On Jul 1, 8:19 am, wrote:
Noise figure and spurious responses are really determined by RX input
filters and the first stages of RF amplification. generally at VHF
and above you do not get an acceptable NF without an RF amp
for communications uses.

I was considering a Hittite HMC580ST89 InGaP HBT Gain Block
which has a NF of 2.8, covers DC - 1 GHz, and is easy to use
(i.e. can operate directly from +5V).

The mixer will produce spurs from several causes..
Dirty LO source, for that range I assume you using a carefully
designed PLL as DDS has many discrete spurs.

Currently the design calls for using a AD9952 DDS followed by
a 10.7 MHz BW=300 kHz crystal filter to provide the reference
for a ADF4002 PLL controlling a UMC VCO. ADIsimPLL claims
phase noise of -107 at 10 kHz.

-- John