Transmitting portion of a transmitter works

In summary, a pressure transmitter is used to ensure that a given level of safety is maintained in various types of situations.
  • #1
Aethaeon
4
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(Update -- please read the third post -- I guess I'm wondering how an antenna works in particular).Hey,

I can't seem to find much information on how the actually transmitting portion of a transmitter works -- how does one efficiently generate EM waves?

Thanks!(I'm aware that the rough idea is to accelerate charges back and forth at a particular frequency, what I want to know is how one actually goes about doing that)
 
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  • #2


Welcome to PF. Briefly, EM waves in the radio frequency band are generated using crystal oscillators or VFOs. The signal is then amplified to the desired power level and fed to the antenna through a matching network which matches the impedance of the amplifier to the impedance of the transmission line. Modulation of the signal depends on the mode (AM, FM, SSB etc...) You may find one or more of these books of interest:
http://www.arrl.org/catalog/index.php3?category=Help+for+Beginners [Broken]
 
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  • #3


Thanks for the reply, TurtleMeister.

I should clarify exactly what I was wondering --

Suppose I already have a signal that I want to transmit, and its already amplified, etc. How do I actually turn that signal into EM waves?

I guess, basically, I don't understand how to analyze how an antenna works. Since an antenna is conductive, so there's no potential across any parts of it -- why do electrons in the antenna oscillate?

If I hack apart a power cord to get a plug and two bare wires, I ground one and leave the other one free, and then plug it in, will I get strong EM waves at 60 Hz (outlet frequency)?
 
  • #4


The electrons oscillate in an antenna for the same reason they oscillate in an electric light bulb. They are forced to do so by the power source. However, that is where the similarity ends. The difference is in the frequency of oscillation.

The antenna may seem like an open circuit but it's not at rf frequencies. The reason has to do with the frequency and the length of the antenna. When a dipole antenna is excited with RF, electrons will flow back and forth at nearly the speed of light. When the antenna length matches the wavelength of the RF then the antenna will radiate with maximum efficiency. The length of the dipole can be determined by: l = 468,000,000 / f where l is the antenna length in feet and f is the frequency in hertz. The antenna is not an open circuit because the electrons never have time to travel farther than the wavelength of the frequency.

Aethaeon said:
If I hack apart a power cord to get a plug and two bare wires, I ground one and leave the other one free, and then plug it in, will I get strong EM waves at 60 Hz (outlet frequency)?
No. If you use the formula you will see that your power cord would need to be 7,800,000 feet long.

Edit: Actually, since you're grounding one side of the power cord it would be 3,900,000 feet for a quarter wave.
 
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  • #5


As a means of monitoring activity in a number of manufacturing facilities, marine research, and general production control, a pressure transmitter will not only help to ensure positive results; it also can be a great way of maintaining acceptable levels of safety.

1. a. An electronic device that generates and amplifies a carrier wave, modulates it with a meaningful signal derived from speech or other sources, and radiates the resulting signal from an antenna. b. The portion of a telephone that converts the incident sounds into electrical impulses that are conveyed to a remote receiver. c. A telegraphic sending instrument. 2. A neurotransmitter.
 

1. How does the transmitting portion of a transmitter work?

The transmitting portion of a transmitter is responsible for converting electrical signals into electromagnetic waves that can be transmitted through the air. This is achieved through a series of components such as an oscillator, amplifier, and antenna. The oscillator generates a high-frequency alternating current, which is then amplified to a higher power level. The amplified signal is then fed into the antenna, which radiates the electromagnetic waves into the air.

2. What is the purpose of the oscillator in the transmitting portion of a transmitter?

The oscillator in the transmitting portion of a transmitter is responsible for generating a high-frequency alternating current. This is important because the frequency of the electromagnetic waves determines the range and strength of the transmitted signal. Without the oscillator, the transmitter would not be able to produce the necessary frequency for transmission.

3. How does the amplifier in the transmitting portion of a transmitter work?

The amplifier in the transmitting portion of a transmitter takes the low-power signal from the oscillator and increases its power level. This is necessary because the signal needs to be strong enough to be transmitted over a long distance. The amplifier achieves this by increasing the amplitude of the signal, making it more powerful.

4. What role does the antenna play in the transmitting portion of a transmitter?

The antenna in the transmitting portion of a transmitter is responsible for converting the electrical signals into electromagnetic waves and radiating them into the air. The shape and size of the antenna determine the direction and strength of the transmitted signal. Different types of antennas are used for different purposes, such as directional antennas for long-distance transmission and omnidirectional antennas for short-range transmission.

5. How is the transmitted signal received by the receiver?

The transmitted signal is received by the receiver through its own antenna, which is tuned to the same frequency as the transmitter. The electromagnetic waves from the transmitter induce a current in the receiver's antenna, which is then amplified and processed to extract the original electrical signal. The receiver then converts this signal back into its original form, such as sound or video, for the user to receive and interpret.

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