Here's a 1980s shortwave rig. It did about 8 Watts carrier and about 40 Watts peak on 48 metres. The synthesiser allows it to be set on any frequency within the range of the VCO in 5kHz steps. It uses a standard 4MHz crystal for reference. The transformer is a 100V line type, which we found to work really well for modulation. It has a simple active audio lowpass filter at 4.5kHz and was fed from pre-recorded, processed tapes. Into an inverted-V aerial, with a good earth, it got a remarkably good signal from East Anglia into a lot of Europe. We had regular listeners in Poland and Ukraine, so it got out well eastwards!
The eagle-eyed amongst you might notice that there's no power provision - we had a little 90VA switched-mode PSU in there (subsequently stolen for another project). It would also run very well from two car batteries in series.
See - it's not difficult!
