Secure Comms Flashcards
Interception of communications is used to?
Gain information on enemy operations
Study the operating techniques of the enemy
Detect enemy positions
Enable false information to be fed to an enemy
Name two criteria used to determine that a system is a true spread spectrum
The transmitted bandwidth is much greater than the bandwidth of the information being sent
Something other than the modulating signal determines the bandwidth
A spread spectrum transmission offers three main advantages over a fixed frequency transmission, these are?
Resistant to noise and interference.
Difficult to intercept.
Spread spectrum transmissions can share a frequency band with many types of conventional transmissions with
minimal interference.
Explain the principles of Frequency Hopping Spread Spectrum
Transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudo random sequence known to both transmitter and receiver.
The squence used by Havequick radios is controlled by the Word of Day (WOD).
Time of Day is to ensure that for two radios communicate, they change frequency at the same time
Explain the operation of a direct sequence spread spectrum transmitter.
The information to be transmitted is converted to a digital signal.
The output of A/D convertor is combined with a Pesudo random code.
The modified signal is then mixed with the carrier this will distribute the RF signal over a large bandwidth.
The signal is then amplified ready for transmission
What is the purpose of the Word of the day
Determines the frequency hopping pattern
What is the time of the day
Synchronises transmitter and receiver
Explain Direct sequence spread spectrum
The signal is mixed with a pseudo random code
The output signal is spread over a wide bandwidth and hidden in the noise
