A radio communication system transmits a radio frequency signal and depends on a substantial amount of that signal being received at the receiver. Now we are going to take a closer look at that problems interference causes in TV and FM radio systems since we all can identify with these. We will also discuss some methods of Troubleshooting of TV and FM Radio System used to resolve interference problems. After completing this section, you will be able to: Identify different types of interference Describe three methods to reduce interference Troubleshoot…
Read MoreReactance Modulator Circuit Operation and Troubleshooting
The reactance is efficient and provides a large deviation. It is popular and used often in FM transmitters. Figure 1 illustrates a typical reactance modulator circuit. Refer to this figure throughout the following discussion. The circuit consist of the reactance circuit and the master oscillator. The reactance circuit operates on the master oscillator to cause its resonance frequency to shift down depending on the modulating signal being applied. The reactance circuit appears capacitive in nature to the master oscillator. In this case, the reactance looks like a variable capacitor in…
Read MoreTroubleshooting of FM transmitter
The most likely types of FM radio a technician will be called to service are an automotive mobile, a fixed base station, or a hand-held portable. Either the mobile or the fixed base station can have power outputs as high as 150 W. Some of these transmitters can be damaged if not operated into the proper load impedance, usually 50-ohm. Some contain automatic circuitry to shut the transmitter off it is not connected to a proper load. Dummy loads are made for this purpose, so make sure you have one…
Read MoreArduino Based Automatic Call Answering Machine
The project “Arduino and GSM Based Automatic Answering Machine” is designed to answer the phone call with prerecorded message when we are unable to attain call. Sometime in this busy world we might not be able to attain the phone call due to several reasons (generally when we are in bathroom or watching movie in cinema or forget mobile in home). These calls might be important i.e. call might be from office or business call which cannot be ignored. Thus, the project posted here receive the call after three rings…
Read MoreRegulated Power Supply Troubleshooting
If the system is completely dead, that is nothing happens in the system, you should immediately suspect the power supply. This is one part of any system where the average technician can often find and repair a problem. Any system is powered by battery or a transformer-rectifier supply connected to the 220-V lines. Batteries usually power portable system. A 9-V battery is most common. To check its output voltage, turn the system on (to load the battery) and measure the battery’s terminal voltage. If it is significantly below 9V, perhaps…
Read More10 Level Battery Charge Indicator Circuit
We already indicates state of battery using battery status indicator circuit and battery voltage state indicator using 741 IC, this time we indicate battery status in 10 different levels. The project “10 Level Battery Charge Indicator Circuit” is designed using comparator IC LM3914, used to indicates charge of battery in 10 different level. The project uses 10 LEDs to indicate the charge of battery in 10 level i.e. each glowing LED indicates 10% of charge in battery. Let say, if seven LEDs glow, the charge available in battery is 70%. It…
Read MoreTroubleshooting of AM Converter Circuit
In this section we are going to analyze and troubleshoot the AM converter circuit. the converter, also known as autodyne circuit, is a combination of the local oscillator and the mixer in a single stage. We are also going to discuss the power supply and audio amplifier problems in this section Upon completing this section, you should be able to Troubleshoot an AM converter circuit Identify an open input circuit Identify a dead or intermittent local oscillator circuit Identify causes for a dead and intermittent local oscillator Troubleshoot the receiver’s…
Read MoreCCTV Switcher Circuit using Timer IC 555
Here is a simple project CCTV Switcher circuit using timer IC 555 and decade counter IC 4017. The basic function of this project is to switch between different CCTV cameras sequentially i.e. one CCTV output is displayed on TV at a time. A CCTV (Closed Circuit Telephone) camera is used for video surveillance by using a video camera. Sometimes one CCTV camera is not sufficient for surveillance entire area thus we have to use multiple cameras to cover the entire area of surveillance. The circuit posted here control four CCTV…
Read MoreArduino and RFID based Door Access System
The project Arduino and RFID-based Door Access System is basically an access control system and can be placed where authorized entry is compulsion like office, school, etc. Previously in bestengineeringprojects.com, we had already posted RFID based security system using microcontroller AT89C52 which is used to open the door and Arduino and RFID Based Attendance Systems for taking attendance. Working of RFID Module | Arduino and RFID based Door Access System RFID (Radio Frequency identification) basically use an electromagnetic field to detect unique tag assigned to object in the vicinity. An RFID…
Read MoreAssembly Program to Find Vowel in String | 8086
Here is the program to find the number of vowel in string written in assembly language. This program display the number of vowels in string and also total number of string without vowel in a clear screen with reverse attributes Assembly Program to Find Vowel in String | 8086 //8086 PROGRAM F8-01A.ASM Program: .MODEL SMALL .STACK 64 .DATA MAXCHAR DB 60; ACTCHAR DB ?; STR DB 60 DUP (?); VOWEL_NO DB 0; NEWLN DB 0DH,0AH,”$”; CHECK STR DB 65, 69, 73, 79, 85, 97, 101, 105, 111, 117; {A, B,…
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