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One problem is the keying rate will produce sidebands which overlap. Some very clever signal processing which reconstructs the message from one and then subtracts its spectrum from the total to leave the other can be done, but it will probably take the resources of a national espionage agency.
you can use the DDS to transmit the 1Hz spacing CW signals,and use the FFT method to disciminate the two CW signals!
but i think it is meaningless to do this
I Agree springf2000.
In my job, some colleauges have been done this.
The received CW signal with milliHz resolution.
The detection technique was "wired digital", i don't know nothing more about.
But also the RF hardware is important, especially the frequency stability of the Local Oscillators.
Calling dF the discrimination frequency, and Fo the carrier frequency, the ratio dF/Fo give an idea of the required time stability for the TX and RX LO's.
I.e. a good ovenized quartz is in the 1E-8 range that means 1 Hz of jiitter for 100 MHz carrier.
For Higher Fo a more stable LO is required (Rb, or Cs).
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