It was checked that 1 dB attenuation change also resulted in a 1 dB change of reading. To check the proper behaviour of the set-up, a 1 dB step attenuator was put in-line between the two-stub tuner and the diode mount. The level differences wereĭirectly read off the dB scale on the HP415. A HP 415 tuned amplifier was used to show the received signal levels.įor measuring the gain using s substitution method, first was the reference level established with the NBS antennas at each end, and then the tested antenna was substituted at the receiving end. The output was in the 100-200 mW range.Ī gain reference, the NBS standard gain antenna, was used at the transmitting end.Īt the receiving end, either the antenna under test or another NBS standard antenna was used, together with a two-stub tuner and a GR diode mount operating in the square-law region. We used GR unit oscillators on about 900 MHz, and their associated power supply with integral 1 kHz square-wave modulation. There were two assignments dealing with antennas, one to measure the gain of corner reflector using the substitution method, and the other plotting both the azimuth and elevation patterns of a small Yagi. Exactly what you describe was done as lab assignments in the Microwave Engineering course during the third year of my Uni studies in 1979.
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