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THis Wien bridge oscillator is very simple and as every wien oscillator has low distorsion and the resonance frequency can be easily adjusted. This frequency depends on a pair of resistors and a pair of capacitors and is defined by the formula: F = 1/2ΠRC. In this wien oscillator circuit, R is formed by R1 + P1a (or R2 + P1b) and C is C1, C2 or C3 (or C4, C5 or C6).
Another great quartz crystal oscillator schematic with bb139, a 2-nd harmonic quartz crystal and one BF214 transistor. So, the Q quartz is half of the desired transmitter frequency, L1 has 24 turns, 0.08mm Ø built on a 455kHz carcase. L2 has 8-9 turns / 0.8mm Ø / 5mm Ø. This quartz oscillator circuit has a great frequency stability, I’ve build it.
Crystal quartz circuit components
Nowadays, it is no longer necessary to use discrete components to build oscillators. Instead, many manufacturers provide ready-made voltage-controlled oscillator (VCO) ICs that need only a few frequency-determining external components. One example is the RF Micro Devices RF2506. This IC operates with a supply voltage between 2.7 and 3.6 V (3.3 V nominal) and provides a low-noise oscillator transistor with integrated DC bias setting.
A very simple crystal quartz oscillator circuit schematic which use a quartz for frequency stability and a good rf tranzistor. Use a 2-nd or 3-rd harmonic crystal , for example if you want 100MHz use a 50MHz or 33.3MHz quartz or if you want use a 4-th harmonic crystal but the output rf voltage will be lower. The L coil has 5 turns 0.8mm Ø , 6mm Ø , 1 mm step, output at first turn from + . Use C4 for fine frequency adjustments.
For a great frequency stability, this quartz oscillator circuit must use a good varicape diode (you can use bb139).
