Electronic CW Keyers

• Electronic Keyer - F5JTZ
• Iambic Touch-Keyer - YC5NBX
• Simple CMOS Keyer - OH7SV
• Simple Electronic Keyer - N1HFX
• CW Electronic Keyer
• CMOS Iambic Keyer - N5FC
• All-BJTs Keyer
• CW Keyer - YO3APG
• Deluxe All-Solid-State Iambic Keyer - W1RML
• Electronic CW Keyer - YO3CZI
• Single-IC CW Keyer - W9HFM
• CW Keyer with NE555
• Memory Keyer - AI2T

Miscelaneus Circuits

• High Dynamic Range Noise Blanker
• Left / Right Revolution Counter (for tuning)
• Active Baluns - Differential to Single Ended
• Active Baluns - Single Ended to Differential
• RF Activated Tone Monitor
• PTT Delay Circuit - W3KKC
• HF QRP Manual Tuner - W6JJZ
• Ultrasonic Proximity Detector
• Multi-Q Receive Loop Antenna
• Phase Detector with Discrete Components EK47-Receiver
• Low-Cost FSK Generator
• Satellite Finder
• Electrostatic Detector
• HF Line Coupler
• 4:1 Broadband Transformers
• Noise Blanker
• Balun Transformers
• Helical Resonator Dimensions
• Crystal Filters Types
• Laser-Torch Wireless Communication
• LNB 13V/18V H/V Switch
• Modulation Circuit for SHF Beacon
• AGC with Squelch Control
• AGC with AM Detector
• Receiver AGC with hang threshold
• AGC / S-meter - PY2MG
• AGC Audio Preamplifier
• Glitch Detector
• 10 MHz SSB Ladder X-tal Filter
• 27 MHz - 40 MHz Lumped Component Diplexer
• 430 MHz to 780 MHz Tunable Filter
• 433 MHz Lumped Components Balun
• RX/TX 27 MHz Remote
• Air-Speed Sensor for Cooling Fan
• 3xFETs Noise Blanker
• Active RF Isolator
• Low Frequency Active Isolator/Circulator - Wenzel
• Antenna-Tuner for QRP
• RIT for VFO Transceivers
• 3.58 MHz CW Ladder Filter - N2DCH
• 90-degrees Phase-Shifter for IQ-modulation
• Power Combiners / Dividers - RSGB
• S-meter 120dB Dynamic Range - DC4KU
• Variable Bandwidth X-tal Filter - G3UUR
• Broadband Transformers
• Prevent Thermal Runaway for BJT Power Amplifiers
• Temperature Compensation for X-tal Oscillators - I6MCF
• 500 kHz - 30 MHz Antenna Tuner
• Variable Quartz Filter

Microwave Circuits

• Microwave Motion Detector
• Biasing Microwave GaAs FET's
• UHF Doppler Motion Detector
• 2.4 GHz Prescaler
• Divide by N using 74160 - Wenzel
• Staircase Frequency Divider - Wenzel
• Frequency Counter Prescaler
• 12 GHz : 1000 Prescaler - DG6RBP
• Quarter-wave Coaxial Baluns
• UHF Movement Detector
• Bias-Tee 5 kHz to 3 GHz
• Microwave Coaxial AM Diode Detector
• Microwave FM Diode Detectors
• Microwave Microstrip AM Diode Detector
• Power-Combining using Wilkinson Dividers
• Distributed Wideband Balun for Microwaves
• Microstrip Couplers
• Microstrip Stubs
• Phase Shifters Topology

Power Supply

• DC Protection Circuits
• Overvoltage Protection
• Power Supply 13.8V/20A
• 12V Battery Charger
• 13.8V Float-Charging Power Supply
• 28V / 20A Power Supply
• Low Noise Power Supply for Audio Amplifiers
• Power Supply with Noise Clean-up Circuit - Wenzel
• 13.8V / 10A Power Supply - N1HFX
• 13.8V / 40A Power Supply - OZ2BKK
• 13.8V / 25A Power Supply - F5JTZ
• 28V / 50A Power Supply - F5UAM
• 1.25V-25V / 2.5A Power Supply
• DC/DC using a Linear Regulator
• High Voltage DC/DC Converter

