Circuit Library

Circuit Library

Circuits and articles for QRP builders, each with its source and errata.

9 of 9 circuits

40 m 7th-order Chebyshev Low-Pass Filter (7.5 MHz)

Filters › low-pass40m470 pF silver mica

The low-pass filter for the beginner's experimental transmitter in Experimental Methods in RF Design, Chapter 1.

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2 W Bipolar Power Amplifier, 7 MHz (MJE181)

Amplifiers › power40m12 VMJE181 NPN

The power amplifier of the beginner's experimental transmitter in Experimental Methods in RF Design, Chapter 1.

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W7EL Two-Transistor Feedback Buffer Amplifier

Amplifiers › small-signal80m 40m 30m 20m12 V2N3904 (MMBT3904 for SMD)

A buffer by Roy Lewallen, W7EL, shown in Experimental Methods in RF Design as Fig 2.79, often used as an oscillator buffer.

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Hartley VFO with 2N4416 JFET

Oscillators › lc-vfo40m8 V2N4416 N-channel JFET

The basic Hartley oscillator in Experimental Methods in RF Design, Chapter 4.

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Direct-Conversion Receiver, 40 m (TUF-1 DBM)

Receivers › direct-conversion40m12 VMini-Circuits TUF-1 double-balanced mixer

A direct-conversion receiver example from Experimental Methods in RF Design, Chapter 6.

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Common-Gate J310 RF Amplifier

RX front ends › rf-amp40m 20m 15m12 VJ310 N-channel JFET

A front-end amplifier from Experimental Methods in RF Design, Chapter 6.

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1:1 Trifilar True (Current) Balun

Matching › balun80m 40m 30m 20m 17m 15m 12m 10mFT-37-43 ferrite toroid

A 1:1 current balun from Experimental Methods in RF Design, Chapter 3.

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LM317 Dual-Output Bench Supply

Power › linear-regulatordc20 VLM317 adjustable regulator

The beginner's bench supply in Experimental Methods in RF Design, Chapter 1.

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Return-Loss Bridge

Test gear › bridge160m 80m 40m 30m 20m 17m 15m 12m 10m51 ohm 1% resistors

The classic return-loss bridge from Experimental Methods in RF Design, Chapter 2.

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