A 50 MHz sky wave takes 4.04 ms to reach a receiver via re-transmission from a satellite 600 km above earth’s surface. Assuming re-transmission time by satellite negligible, find the distance between source and receiver. If communication between the two was to be done by Line of Sight (LOS) method, what should size and placement of receiving and transmitting antenna be?

An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of (R) and (C) as
(ii) (R = 10 \text{ k}\Omega), (C = 0.01\mu\text{F}).

An amplitude modulated wave is as shown in Fig. 15.4. Calculate (iii) peak value of information voltage.

An amplitude modulated wave is as shown in Fig. 15.4. Calculate (ii) peak carrier voltage and,

(iii) Extrapolate and predict the problems one can expect if more waves are to be modulated.

(ii) Is the plot symmetrical about $\omega_c$? Comment especially about plot in region $\omega < \omega_c$.

An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of (R) and (C) as
(iii) (R = 10 \text{ k}\Omega), (C = 0.1\mu\text{F}).

(i) The intensity of a light pulse travelling along a communication channel decreases exponentially with distance x according to the relation (I = I_{o}e^{-\alpha x}), where (I_{o}) is the intensity at (x = 0) and (\alpha) is the attenuation constant.
Show that the intensity reduces by 75 per cent after a distance of (\frac{\ln 4}{\alpha})

(iii) Extrapolate and predict the problems one can expect if more waves are to be modulated.

(ii) Is the plot symmetrical about (\omega_{c})? Comment especially about plot in region (\omega < \omega_{c}).

(iv) Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?

An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of $R$ and $C$ as (iii) $R = 10 \text{ k}\Omega$, $C = 0.1\mu\text{F}$.

(ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation (\text{dB} =10 \log_{10}(\frac{I}{I_{o}})). What is the attenuation in dB/km for an optical fibre in which the intensity falls by 50 per cent over a distance of 50 km?

(iv) Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?

An amplitude modulated wave is as shown in Fig. 15.4. Calculate (ii) peak carrier voltage and,

(i) The intensity of a light pulse travelling along a communication channel decreases exponentially with distance $x$ according to the relation $I = I_o e^{-\alpha x}$, where $I_o$ is the intensity at $x = 0$ and $\alpha$ is the attenuation constant. Show that the intensity reduces by 75 per cent after a distance of $\frac{\ln 4}{\alpha}$

(ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation $\text{dB} = 10 \log_{10} \frac{I_o}{I}$. What is the attenuation in dB/km for an optical fibre in which the intensity falls by 50 per cent over a distance of 50 km?

(i) Draw the plot of amplitude versus ‘$\omega$’ for an amplitude modulated wave whose carrier wave ($\omega_c$) is carrying two modulating signals, $\omega_1$ and $\omega_2$ ($\omega_2 > \omega_1$).

An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of (R) and (C) as
(i) (R = 1 \text{ k}\Omega), (C = 0.01\mu\text{F}).

An amplitude modulated wave is as shown in Fig. 15.4. Calculate (iii) peak value of information voltage.