Electronic CW Keyers

• Electronic Keyer - F5JTZ
• Iambic Touch-Keyer - YC5NBX
• Simple CMOS Keyer - OH7SV
• Simple Electronic Keyer - N1HFX
• CW Electronic Keyer
• CMOS Iambic Keyer - N5FC
• All-BJTs Keyer
• CW Keyer - YO3APG
• Deluxe All-Solid-State Iambic Keyer - W1RML
• Electronic CW Keyer - YO3CZI
• Single-IC CW Keyer - W9HFM
• CW Keyer with NE555
• Memory Keyer - AI2T

Audio design

• Active CW Filter and Audio Amplifier
• Dynamic Noise Filter
• Microphone Preamplifier Electret
• Microphone Speech Processor
• Microphone Amplifier Low/High Impedance
• Class-A Headphone Amplifier
• Class-A Audio Amplifier
• Speech Processor - TL081
• Variable CW Bandpass Filter
• Variable CW Filter and Amplifier
• Audio Automatic Gain Control
• Baxandall Audio Filter
• Microphone Amplifier with ALC
• Audio Amplifier with mute control
• Noise Canceling Electret Microphones - WB9YBM
• Dynamic Microphone Preamplifier
• Speech Processor - All BJT
• Audio Preamplifier with Dynamic Noise Reduction
• Class-A HIFI Headphone Amplifier
• Super Class-A Low Distortion 3W Amplifier
• CW Audio Filter with Digital Selection - PY2MG
• Microphone Preamplifier with Tone Control - PY2MG
• Boosting Gain and Limiter of LM386 - VK3AWC
• Variable Audio LPF with MAX293
• 300 Hz - 3 kHz Microphone Filter
• VOX Circuit
• Voice Level Meter
• Microphone Dynamic Compressor
• 1kHz Sine Wave Oscillator
• High-Pass Low-Pass Microphone Preamplifier - N2MNN
• Passive Audio SSB-CW Filters - W3TS
• LC CW Band Pass Filters - DC8NR
• Audio Intelligibility Enhancer - N4GG
• Dual-Tone Audio Generator - VE3FIT
• RF Speech Clipper - DF4ZS
• 1W Audio Amplifier with Compressor
• Booster for Elektret Microphone

RF Test Circuits

• Capacitance Meter
• Field Strength Meter LM324
• HF Q-meter VK5JST
• Antenna Analyzer - F6BQU
• RF Power Calibrator
• VHF Wattmeter
• 88 MHz - 960 MHz Antenna Analyzer
• LED RF Power Meter - N9ZIA
• Return Loss Bridge
• Return Loss Bridge with AD8307
• HF SWR Bridge
• Grid Dip Meter 2 MHz - 20 MHz
• Field Strength Meter 3 Levels
• BandScope for 2m Band
• Lightening Detector
• 3-Digits Dip Meter
• Calibrated Noise Source
• Capacitance Meter using DVM
• Inductance Meter using DVM
• High-Impedance RF Probe
• DC to 500 MHz Log Detector/Amplifier - DJ1ES
• L-C-R Bridge - G3BIK
• Phase Meter
• Inductance Meter - VK5BR
• L/C Meter - IZ7ATH
• FM Deviation Meter
• Flicker-Noise Generator - Wenzel
• 2.4 GHz mW Power Meter - F1HDD
• Simple Crystal Tester - F5JTZ
• Inductance Meter - N5ESE
• Magnetic Field Meter
• RF dBu Meter
• Two chips LED Frequency Counter - PA2OHH
• 0-99 kHz Frequency Counter - G0UPL
• LED SWR/Power meter - PY2MG  
• Electro-Magnetic Waves Detector
• Long-Wave Lightening Detector
• Cable Reflection Tester - N9ZIA
• TDR Circuit and Signals - T.Engdhal
• 1 MHz to 1 GHz LED Absorption Meter - GW1TDV
• S9 HF Signal Generator
• Antenna Noise Bridge
• Audio Filter Analyzer
• True Linear RF Power Detector
• Grid Dip Meter 3.5 MHz to 110 MHz
• 1.6 MHz to 150 MHz Modulated Grid-Dip Meter
• Five Grid-Dip Meters
• 30 kHz to 30 MHz Sinusoidal Signal Generator
• Capacimeter using NE555
• 0-1uF Capacimeter
• Coil Short-Circuit Detector
• Fonometer
• All-BJTs L-C Meter
• VHF FM Signal Generator
• Sweeper for 455 kHz IF
• 500 kHz to 3 GHz LED Field-Strength Meter
• 2xBJT Capacimeter
• Varactor Capacimeter
• Automatic VSWR and Power Meter - W0INK
• RF Sweeper - VK2ZAY
• Very Low Frequency Survey Probe - VK2ZAY
• 1 MHz to 30 MHz Noise Source - G1HSM
• Capacimeter with 2xNE555 - WA8MCQ
• Dual-LED SWR Indicator for QRP
• HF In-Line Return Loss and Power Meter - N2PK
• SWR Bridge Tuner "Rainbow" - N2CX
• Spectrum Analyzer on the Oscilloscope
• Grid-Dip Meter with Digital Display
• Marker Generator - KB1MW
• Micro-Wattmeter - W7DB

