Question

(a) Describe briefly the three factors which justify the need for translating a low frequency signal into high frequencies before transmission.

(b) Figure shows a block diagram of a detector for AM signal.

Draw the wave forms for the 

(i) input AM wave at A,

(ii) output B at the rectifier, and 

(iii) output signal at C.

Answer 1

(a) There are three factors :

(i) Wider Band width : High frequency provide wider bandwidth.

(ii) Distance : High frequency wave used to carry baseband signals (low frequency signal) over a distance of several thousand kilo metres.

(iii) Cost : High frequency transmits with low cosf. 

(b) (i) Input AM wave at A

(ii) Output B at the rectifier

(iii) Output signal at C