Abstract: A signal source from a transmitter is down-converted by being mixed with a locally generated signal so that a desired adjacent channel band is converted to base band and the adjacent channel power measured after filtering by a low pass filter. To eliminate the notch in the filter characteristics that occurs when the power is measured by a.c coupled means, the locally generated signal is modulated or swept around the center of the adjacent channel band.

Abstract: A frequency synthesizer which is capable of providing very high output frequencies of the order of 500 MHz is designed to produce a very pure signal having very low noise. An overtone crystal oscillator which is constrained to oscillate at a harmonic frequency of the fundamental frequency determined by the physical dimensions of the crystal is mixed with a variable low frequency signal which is varied to provide the necessary output frequency steps. It is not possible to adjust the frequency of the overtone crystal oscillator without degrading its stability and introducing noise, and any departure of the frequency to the overtone crystal oscillator from its nominal value is compensated by adjusting the low frequency oscillator.

Abstract: A control device which is suitable for use with electronic apparatus is used to scan a range of signal or data values, such as a frequency spectrum, and to cease scanning when a selected parameter is found. The scanning operation is driven by a d.c. ironless motor which, once it has been initially spun by hand, continues to rotate until the selected parameter is detected.