– The very first amplification stage in a radio frequency
receiver. Usually this
stage has limited filtering and can be sensitive to energy far
removed from the desired receive frequency.
This stage is greatly responsible for the basic receiver
sensitivity and can be overloaded with very strong signals fairly
easily. It is usually a
non-linear amplifier by design.
– When used with radio frequency amplifiers, the term refers to
the inability of an RF amplifier to increase the strength or level
of radio energy without distorting or changing the energy waveform
in some way. For
example, if you turn up an audio amp too much the audio often begins
to sound different or distort.
This is because the audio amplifier is non-linear at high
power demands. In an RF
amplifier, this non-linearity causes harmonic and intermodulation
distortion. This is the creation of RF energy at frequencies not
originally present in the non-amplified RF waveform.
Distortion -- The
non-linear amplifier effect of creating sums and differences signals
from multiple signals present in the amplifier.
For example, suppose a signals of 150 MHz
and 155 MHz are present in a non-linear amplifier.
Then these signals would mix and create new signals of
(155-150)+155 or 160 MHz and/or 160+150 or 310 Mhz and so on.
If any of these non-linear signal products lands near the
desired receive frequency, then interference occurs within the
receiver. Since most
two-way communications type amplifiers are non-linear,
communications systems are designed to avoid receiving
intermodulation created signals.
Cell: (301) 785-6716
Call your local
radio dealer, USMSS, or RF Consultant for your
interference resolution needs.