Problems

1. In Fig. 11 it is shown that about 65 microwatts are delivered to New York. If no intermediate repeaters are used, calculate the power that must be delivered to the line at San Francisco to supply this power to New York. Compare this with the total amount of power added along the line as shown in Fig. 11. If the characteristic impedance is 600-ohms resistance, calculate the input voltage and current for the first condition.

2. Assume that a 19-gauge cable with H-44-S loading extends from San Francisco to New York. If no repeaters are used, what power must be delivered to the cable at San Francisco to deliver 65 milliwatts to New York? If repeaters are used every 50 miles, what total power must be added to deliver 65 microwatts at New York? Assume that the input impedance of the loaded cable is about 820 ohms pure resistance, and calculate the input voltage and current for the first condition.

3. A non-pole pair side circuit of a 165-mil open-wire line is 1000 miles long. If the average daily attenuation change due to temperature variations is 5 per cent, what is the change in decibels? Calculate the corresponding change in decibels for a 19-gauge aerial cable with H-44-S loading. Of what practical significance are these figures?

4. On page 421 it is stated that the balanced modulator eliminates the carrier. Prove this to be true mathematically.

5. Make the substitution suggested on page 424 to prove that sidebands are created in the copper oxide bridge modulator.

6. Use a method similar to that employed in Fig. 24 to determine the output current wave shape when the carrier and sidebands are transmitted as in the type G carrier telephone system.

7. Calculate the characteristic impedance of the early coaxial cable. Do the dimensions used give the correct ratio (page 434) for minimum attenuation? If this same ratio is used for the 0.375-inch coaxial cable, what will be the nearest wire size used for the center conductor? Is this the size actually used?