How can intermodulation interference between two transmitters in close proximity often be reduced or eliminated?

By installing a terminated circulator or ferrite isolator in the feed line to the transmitter and duplexer.

Intermodulation happens when there is a nonlinear combining of at least two input signals into a one, and is considered a distortion

See Wikipedia's article on Intermodulation

See the Lifewire site for the article What Is Intermodulation Distortion (IMD)? By Gary Altunian

See RF Page site for the article How does Intermodulation Distortion occur

To deal with intermodulation, limit the use of amplifiers to the linear range, and reduce any non-linear components.

See the Softwright site for the article Finding, Solving, and Preventing Intermodulation Problems

See the Anritsu site for the article Passive Intermodulation (PIM)

Last edited by markadlerdallas. Register to edit

Tags: none

How can parasitic oscillations be eliminated in a power amplifier?

By neutralization.

Neutralization is where by feeding a 180-degree out-of-phase portion of the output back to the input.

With premise that combining two signals together out of phase by 180 degrees causes them to cancel AND that the correct answer here has 180 degree out-of-phase in it we can conclude "By feeding a 180-degree out-of-phase portion of the output back to the input" is the correct answer.

See Wikipedia's article on Parasitic oscillation

Last edited by kd7bbc. Register to edit

Tags: none

What is the name of the condition that occurs

• when the signals of two transmitters in close proximity mix together in one or both of their final amplifiers, and

• unwanted signals at the sum and difference frequencies of the original transmissions are generated?

Intermodulation interference.

Intermodulation happens when there is a nonlinear combining of at least two input signals into a one, and is considered a distortion

See Wikipedia's article on Intermodulation

See the Lifewire site for the article What Is Intermodulation Distortion (IMD)? By Gary Altunian

See RF Page site for the article How does Intermodulation Distortion occur

To deal with intermodulation, limit the use of amplifiers to the linear range, and reduce any non-linear components.

See the Softwright site for the article Finding, Solving, and Preventing Intermodulation Problems

See the Anritsu site for the article Passive Intermodulation (PIM)

Last edited by markadlerdallas. Register to edit

Tags: none

What term describes a wide-bandwidth communications system in which the RF carrier varies according to some predetermined sequence?

Spread-spectrum communication.

This is a radio communication that uses different frequencies, sometimes called frequency hopping. It helps to expand the bandwidth for the signal.

See Wikipedia's article on Spread spectrum

Also, see the Maximintegrated site for the article INTRODUCTION TO SPREAD-SPECTRUM COMMUNICATIONS

Last edited by markadlerdallas. Register to edit

Tags: none

How can even-order harmonics be reduced or prevented in transmitter amplifier design?

By using a push-pull amplifier.

As a transistor pushes electrons (amperes) forward, another transistor will pull in a different direction. The push-pull transistors each act for half of the signal cycle, with one on the positive side, and the other on the negative one.

The push is supplying the amperes while the pull is taking away from the pushed amperes. Generally, this type of amplifier is often the Class B or A, using a push-pull signal, with each 180° of the cycle.

See Wikipedia's article on Push–pull output

Also, see the Wat Electronics site for the article Push-Pull Amplifiers Circuit Diagram, Working and Applications

Last edited by markadlerdallas. Register to edit

Tags: none

What is the modulation type that can be a frequency hopping of one carrier or multiple simultaneous carriers?

Spread spectrum.

This is a radio communication that uses different frequencies, sometimes called frequency hopping. It helps to expand the bandwidth for the signal.

See Wikipedia's article on Spread spectrum

Also, see the Maximintegrated site for the article INTRODUCTION TO SPREAD-SPECTRUM COMMUNICATIONS

Last edited by markadlerdallas. Register to edit

Tags: none