The problem that we are dealing with is the 180 MHz clock
feedthrough in the output. It was discovered when turning the RF
off, but it is present with the same amplitude when it is on,
where it matters. RF is turned off for special purposes only, not
while measuring, and for me it is ok as is.
BTW, I plan to test the transformer method, as indicated by
Clifford and also used in some versions with the Chinese modules
and in the experimenters board. I have to get a Minicircuits T1-1T
transformer for best results, and this will not happen until
73 de Ignacio EB4APL
El 10/07/2017 a las 22:28,
Perhaps a better way to turn OFF the RF would be to put
the DDS chip in sleep mode, NOT to just program it to
0Hz. IIRC, putting it to sleep also powers down the
internal clock multiplier (AD9851).
73, Terry, N4TLF