Close up of the receiver board. mounted to the loop antenna. You'll notice a number of the components differ from the markings on my overlay. Originally I intended to use BC549 transistors, I substituded BC109C's as I had no BC549's in stock. The overlay and circuit diagrm incorperate all these changes.

A Voltage-Controlled Amplifier (VCA) made from three BC549 NPN transistors and three BC214 PNP transistors. It's a Gm Cell with variable current followed by a simple op-amp.

The input is rigged up to an HP 4204A Oscillator with a 3310A Function Generator supplying the modulation signal. Output goes to a Tek 5440 analog oscilloscope and an X-Mini capsule speaker.

A Voltage-Controlled Amplifier (VCA) made from three BC549 NPN transistors and three BC214 PNP transistors. It's a Gm Cell with variable current followed by a simple op-amp.

The four traces shown on the Tek 5440 are the input (1kHz), the two intermediate signals and the output. The control or modulation voltage was a sinewave in this case.

A Voltage-Controlled Amplifier (VCA) made from three BC549 NPN transistors and three BC214 PNP transistors. It's a Gm Cell with variable current followed by a simple op-amp.

The four traces shown on the Tek 5440 are the input (1kHz), the two intermediate signals and the output. The control or modulation voltage was a triangle wave in this case.

24 werte ZU-92 Transistor Sortiment Assorted Kit Jeder BC327 BC337 BC517 BC547 BC548 BC549 2N2222 3906 3904 5401 5551 C945 1015

ZTX series transistors and BC547/BC548/BC549 and BC557 series transistor pin-outs

S/W Ver: A0.02.0ER