Question 6
(a). State:
(i). two radio frequency bands;
(ii). the frequency range for each of the bands in 6(a)(i).
(b). List three applications of amplitude modulation.
(c). State the frequency in the output of the mixer stage of an a.m superheterodyne receiver.
Observation
The expected answers were;
(a)Radio frequencies
(i) (ii)
Medium frequency (300 – 3000kHz)
High frequency (3 – 30MHz)
Very high frequency
(30 – 300MHz)
(b). Applications of A.M. Signal
(i). Used for analogue telephony
(ii). Broadcasting in short and medium wave bands
(iii). For video signals in T.V. transmission
(iv). SSB radio
(c). Frequency in the output of the mixer stage of an a.m. superheterodyne receiver
(i). Sum frequency
(ii). Difference frequency
(iii). Local oscillator frequency
(iv). Radio frequency
The term radio frequency refers to those frequencies utilized for wireless communications extending from HF to EHF. However, everyday usage confuses the electromagnetic spectrum (with ELF at the lower end) with radio frequencies. Only a few candidates gave correct responses to this question.