HF radio... some tests

...almost there, at least the receiving part. Just finished the variable center frequency audio filter now the only thing missing is the AGC circuit due to redesign. Manual AGC is working. I still need to make the rf pre-amp and attenuator but they will not populate the main board. Next few days will try to start the transmiting part.

Variable center frequency audio filter at: http://py2rlm.sites.uol.com.br/filtroegl.HTM



















In the video the first control used is the variable audio filter (shcematic above) then the switch to put "on" the audio notch filter and then USB/LSB selector. The filter are not perfect because not much care was made to ensure equal components on both opamp's.