This is a simple FM transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project.With some modification, I create my own version of FM Telephone bug complete with stripboard layout. Theoritically, the frequency range is... [ more ]
This is a nice PLL FM transmitter with LCD display, PLL generated by TSA5511 I2C synthesizer controlled by PIC16F84 microcontroller. Output fequency can adjust from 88 to 108 MHz with 50 KHz steps.This very stable FM transmitter based on TSA5511 synthesizer from Philips. Frequency is performed with three buttons through PIC16F84 microcontroller and displayed on single line 16x1 LCD.With best of 2SC1971 final amplifier circuit design... [ more ]
A linear power supply has a transformer that steps down the line voltage to some voltage, a rectifier and a filter capacitor transform the low voltage AC into a moderately filtered DC that still is unregulated and has some ripple. Finally, a regulating circuit "burns off" the excess voltage, leaving only the exact amount desired at the output, typically 13.8V for communication equipment.One typical mistake made by many amateur designers is... [ more ]
RFSim99 is a free RF Simulation software that can help you in your RF Projects, especially if you are trying to design radio filters. RFSim99 works with S-parameters.This means that not only will it simulate and analyse circuits built out of its internal library of components, but that it can accommodate any circuit block or stage for which these are known.RFSim99 is a free linear S-parameter based circuit simulator offering schematic... [ more ]
Here's a schematic reference for building Elliptical (Cauer) RF Low-pass Filter for FM Amplifier 88-108 MHz. A ninth-order, elliptic, low-pass filter attenuates harmonics generated in the power amplifier. The capacitors for the filter are circuit board pads.The reflectometer uses printed circuit board traces for micro-strip transmission lines. Transmission line segments (with an impedance of about 82 ohms) on either side of a 50 ohm... [ more ]
