LNA Technology FAQ,s

The answers to these frequently asked questions are written to be easily understood by persons with a wide range of technical expertise. Some of the answers are simplified, in order to keep the explanation understandable to users with limited technical knowledge. We encourage you to find out more about the various subjects! Search the Web, visit your local library, and investigate the various specifications and performance issues at your own level. Learning can be fun!

What is an LNA?
LNA stands for “Low Noise Amplifier”. This describes a class of amplifiers where the noise contribution, that is the noise produced by the amplifier is low, typically less than 1-3% of the amplifier gain in db. When utilized ahead of other gain stages, an LNA may be referred to as a preamplifier, or preamp.

What is RF Pollution / Congestion?
As more and more RF emitting devices are packed into the available spectrum, the amount of signals presented to your antenna and receiver front end becomes a significant limitation to system performance. Systems such as: paging, weather radio, aircraft, public service,
commercial communications, FM and Television broadcast, business band, and other users, all surround the VHF and UHF bands that Amateurs use.

On top of the above “authorized users” there are signals produced by computers, home
wireless networking systems, light dimmers, baby monitors, and other devices that may
produce “unauthorized” emissions in or near the Amateur bands.

When you add it all up, the front end of your receiver could be in trouble! No wonder you hear
all of those “Birdies” when you tune across the bands.

What is compression point, or P1db ?
In simple terms, the compression point of an amplifier is the point were it no longer will
produce the specified output increase, when the input is increased. This point is where the amplifier is just “running out of gas”. Not yet enough overloading to distort the signal (see IP3) but just at the point where the preamp begins to produce less gain than specified.

A simple way to think of this principle, is to use a home stereo system as an example.
At some point as you increase the volume, the output just won’t go any higher. If your home stereo amplifier is rated at 100 watts, don’t expect to get 150 clean distortion free watts from it!

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