gnuradio module usage

• Signal Sources
• Noise Sources
• File Source / Sink
• Audio Source / Sink
• Add Signals
• Adding a Constant
• Complex Conversions
• Calculated and Arbitrary Waveforms - vector source
• FIR Filter
• gr.keep_one_in_n

This is a 'reflex' circuit - the two tubes in the middle serve double duty, amplifying the RF signal, then after detection by the tube on the right they also amplify the AF for the audio output tube on the left.