Hobby Projects - Insulation tester, LED Circuits, Meters.
Showing posts with label Transmitter-Receiver. Show all posts
Showing posts with label Transmitter-Receiver. Show all posts

Monday, March 06, 2017

FM Remote Speaker System

A high quality, noise free, wireless FM transmitter/receiver may be made using the LM566 VCO and LM565 PLL Detector. The LM566 VCO is used to convert the program material into FM format, which is then transformer coupled to standard power lines. At the receiver end the material is detected from the power lines and demodulated by the LM565.

National Semiconductor Application Note 146 June 1975

The important difference between this carrier system and others is its excellent quality and freedom from noise. Whereas the ordinary wireless intercom uses an AM carrier and exhibits a poor signal-to-noise ratio (S/N), the system described here uses an FM carrier for inherent freedom from noise and a PLL detection system for additional noise rejection.

Carrier System Transmitter

Carrier System Transmitter
Two input terminals are provided so that both LEFT and RIGHT signals of a stereo set may be combined for mono transmission to a single remote speaker if desired. The input signal level is adjustable by R1 to prevent overmodulation of the carrier. Adding C2 across each input resistor R7 and R8 improves the frequency response to 20 kHz as shown inFigure 5. Although casual listening does not demand such performance, it could be desired in some circumstances.

Carrier System Receiver

Carrier System Receiver
The receiver amplifies, limits, and demodulates the received FM signal in the presence of line transient interference sometimes as high as several hundred volts peak. In addition, it provides audio mute in the absence of carrier and2.5W output to a speaker

Friday, June 03, 2016

Low Cost AM FM Stereo Receiver

This was a National Semiconductor Application Note, now TI. - Low Cost IC Stereo Receiver.

AN-147 Low Cost IC Stereo Receiver

Some Highlights

The LM3089 FM IF System does all the major functions necessary for FM processing, including a three stage amplifier/limiter and balanced product detector, as well as an audio preamplifier.

FM stereo demodulation is accomplished by the use of the LM1800 phase locked loop, thereby eliminating the need for external coils.

The AM function of the receiver is done completely with the LM3820 AM radio system. While designed for 3 section tuned superheterodyne application.

The LM382 dual preamplifier was selected for its minimum parts count and low noise capability.

Panel meters are employed in the FM system for both signal strength and center tuning, allowing for easy and accurate tuning. A directly driven LED offers immediate indication of FM stereo reception.

Low Cost AM FM Stereo Receiver

A single transistor tone control circuit was designed as the optimum cost/performance trade-off. The transistor is configured in a shunt-shunt feedback design, allowing gain variations between input functions.

The stereo power section, consisting of the LM378 dual audio amplifier, delivers 3W/channel with total harmonic distortion (THD) less than 1% and 4W/channel with THD less than 10%,

Saturday, February 02, 2008

PY2WM JK De Marco Projects

An Amateur Radio Enthusiast from Brazil. JK De Marco. In these pages Hams will find his ideas on QRP, Antennas and Complete circuits.

PY2WM JK De Marco Projects



A 40 dB RF Attenuator

"To measure power of a high power transmitter, or to be able to observe the output signal on an oscilloscope or spectrum analyzer, it is necessary that the signal is attenuated in accordance with the instrument, while it must be ensured that the transmitter is "seeing" the correct impedance. So it requires an attenuator that works with three ports (input, output, and output attenuated), all while maintaining the correct impedance of 50 ohms.

The circuit assembly and is shown here in EMRFD and also in the QST. When properly calibrated can be used for precision measurements in section 0-500 MHz, or a a calibration capacitor C1, can be used for the range of 0-50 MHz with reliability."

Other Projects and Ideas
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  • Simple ESR meter
  • Swr Power Measuring mW To KW
  • 5 Volts Reference Voltage Calibrator