105 Hard Study (Signals)

PRF (Pulse Repetition Frequency) 

The rate at which pulses are transmitted, given in hertz or pulses per second. Reciprocal of pulse - repetition time. 

Cycle

One complete wave motion, typically measured from crest to crest or trough to trough 

Solar Flares 

Intense burst of radiation from the Sun 

FM (Frequency Modulation) 

The variation of the instantaneous frequency of the carrier, either above or below the frequency 

CW (Curve Width) 

The width of the pulse arc 

True Bearing 

The angle between true north and a  line pointed directly at the target 

Fading 

The variation in signal strength due to changes in the transmission path 

PW (Pulse Width) 

The duration of the pulse. 

Semi-Duplex 

Similar to half duplex but typically implies automatic switching between transmit and receive modes. 

Elevation Angle 

Used by height finding radars, uses a very narrow beam in both horizontal and vertical search planes. 

Azimuth Angle 

Angular measurement in the horizontal plane in a clockwise direction. 

Continuous Wave

Modulation by on/off keying—Morse code. (Can also be Carrier Wave - which carries multiple frequencies over one channel.) 

Beam Width (BW) 

Angular width of the beam's curvature. 

Attenuation

The loss of signal strength as a wave travels through a medium. 

Refraction

The changing of direction of a wave as it leaves one medium and enters another medium of different density. 

Diffraction

The bending or spreading of waves around obstacles or through openings.