The unit described here is simple to build, and can be quite small. The picture below shows the prototype, in a box 175mm wide, 210mm deep and 55mm high. The single circuit board is 140 x 90mm, so there's plenty of room inside for another board (a local control and LCD display board is planned). The design includes a linear amplifier, sine wave output and 60dB attenuator.
The Exciter uses a Direct Digital Synthesizer, made using a high speed microcontroller, to accurately generate radio frequency sine waves from zero to about 400 kHz. All the work is done by the inexpensive microcontroller, so no expensive DDS chip is need