dsb exciter

Posted on Feb 5, 2014

A wideband circuit design of a Double Sideband Exciter. The circuit can be used to generate a low level signal with suppressed carrier or with any percentage of carrier injection that is desired. The circuit is simple and will easily provide an output 1 v p-p into a 75 ohm load depending on selected gain. The exciter can be used as a Direc

dsb exciter
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t Conversion exciter by providing an oscillator at the operating frequency. In an application where another stage of mixing will be used, an I. F. oscillator can be provided to the exciters input. A composite AM signal will be output from the exciter and it can drive succeeding stages of a transceiver or other transmitter. The following schematic illustrates the design. There are no frequency limiting components involved so the output will provide as good a quality as is placed at the audio input. The block Diagram of Figure 1 illustrates the basic operation of the exciter. The output of the Mixer stage is the product of the audio input and the oscillator input. This simple method produces a double sideband output with suppressed carrier signal. It is important to match the amplitudes of the input signals to around 1 v p-p so the output will not exceed the dynamic range of succeeding stages. The Summer stage will allow carrier to be injected to the signal for double sideband full or some percentage of suppressed carrier depending on the adjustment of the injection potentiometer. The output of the Summer stage is passed to a gain of 2 output buffer. This stage will drive 75 ohms at a low level of around 10 mwatts rms. Subsequent gain stages can be added to increase power output as long as they are operated linearly. One caution should be observed. There are no filters to limit harmonic content of this exciter. As long as...

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