ATV Transmitters/Modulators

• Audio/Video Transmitter
• AM TV Transmitter
• 23cm ATV FM Transmitter
• A-V UHF TV Modulator
• Crystal TV Video Modulator
• TV Audio-Video Transmitter
• Simple TV Video Modulator
• TV Modulator
• A-V Transmitter - ZP5ZDM
• A-V VHF Transmitter
• FM ATV Receiver
• UHF A-V 1W Transmitter
• 1296 MHz FM ATV Transmitter - I2ROM
• ATV FM Receiver-Demodulator
• 470 MHZ PLL FM Video Demodulator
• Two ATV FM PLL Demodulators
• 432 MHz ATV AM Transmitter
• 439 MHz ATV AM Transmitter
• 902 MHz PLL FM ATV Transmitter
• 1296 MHz 300mW FM ATV Transmitter
• 1296 MHz AM ATV Transmitter
• 1296 MHz FM ATV Transmitter - F3YX
• UHF 2W AM ATV Transmitter
• UHF 5W AM ATV Transmitter
• 1296 MHz PLL controlled FM ATV Transmitter - N9ZIA

RF Mixers

• Doubly Balanced Mixer MC1496
• Mixer Diplexer
• Dual MOSFET Mixer
• Microwave Mixers
• Stripline Quadrature Microwave Mixers
• High IP3 Mixer +40dBm - IK4AUY
• 1296 MHz Diode Mixer - WA6UAM
• Dual-FET HF Mixer
• High Dynamic Range HF Mixer
• High IP3 (33dBm) BJT Mixer
• 900 MHz BJT Gilbert Mixer
• HF Sub-Harmonic Mixer
• 1152-10368-24192 MHz Harmonic Mixer
• Microwave Harmonic Mixer
• 1296 MHz DBM with ferrite balun - WA6UAM
• 1296 MHz DBM with coaxial balun - WA6UAM
• Microwave Coaxial Diode Mixers
• Distribute Diode Single-Balanced Narrowband Hybrid Mixer
• Single Schottky Diode Mixer
• Two-BJT Product Detector
• Dual-Gate MOSFET Product Detector

RF Switch / Attenuator

• IF Filters Switching Circuit
• TX/RX RF Switch FET
• TX/RX RF Switch PIN
• RF Sensing TX/RX Switch
• RX/TX Quarter-Wave PIN Switch
• PIN Attenuator BAR61
• Variable PIN Attenuator 1dB to 20dB
• AGC with PIN Attenuator
• 4xPIN Diodes Wideband Switch
• Modulator-Demodulator using PIN Diodes
• Phase Shifter using PIN Diodes
• RF Attenuator Types using PIN Diodes
• RF Switch Types using PIN Diodes
• AGC PIN Attenuator
• Automatic Antenna Attenualtor 45dB range - RSGB
• HF 25W PIN Antenna Switch
• All Transfer PIN Switches
• PIN Diode Limiter
• SPMT PIN Switches

