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LI NEAR
NON-LINEAR
Radio Amateurs
Referencelibrary
of Maps and Atl as
,.
OUT
Fig. 6. Here we have linear and nonlinear
amplifiers com pared, with triangular signal waveforms
instead of sine waves to make life easier fo r
our illustrators and bring out the differences
which are not o bvious wit h sine waves. Linear
amp lifier, left, faithfully reproduces input signal
at ou tput. Nonlinear am plifier, right, puts bend s
into the straight sides of th e waveform . These
bends represent second-harm onic distortion. In
general, any distor tion is described as "nonlinear"
operation.
hi-fi amplifier is linear, for instance, even
though it does have some small percent
distortion. In sp eaking of rf amplifiers for
modulated signals, t he distortion is measure
d wit h respect to the modulation
rather than the individual rf cy cles, and so
a linear rf amp lifier is one whic h does not
dist ort the modulation rather than one
which does no t distort the indi vidual cycles
of the input signal.
The linear/nonlinear classificati on helps
us to list the ways in whic h class A, B, and
C am plifiers are used . F or instan ce, almost
all linear audio amp lifiers operate in class
A, which squares with the " amateur"
definition of class A as being a linear
amp lifier. Many rf linears .at low po wer
levels also operate class A, an d in general
the class A operation is used almost exclusively
when very low distortion is required.
Most receiver circ uit s are class A.
Class AB and B amplifiers are widely
used to produce mo derate power levels
wit h limi ted dist ortion . The output stages
of many public-address amplifiers and almost
all hi-fi power stages operate in class
AB, and almo st all SSB fina l linear am plifiers
run as eit her class AB or B. In add ition
class B amplifiers are sometimes used in
,.
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RA DIO A MATEURS MAP OF NORTH AMERICA! Full
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WORLD ATLAS - On ly at las co mpi led for ra dio a rnet
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_ a com plet e set of maps o f t he world. 20 pa ge s.
size 8 31." x 12 " .. pos tpaid $2.00
Complete reference libr ary of maps - set of 4 as li ste d
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