[HomeBrew] Direct conversion receiver

[R. Blackman]

Hello to group, and best wishes for 2010

I have completed a fun all band transceiver project using a AD9851 DDS  synthesizer, run by a PIC microcontroller.
There are relay switched bandpass filters, and a relay  TR / TX switch.

The receive module is based on the MRX-40 DC receiver as seen in CQ and other places:
   http://www.w5usj.com/images/surfacemount/mrx40-smt-schem%20v3.pdf

I have replaced the  MRX-40 oscillator with the DDS input, and the input filter / gain pot with the bandpass filters.

Question for the group: 

although selectivity is very good, the sensitivity is weak. If I inject a signal generator in place of the antenna, wow, nice and loud!
I tried placing a MAR-4 gain block as an RF pre-amp in the receiver, but was blown away by local AM broadcast stations.
Should I just use another audio gain stage before or after the LM386 amp?  Or try another way of  getting RF gain?

Does anyone on list have some suggestions to improve the receive sensitivity , ( read: Loudness? ) in a simple DC receiver.

many thanks,

Richard  VA3NDO

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