XM Radio: Understanding How Radio Waves are Generated
- Date: 2007-07-01 - Word Count: 544
Share This!
There are two types of devices in which it may be necessary to generate amplitude modulation. The first of these is, the amplitude modulation transmitter generates such high power that its prime requirement is efficiency, so quite complex means of amplitude modulation generation may be used. The other device is the amplitude modulation generator. Here the amplitude modulation is produced at such a low power level that the simplicity is a more important requirement than efficiency. Although the methods of generating amplitude modulation can be different but generating high power are always taken care of.
In order to generate amplitude modulation wave it is necessary merely to apply the series of current pulses to a tuned circuit. Each pulse, if it were the only one, would initiate a damped oscillation in the tuned circuit. The oscillation would have initial amplitude proportional to the size of the current pulse and a decay rate dependent on the time constant of the circuit. Since a train of pulses is fed to the tank circuit here, each pulse will cause a complete sine wave proportional in amplitude to the size of this pulse. This will be followed by the next sine wave proportional to the size of the next applied pulse and so on. Bearing in mind that at least ten times as many pulses per audio cycle are fed to a practical circuit we see that an extremely good approximation of an amplitude modulated wave will result if the original current pulses are made proportional to the modulating voltage. The process is known as the flywheel effect of the tuned circuit, and it works best with a tuned circuit whose operating point is not too low.
It is possible to make the output current of a class C amplifier proportional to the modulating voltage by applying this voltage in series with any of the direct current supply voltages for this amplifier. Accordingly cathode or emitter, grid or base and anode modulation of class c amplifiers are all possible, as is any combination of these methods. Each has its own applications, advantages and drawbacks.
In an amplitude modulation transmitter, amplitude modulation can be generated at any point after the radio frequency source. As a matter of fact even a crystal oscillator could be amplitude modulated, except that this would be an unnecessary interference with its frequency stability. If the output stage in a transmitter is plate modulated the system is called high level modulation. If the modulation is applied at any other point, including some electrode of the output amplifier, then so called low level modulation is produced. Naturally the end product of both systems is the same but the transmitter circuit arrangements are different.
It is not feasible to use plate modulation of the output stage in a television transmitter, because of the difficulty of generating high video powers at a large bandwidth required. Grid modulation of the output stage is the highest level of the modulation employed in television transmitters. It is called high level modulation in television broadcasting and any thing else is then called low level modulation.
--
Tymon Hytem has worked in the electronics feild for the past 15 years. He enjoys helping people decide on electronic gadgets from telephones to XM Radio and choosing the perfect xm radio, xm satellite radio
Your Article Search Directory : Find in Articles
© The article above is copyrighted by it's author. You're allowed to distribute this work according to the Creative Commons Attribution-NoDerivs license.
In order to generate amplitude modulation wave it is necessary merely to apply the series of current pulses to a tuned circuit. Each pulse, if it were the only one, would initiate a damped oscillation in the tuned circuit. The oscillation would have initial amplitude proportional to the size of the current pulse and a decay rate dependent on the time constant of the circuit. Since a train of pulses is fed to the tank circuit here, each pulse will cause a complete sine wave proportional in amplitude to the size of this pulse. This will be followed by the next sine wave proportional to the size of the next applied pulse and so on. Bearing in mind that at least ten times as many pulses per audio cycle are fed to a practical circuit we see that an extremely good approximation of an amplitude modulated wave will result if the original current pulses are made proportional to the modulating voltage. The process is known as the flywheel effect of the tuned circuit, and it works best with a tuned circuit whose operating point is not too low.
It is possible to make the output current of a class C amplifier proportional to the modulating voltage by applying this voltage in series with any of the direct current supply voltages for this amplifier. Accordingly cathode or emitter, grid or base and anode modulation of class c amplifiers are all possible, as is any combination of these methods. Each has its own applications, advantages and drawbacks.
In an amplitude modulation transmitter, amplitude modulation can be generated at any point after the radio frequency source. As a matter of fact even a crystal oscillator could be amplitude modulated, except that this would be an unnecessary interference with its frequency stability. If the output stage in a transmitter is plate modulated the system is called high level modulation. If the modulation is applied at any other point, including some electrode of the output amplifier, then so called low level modulation is produced. Naturally the end product of both systems is the same but the transmitter circuit arrangements are different.
It is not feasible to use plate modulation of the output stage in a television transmitter, because of the difficulty of generating high video powers at a large bandwidth required. Grid modulation of the output stage is the highest level of the modulation employed in television transmitters. It is called high level modulation in television broadcasting and any thing else is then called low level modulation.
--
Tymon Hytem has worked in the electronics feild for the past 15 years. He enjoys helping people decide on electronic gadgets from telephones to XM Radio and choosing the perfect xm radio, xm satellite radio
Your Article Search Directory : Find in Articles
Recent articles in this category:
- Canadiens Early Season Struggles
Inconsistency has reared its ugly head once again. After a shutout loss to the lowly New Jersey Devi - Mens Magazine in the Toronto Market
Magazines are wonderful things. They are able to explore their particular area of interest in more d - They Won the Lottery But Then Lost it All
We all dream about winning the lottery and every time we watch those balls spin we think about what - Manchester City Imploding
Life changed for Manchester City fans the minute their club was taken over by the ultra wealthy Oil - Different Types of Sports Water Bottle
If you are an athlete and there is a competition the next day, there are a lot of things to prepare. - Poker Supplies a Person Needs to Play
There are a lot of people all over the world that enjoy playing poker on a regular basis. There are - Data on NCAA Football 11 (XBox)
EA Sports has always been the pinnacle for sports video games. The Madden franchise for NFL football - World Golf Amateur Team Championship 2012
Golf is said to be the game of nobles. Over a period of time, the game has developed into a craze fo - Will "The Decision" Yield the Result? Lakers, Heat Seen as Likely Finalists
By far the biggest moment in the NBA offseason was the hour-long ESPN special in which LeBron James - The Evolution of the Game: Table Tennis
Table tennis was probably derived from the game "Royal Tennis," a popular diversion during medieval
Most viewed articles in this category:
- Rainbow, Brown And Brook Trout
Maine fishing has Rainbow, Brown, and Brook trout. Trout are an important part of fishing tradition. - Gymnastics Floor Music
Over the last decade or two, gymnastics as a sport has undergone considerable changes in the way it - Texas Holdem Blinds - Understanding Blinds In Texas Hold'em Poker
Posting blinds is a very important aspect of the betting structure of Texas Hold'em poker. It keeps - Indoor Mobility Scooters
Mobility scooters exclusively provide assistance to physically disabled people, who don't necessaril - Texas Holdem Tournament - Learn How To Run A Texas Hold'em Tournament
Texas Hold'em is a popular game, so next time you consider hosting a social function at your house w - The Nfl Channel And The Controversy Surrounding It
If you watch TV, and especially if you are a loyal spectator of the NFL Channel, you might have hear - Texas Holdem - How To Become Better At Texas Hold'em Poker
If you know the rules, if you know the game, if you know the odds, chances are you'll do well at pok - Essential Boxing Equipment For Every Boxer
When you are training to become a boxer there are a few very important pieces of boxing equipment th - Some Advice On How To Stay Motivated To Run
Staying Motivated to Run Do you have a hard time staying motivated to run? There are a lot of thing - NCAA: Three Good Coaches
There are coaches in each and every type of sport out there, and many of them are good at what they
