CBT RF Transmission & Antenna Systems

Question 1

What is the primary purpose of a transmission line in a broadcast RF system?

Accepted Answer

To transfer RF energy from the transmitter to the antenna with minimal loss

Answer

A transmission line's primary role is to efficiently transfer RF energy from the transmitter output to the antenna while minimizing losses due to reflection and attenuation.

Question 2

Which parameter describes the ratio of reflected wave voltage to incident wave voltage on a transmission line?

Accepted Answer

Voltage Reflection Coefficient (Γ)

Answer

The Voltage Reflection Coefficient (Γ) is the ratio of the reflected voltage to the incident voltage, and is the fundamental quantity from which SWR and return loss are derived.

Question 3

A broadcast FM antenna has a gain of 6 dBd. Approximately how many times greater is its effective radiated power compared to a dipole radiating the same transmitter power?

Accepted Answer

4 times

Answer

6 dBd corresponds to a power ratio of 10^(6/10) ≈ 4, meaning the antenna focuses energy to produce four times the ERP of a reference dipole.

Question 4

What is the standard characteristic impedance of most coaxial transmission lines used in broadcast RF systems?

Accepted Answer

50 ohms

Answer

50 ohms is the standard characteristic impedance for broadcast transmitter output and coaxial transmission lines, as it balances low loss and high power handling.

Question 5

What does VSWR of 1:1 indicate about a transmission line system?

Accepted Answer

The load is perfectly matched and no power is reflected

Answer

A VSWR of 1:1 indicates a perfect impedance match between the transmission line and the load, meaning zero reflected power and maximum power transfer to the antenna.

(CBT) Certified Broadcast Technologist Practice Test

(CBT) Certified Broadcast Technologist Practice Test

CBT RF Transmission & Antenna Systems