The audio power of the human voice is concentrated at about 300 Hz. Antennas of the appropriate size for this frequency are impracticably large, so that to send voice by radio the voice signal must be used to modulate a higher (carrier) frequency for which the natural antenna size is smaller. a. What is the length of an antenna one-half wavelength long for sending radio at 300 Hz

the length of an antenna one-half wavelength long for sending radio at 300 Hz is 500 km

Explanation:

Given the data in the question;

we know that wave length is;

λ = c/f

c is the speed of voice ( 3 × 10⁸  m/s )

frequency f = 300 Hz

so we substitute

λ = 3 × 10⁸ / 300

λ = 1000000 m

we know that; 1 km = 1000 m

so

λ = 1000000 m / 1000

λ = 1000 km

hence, an antenna one-half wavelength will be;

λ /2

=  1000 km / 2

= 500 km

Therefore, the length of an antenna one-half wavelength long for sending radio at 300 Hz is 500 km