Let us suppose I don't have a DDS available, and instead I have two square wave clocks with frequencies of my choosing. I have the impression that creating a wide bandwidth (multi-decade) sine wave could from this signal could be done two ways. In the first way, you use only one square wave clock, and you low pass filter through a switched filter bank, with a cutoffs positioned to deal with the odd harmonics (and I suppose whatever even harmonics are generated by parastics). Alternatively, it seems like you could fix the frequency of one square wave, use a crystal filter to get a pure tone, and then mix it down by driving a mixer using the other square wave as a swept frequency LO. As long as the square wave is of high enough frequency, you only deal with harmonics of the LO, which can be trivially filtered. I also understand that a properly designed mixer will suppress harmonics of the output signal... Marki's mixer have excent nlo+nrf figure. This second strategy would seem much easier as it doesn't require a switched filter bank. Have I understood this all correctly?