RF

100 MHz RF oscillator with ATtiny12

A frequency reference for tuning up the RS-232 to 100 MHz RF desktop channel adapter elsewhere on this site, when I found this Saronix crystal oscillator in my junk box. A few minutes with AVRStudio produced an ATtiny12 to make a tone - even fewer parts than using an NE-555. With the addition of a transistor to gate the output, I was set to go. Quick and dirty, but it was useful. The Saronix oscillator has an open emitter output. When the 330 Ohm load resistor on the output is grounded, the RF out of the oscillator increases. Modulation is affected by driving the MPSH34 on and off to switch the 330 Ohm load resistor. ..

16-300 MHz Testing Colpitts oscillator

The circuit is a modified Colpitts oscillator, tuned with MV209 varactor diodes. The resonating inductor and the drain choke are selected by a rotary switch. 1N5711 Schottky diode, D, clamps the maximum positive voltage on the gate of oscillator FET, Q1 to just above ground to reduce the distortion in the wave form on the gate of Q1. Buffer Q2 provides about 1.8 volts peak-to-peak at 20 MHz to drive a frequency meter. Since the P-P voltage on the gate of Q1 is too large to be buffered by a 2N5485 without sever distortion -see the pictures further down this page), the signal is reduced by a capactitive voltage divider formed by 1 picofarad capacitor C11 and the input capacitance of Q3. This results in about 650 millivolts on the gate of Q3, and about the same on the source. ..

187 KHz RF oscillator

An oscillator, a small power stage, some modulation, and a tiny loop antenna make RF for experiments on at 187.5 kHz on the United States' FCC Part 15 Lowfer band (1600-1750 meters). This is a low power signal source I put together one evening to provide 187 KHz RF signals for an anticipated receiver investigation. Under Federal Communications Commission rules inside the United States, one is allowed to operate a transmitter without a license under certain conditions. Here, I have copied the relevant section of the most recent version of the Code of Federal Regulations that I could find.. ..

100 MHz RF Oscillator Circuit

The following schematic diagram shows the design of a 100 MHz Radio Frequency RF Oscillator Circuit. The electrets microphone picks up and amplifies sound then fed it into the audio amplifier stage built around the first transistor. The output from the collector is fed into the base of the second transistor where it modulates the resonant frequency of the tank circuit (the 5 turn coil and the trim cap) by varying the junction capacitance of the transistor...

RF oscillator circuit (2N3904)

This basic RF oscillator circuit is easy to build and the components are not critical. Most of them can be found in your junk parts box. The L1 antenna col can be made by close winding 8 to 10 turns of 22 gauge insulted hookup wire around 1/4 inch form such as a pencil...

A current-feedback amplifier is a well-known component with many uses. Its basic block diagram shows that its input stage is a voltage followerin practice, a symmetrical emitter follower (Figure 1). The configuration samples the output current, converts it to voltage across a large impedance, and amplifies it to the output using a high-power, low-output-impedance amplifier...

Figure 1 shows a novel circuit that uses a low-cost, high-speed op amp as a crystal-controlled RF sine-wave oscillator. An op-amp oscillator offers several advantages. Because an op amp is a complete amplifier with a high-impedance input and a low-impedance output, it considerably simplifies the circuit design by replacing the traditional multiple-transistor circuit with its interstage transformer and numerous other components...

This circuit is similar to schematic CMOS INVERTER 125KHz LC OSCILLATOR but inverts the LC components so the inductor is grounded. Two inverters are needed to produce the needed oscillation. Again, the values shown set the frequency at 125KHz but can be changed to produce other frequencies...

This circuit uses a single CMOS inverter to form a series resonant LD oscillator. The values shown set the oscillation at about 125KHz buth other frequencies are possible by changing the main LC values...

I have used this parallel resonant LC oscillator circuit countless times. The oscillator frequency is determined by the inductor and capacitor values. I have shown an adjustable inductor to make it easy to set the frequency to a specific value. Once set the frequency is fairly stable over supply voltage variations and temperature changes. The values shown are for 125KHz but the frequency can range from tens of kilohertz to tens of megahertz. With a 74HCU04 type inverter, it will oscillate down to about 1.5 volts...

If you need a clean emitter coupled logic (ECL) type signal between 200MHz and 400MHz this circuit works fine. It uses four voltage-controlled capacitors to change the frequency...