FM Radio Station Mute Function Part 14

Radio Station mute function schematic

FM RADIO STATION MUTE FUNCTION PART 14

This circuit shows details for adding a mute function to the FM radio station. A switch will mute the microphone. When muted, the LED will stay lit.


Microphone Mute Function with LED monitor
When the DPDT switch is in a normalized position, the electret microphone is active, the LED is not connected, and broadcast takes place. When switched, the microphone cuts out, resistor R2 is connected to replace the microphone, and the LED lights. A carrier signal continues to broadcast but there is no sound. The LED is on a separate circuit and does not interfere with the microphone. The microphone resistance is measured at 1.37 ohms (when not in the circuit).

Note: On the schematic, replace the text SPDT with DPDT.

http://humanoidolabs.blogspot.tw/2013/12/fm-radio-station-controls.html

FM Radio Station Part 5 Index
http://humanoidolabs.blogspot.tw/2013/12/fm-radio-station-part-5-index.html 

FM Radio Station Testing Part 7

The 9-volt powered mini radio station is set to broadcast on the FM band near 102 MHz with more tests using a tiny 1.75-inch circular loop antenna. Today's tests include a harmonic and range study, along with orientation reviews. A very sensitive Chinese multi band radio is at the receiving end. The photo does not show the actual test range distance. In this second day "on the air" test, a small script will be sent out over the "air waves." Stay tuned to this project and the radio station just keeps growing and growing.

FM RADIO STATION TRANSMITTER TESTING PART 7
The next phase of the radio station is testing and calibration of the transmitter and equipment, and running more experiments to pace the radio station and see what works best.

* Range
* Transmitter Signature Footprint
* Detail & Extent of Harmonics
* Quality with Microphone
* Background Pickup Determination
* Orientation Positioning Effects
* Results of interchangeable Antenna
* Results with Different Antenna Designs 
* Signature of Transmissions with Antenna Position
* Effects of Antenna Blockage
* Types of Material and the Effects on Wireless
* Results of Direct Audio Feed Bypassing Mic
* Results of Varied Lower Power Voltage
* Instrumentation Add On 
* Mute Circuit Resistor Determination 
* Power Determinations

FM Radio Station Part 5 Index
http://humanoidolabs.blogspot.tw/2013/12/fm-radio-station-part-5-index.html