VFO Stabilizers

• 
  
  One chip VFO Stabilizer - G0UPL
• 
  
  VFO Stabilizer - PY2MG
• 
  
  VFO Stabilizer - PA0FRI
• 
  
  Huff-and-Puff VFO Stabilizer - WN5Y
• 
  
  VFO Stabilizer - PA0CMU
• 
  
  2 x Huff-and-Puff VFO Stabilizers - RSGB
• 
  
  40 MHz to 70 MHz 3-band Frequency Stabilizer - DC4KU

Oscillators

• 5 MHz to 5.4 MHz Variable Frequency Oscillator
• 6 MHz to 6.35 MHz Variable Frequency Oscillator
• 7 MHz to 7.3 MHz Variable Frequency Oscillator
• 30 MHz to 200 MHz VCO
• 50 MHz to 150 MHz Crystal Oscillator
• 50 MHz Crystal Oscillator
• 100 MHz Crystal Oscillator
• 100 MHz VCXO
• 455 kHz Ceramic Filter BFO
• Butler Crystal Oscillator
• Vackar VFO G3PDM
• High Power VFO - K7HFD
• Low Voltage Crystal Oscillator
• Parallel Mode Crystal Oscillator
• Series Mode Crystal Oscillator
• Variable Crystal Oscillator VXO
• 750 MHz Push-Push Oscillator
• Butler Overtone Crystal Oscillator
• High Overtone Crystal Oscillator
• 3 MHz to 30 MHz VCXO
• Low Noise Differential VFO - 5 MHz to 5.5 MHz
• VHF Oven Crystal Oscillator - W6PQL
• 1.3 GHz VCO with Emitter Noise Feedback
• 2 GHz to 4GHz VCO
• 220 MHz Low Noise Cascode Oscillator
• 600 MHz to 2.2GHz VCO
• 800 MHz to 2.2GHz Push-Pull VCO
• 1 GHz Differential VCO with Amplitude Control
• 10 MHz VXO
• 455 kHz Beat Frequency Oscillator
• Crystal Oscillators Types
• VXOs Types and Schematics
• 750 MHz to 1250 MHz VCO
• High Performance VHF Overtone Oscillator - GW4DGU
• Octave VCO with active bias
• 200 MHz to 400 MHz VCO
• 1700 MHz to 1950 MHz VCO
• Very Low Phase Noise Crystal Oscillator - Wenzel
• 1 GHz Very Low Phase Noise VCO
• 74 MHz to 105 MHz Low Noise VCO
• 100 MHz Low Phase Noise VCXO
• 125 MHz Very Low Phase Noise Oscillator - ADI
• 600 MHz to 1200 MHz Low Phase Noise VCO
• 18 MHz Stable and Constant Amplitude LO
• 1100 MHz to 1350 MHz VCO
• 70 MHz to 210 MHz VCO with Dual-Gate MOSFET
• 5 MHz to 6 MHz VFO - VE7CA
• 7 MHz VXO - NB6M
• 14 MHz VXO - NB6M
• 10 GHz DRO Oscillator
• 180 MHz X-tal Oscillator - F1ANH
• 5 MHz X-tal Coupled-Resonator LO
• 10 MHz Third-Overtone Pierce LO
• 10 MHz X-tal Cascode Oscillator
• 27 MHz Third-Overtone with TTL-output LO
• 40 MHz to 70 MHz VCO
• 42 MHz to 72 MHz VCO
• 100 MHz Fifth-Overtone Butler VCXO
• 110 MHz to 210 MHz VCO ESM500-Receiver
• 118 MHz to 198 MHz FM-Modulated LO
• 160 MHz to 260 MHz VCO ESV-Receiver
• 260 MHz to 520 MHz VCO HP8662A-SigGen
• 380 MHz to 520 MHz VCO
• 450 MHz Quarter-Wavelength VCO
• 567 MHz SAW Oscillator
• 800 MHz Very Low Phase Noise VCO
• Ceramic Resonator VCO
• HF Multiband VCO EK070-Receiver
• HF Multiband VCO ESH3-Receiver
• Low Phase Noise Push-Push VCO
• Third-Overtone VCXO with AGC
• 2.4 GHz to 2.8 GHz VCO
• 10.5 GHz DRO
• 102 MHz VCXO
• Cavity-Tuned Oscillator
• Butler X-tal Oscillators
• DC-Switched X-tal Oscillator
• FM-Modulated X-tal Oscillator
• 55.2 MHz VCXO - KA7OEI
• 1.93 MHz to 1.98 MHz Very Stable VFO - W8DIZ
• 5.05 MHz - 5.075 MHz Clapp VFO
• 1 MHz to 5 MHz Goral Type Oscillator
• 100 MHz Dual-Gate MOSFET Oscillator
• Triple Beat Frequency Oscillator
• 4.9 MHz to 5.5 MHz VFO - TS520
• 5.225 MHz - 5.575 MHz Franklin Stable VFO
• 7 MHz QSK VFO - NN1G
• Widerange VCXO W7ZOI
• 5 MHz VXO with ALC
• 21MHz VCXO - G3MEV
• Variable Crystal Resonator Oscillator - K2BLA