Question

You are asked to design an end-fire array using two quarter-wave vertical antennas that are separated by a half wavelength. Two separate coaxial cables with VF = 0.65 are used to connect the transmitter to each antenna, and the operating frequency is 7.5 MHz. If the first antenna is driven with a length of coax that is 50 meters in length, what is the required length of the second transmission line in meters?a) length of first line in wavelengthsb) length of second line in wavelengthsc) length of second line in meters

Answer 1

Step-by-step explanation:

Given that,

Two operating coaxial cable

Velocity factor VF = 0.65

Operating frequency f = 7.5MHz

Length of Coaxial cable 1

L = 50m

Let calculate the wavelength of the coaxial cable

Electrical wavelength of the transmission line is described as

λ = 983.6 × VF / f

where

λ = wavelength, in ft

f = frequency in MHz

VF = velocity factor.

Therefore,

λ = 983.6 × VF / f

λ = 983.6 × 0.65 / 75

λ = 8.52ft

Since it is a half wavelength then,

λ = 8.52/2

λ = 4.26ft

1ft = 0.305m

λ = 4.26ft = 4.26 × 0.305

λ = 1.3m

The actual length is given as

L = 150×VF/f

L = 150 × 0.65 / 75

L = 1.3m

Then, the actual transmission length is equal to length of the second line in wave lengths.

Option B is correct