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Continuous Coverage V.F.O. for H.F. - Timing and oscillator circuit diagrams / circuit schematics __ Designed by Francesco Morgantini IK3OIL Convert any signal to exactly 50% duty cycle - 06/25/13 EDN Design Ideas: How would you process a variable frequency signal to always maintain a 50% duty-cycle? Here's one way Design by Jim McLucas
DDS/PLL based VFO synthesizer - Timing and oscillator circuit diagrams / circuit schematics __ Designed by Aleksander Stare
Direct Digital Synthesis VFO for HF Bands-based on Analog Devices AD7009 DDS - Timing and oscillator circuit diagrams / circuit schematics __ Designed by Francesco Morgantini IK3OIL
FET Oscillators - This circuit comes from the Progressive Communications Receiver that is in most of the recent ARRL Handbooks and the article "A Progressive Communications Receiver", by Wes Hayward and John Lawson, QST, November 1981
1. __ Designed by Web David White, WN5Y
Frequency Reader for conversion VFOs - If you are interested in improving the mechanical frequency reading of your home made transceiver, or if you want to equip your old RIG with a digital reader, this may be the project for you. It is simple enough to assure a good and sure result also to beginners, and it doesn't require any microprocessor programming, in fact the only components employed are simple and conventional CMOS
ICs. __ Designed by Francesco Morgantini IK3OIL
Huff-Puff Stabilizer - The credit for this circuit goes to Hans Summers, who developed the circuit after my suggestion that magnetic coupling would work with a frequency stabilizer. It uses a shift register (74HC4517) as a memory for the stabilizer and provides excellent stability __ Designed by Web David White, WN5Y
K7HFD Low-Noise Oscillator - This circuit appears in the ARRL 2000 Handbook
4.18, and in Solid State Design for the Radio Amateur, by Wes Hayward & Doug DeMaw
26. No buffer is necessary with this VFO. There is enough drive to go directly to a diode mixer. __ Designed by Web David White, WN5Y
NE602 VFO Oscillator - It's my opinion that the NE602 may have been overlooked as one of the most stable VFO oscillators around. In the Signetics App Note "Applying the Oscillator of the NE602 in Low Power Mixer Applications", the NE602 is described as a chip with three subsystems, a Gilbert cell mixer, a buffered emitter follower oscillator, and RF current and voltage regulation __ Designed by Web David White, WN5Y
PIC16F628 controlled FLL (Frequency Locked Loop) VFO for HF - Microcontroller based electronic circuit __ Designed by Francesco Morgantini IK3OIL
Simple Circuit Frequency Reader for conversion VFOs - If you are interested in improving the mechanical frequency reading of your home made transceiver, or if you want to equip your old RIG with a digital reader, this may be the project for you. It is simple enough to assure a good and sure result also to beginners, and it doesn't require any microprocessor programming, in fact the only components employed are simple and conventional CMOS
ICs. __ Designed by Francesco Morgantini IK3OIL
Variable Frequency Oscillator - The first stage built was the VFO shown above in Figure 1. The oscillator portion is based upon Figure 4.15 from EMRFD. The VFO resonator tank is isolated from the JFET by tapping down as shown. This is an outstanding VFO topology. __
VFO Buffer - In the first design of the receiver, this buffer was used with an FET VFO oscillator followed by a filter and a 2N5109 amplifier. __ Designed by Web David White, WN5Y
VFO from 2001 ARRL Handbook
4.20 - Schematic only __ Designed by Jim Osburn, WD9EYB
VFO/Buffer - It's basically a standard Hartley oscillator, followed by Roy Lewallen's buffer (page 14.20 of the 2001 Handbook). Output is +7 dBm into 50 Ohms. Don't be tempted to add a gate diode, this circuit doesn't need it, and it will degrade the phase noise performance, according to Ulrich Rohde. It should be suitable __ Designed by Leon Heller |
