Reflex Radio Receiver
Posted on Nov 27, 2012 4894
The RF signal is passed from the antenna through CI to the tuned circuit made up of LI and C2. One end of L2 feeds th
e RF signal to the base of Ql for amplification and the other end ties to the junction of Rl and R2 to supply bias to the transistor. A 0.02-/xF capacitor, C3, places the "D" end of LI at RF ground. The amplified RF signal is fed through C6 to a two-diode doubler/rectifier circuit and then on to the volume control, R6. The wiper of R6 feeds the detected audio signal through C9 to the junction of Rl, R2, and the "D" end of L2. The "D" end of L2 is at RF ground, but not AF ground, allowing the AF signal to be passed through L2 to the base of Ql for amplification. The junction of the 2.5-mH choke and Tl is placed at RF ground through C5. The amplified audio is fed from this junction to the input of the 386 audio amplifier, Ul, to drive the 4" 8- speaker. The single transistor has performed a dual duty by amplifying the RF and AM signals at the same time.