Figure 4: Tuning in a National Weather Service weather broadcast at 162.471 MHz. This station uses narrowband FM. Image source: Digi-Key Electronics as in the spectrum analyzer display; the vertical scale is time. In the figure there are time markers showing the date and time. The third dimension is the signal power, which is indicated
The numeric readout on the top of the screen displays and controls the center frequency of the spectrum analyzer. The maximum displayed frequency range is the bandwidth of the receiver which is about 2 MHz. There is a horizontal zoom slider control to the right of the display. Zoom permits a horizontal expansion of the display about the center frequency ■ Beneath the spectrum analyzer display is a spectrum history display sometimes called a spectrogram, which shows the time history of the spectrum. The horizontal axis is frequency
plug (242204), providing the more common connector interfaces.
by the color. The default color scale runs from black, as the minimum power level, to red as the maximum power level. There are a variety of styles and color mappings available under display controls The signal displayed in Figure 3 is that of an FM broadcast station at 105.1 MHz. This is a wideband FM signal that has a bandwidth of 200 kilohertz (kHz). This is one of eight demodulators available in the SDR receiver. The other demodulators support narrowband FM, AM, upper and lower SSB, DSB, CW, and raw in-phase and quadrature signal components. The selections are in
SDR support software The SDR# software connects with the receiver and provides the user interface and visual display (Figure 3). The SDR# default user interface has three major elements: ■ The column on the left contains
controls for the SDR device. There are fourteen pull down
menus controlling all aspects of the SDR receiver. The principal controls are for the radio, audio, and display ■ The top grid contains the spectrum analyzer display. This plots frequency on the horizontal axis and signal power vertically using a logarithmic scale calibrated in decibels. Spectrum analyzers are the primary test tool used by RF engineers to measure and analyze RF devices.
The antenna connection on the receiver is via an MCX connector. The MCX jack on the receiver accepts a plug mounted on the antenna cable, or the supplied antenna can be replaced with a custom antenna
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