain used when it was calibrated.