On 07/11/2010 11:50 AM, amdx wrote:
In a direct conversion receiver, does the osc. run at
exactly the same frequency as the received signal?

Assuming the answer is yes;
Is it possible to have a high Q LC front end at the output from the
antenna,
split the signal and feed one output to the rf input of the mixer and feed
the other splitter output to an amplifier and use the amplified signal to
drive the osc input of the mixer?

Simple block diagram of proposed idea;
http://i395.photobucket.com/albums/p...conversion.jpg

NO, for the same reason you can't fake the BFO at the final detector the
same way. You need to (re)inject a carrier to receive a CW or SSB
signal, and the receiver must supply this carrier. A direct conversion
receiver is just a tunable IF, detector, and BFO without a superhet
front end. There ARE synchronous AM detectors that do what you propose,
but this works because the incoming carrier is already there.