The Amazing All-Band Receiver

Looks like direct conversion receiver with 2 kHz and 28 kHz injection to hear sound and ultrasound superimposed on different fm and am carriers. This modification is based on a Soviet Cold War device, the Sinitsa, acording original author. A carrier frequency, just above the audio range, is added into the incoming signal to produce a host of sidebands. The result is that just about any signal, even a dead carrier, will produce a detectable audio output. I think the audio from the oscillator could be injected into the bottom side of the 10k bias resistor, eliminating the need for the 10 uH choke. Maybe the 10k resistor is replaced with a 10k trimmer and the wiper of the trimmer goes to the op amp through another 10k in series with a 1 uF cap to save a little current. Alternately, add a 1k in the ground leg of the 10k and hook the wiper of the pot there. It might be interesting to make the frequency of the injected square wave variable and with very sharp edges, perhaps from an AC logic device. Lots of experiments to try here!
http://www.techlib.com/electronics/allband.htm
http://www.cryptomuseum.com/df/sinitsa/
Original author inspiration, all band receiver device Sinitsa.