Receiver Principles Flashcards
(21 cards)
What do receivers vary in?
Complexity.
Define a receiver.
A receiver converts electromagnetic energy into usable energy and outputs a reproduction of the original signal.
What are the three main REQUIREMENTS of an efficient receiver?
(S) SELECT the desired signal.
(E) EXTRACT the intelligence.
(P) PRODUCE sufficient power to operate the transducer.
What are the four main receiver characteristics?
(S) SENSITIVITY
(S) SELECTIVITY
(S) STABILITY
(N) NOISE
What are the three types of distinct frequencies to a receiver?
RF or Radio Frequency
IF or Intermediate Frequency
AF or Audio Frequency
What is the method used to produce an AF frequency?
Heterodyning.
Define Heterodyning
The generation of new frequencies by mixing, or multiplying, two waveforms
Define a filter.
A device which passes certain frequencies and rejects others.
Name the five filtering terms or ranges, and what frequencies do they allow.
Low Pass - All below a freq High Pass - All above a freq Band-Pass - All freq within a range Band Reject - All freq outside a range Notch - A very narrow band reject
What are the two types of filter bands? Define.
Passband - Frequencies allowed
Stopband - Frequencies rejected
Define gain
The ratio of output to input power, usually measured in Decibels (dB)
Expand AGC.
Automatic Gain Control
Define AGC
A system that automatically varies the receiver gain to maintain a reasonably constant output level
Why is this not advised for signals such as morse?
It will lower the dits and dahs and raise the breaks, preventing the signal.
What signals is AGC ideal for? Give an example.
Signals with a constant power output, such as AM
In AGC, what are the two factors it uses to operate?
Attack Time
Decay Time
Define attack time.
The time taken for AGC to respond to variations
Define decay time.
The time for AGC to stop responding to variations
What are the AGC attack times?
Short - 20mS
Medium - 100mS
Long - 200mS
What are the decay times?
200mS and above
Define Squelch.
A function that raises the noise floor to ignore interference (noise) but to allow the higher amplitude signal through.
