What is interesting is the simplicity of the approach (ignoring the hidden
cost of the ubiquitous PC), but it ignores the multiple harmonics that
come out of DDS chips.

So, if you were to working at, say, 3MHz, how would youknow that you were
not actually analysing responses at 6, 9, 12, 15, etc MHz?


http://sdr-kits.net/DG8SAQ/VNWA/Baier_VNWA2_QEX.pdf

But it does raise one question, and that is, who is fooling who about
its purchase price of ooo £450, for there cannot be more than about £40
in its component costs?