Prototype Radio III - WSPR RX

Using the prototype radio from THIS post I added a simple one stage 2N2222 audio amp and after working out the frequency offset of the Si5351 clock module I was able to get successful WSPR decodes. I am driving the audio from the amp directly into the mic input of the PC and using the WSPR v2.12 software. This new version has a I-Q mode that I am taking advantage of to bring the receiver pass band up in frequency a bit. This is normally used with a SDR like a softrock but it will also work with this simple direct conversion (DC) receiver. I am currently using a Fiq in  the software of 3000hz (3Khz). This is to get the pass band out of the lower noise region  of the DC receiver (sort of a low IF). I will try higher Fiq settings later to see if there is a difference (default is 12Khz).

This is the circuit I am using. Not shown is the Si5351 clock module and the 10db 50 ohm pad used to feed the VFO input. This circuit with my simple dipole antenna and the WSPR software has achieved decodes of station from 600 to over 3000 km on 30 meters today.

This is my current Si5351 LO frequency shown below. I have not performed a calibration on my Si5351 yet which would allow the corrected frequency to be displayed (looks like it about 100hz low). This LO of 10.135.500 hz plus the 3khz I-Q mode IF of the WSPR software places me at the equivalent dial frequency of 10.138.700 hz and the WSPR tones begin 1500 hz above that with a frequency of 10.140.100 to 10.140.300 (a 200 hz wide bandwidth).

I continue to be impressed with the Si5351 clock module and this experiment validates its stability. I want to continue to work on this receiver to see how minimal I can make it. This receiver currently has no filtering to speak of outside of the antenna tuner I use to couple to my dipole. I plan to try plug-in band-pass filters and expand it in to a minimal transmitter as well.