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A radio network is set up with 50 mobile transmit-receive units and a central hub station.The network has ten RF channels for transmissions to the mobile units and ten RF channels for transmissions from the mobile units to the central hub. The network operates in the uhf band.The hub station allocates frequencies to the mobile units when a radio link is established.

a. The 50 mobile units share the ten RF channels. The RF channels have a bandwidth of 30 kHz. Modulation is FM with analog voice signals. Is this a FDM or FDMA system? Does it have fixed access or demand access?

b. One channel is reserved for random access: Why?

c. The network is used for voice communications. Is it possible for one mobile unit to connect to another mobile unit directly? What advantage is there in connecting through the hub?

d. Occasionally the hub has a voice message that is to be sent to all the mobile units. Can the message be sent on a single RF frequency?

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#### Solution Preview

a.
The mobile system share the frequency limited carrier frequency resource so it is an FDMA system. Further carrier frequencies are only allocated from the management system via the hub as required by mobiles when they want to communicate. As such this is also defined as a demand access system.

b.
One channel reserved for random access for emergency service communication and for broadcast to all ...

#### Solution Summary

The analog voice signals for radio networks are examined.

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## Radio Tuning Circuit

A Radio Tuning Circuit
A radio can be tuned into a particular station frequency by adjusting the capacitance in an L-C circuit. Suppose that the minimum capacitance of a variable capacitor in a radio is 4.18 .
Part A
What is the inductance of a coil connected to this capacitor if the oscillation frequency of the L-C circuit is 1.50 , corresponding to one end of the AM radio broadcast band, when the capacitor is set to its minimum capacitance?
Hint A.1 Frequency of an L-C circuit
Hint not displayed
Hint A.2 Angular frequency and cycles per second
Hint not displayed
Express your answer in henrys to three significant figures.