[HomeBrew] Direct conversion questions

[R. Blackman]

Hello to the list

I am playing with direct conversion qrp receiver designs to go along with my 
AD9851 DDS VFO.

Question 1) in the dc receiver designs which use a minicircuits SBL-1 mixer, 
they show a direct connect to the input filter after the antenna. Does the 
microvolt RF from the antenna actually make it through this mixer to the 
audio amp without an rf amp before the mixer? Every design I look at show a 
direct connect to the antenna / filter.

Question 2) in DC designs which use the NE602 / SA612 mixer, which has gain, 
I have not found a design yet which takes into account the 1.5K input and 
output impedance of the SA612. Again, they show a direct connect to the 
antenna / filter on the input and out to an audio preamp on the output.

Any comments from the wise?

my homebrew page:
http://va3ndo.tripod.com/index.htm

many thanks,

Richard VA3NDO