sjones wrote:
Hello All,
I was wondering what are the differences between a preamp, RF amp and
an LNA.

I was thinking they are all one and the same. Are there any subtle
differences among them for these names?

Thanks.

They all refer to amplifiers, and might be used interchangeably in some
cases.

A "preamp" is generally a low-level amplifier, and to be practical I'd
expect it would have reasonably low noise. Like the name suggests, it
goes at the front of a signal chain. It's a name used at RF, but also
for audio and even sub-audio work.

An RF amp presumably amplifies radio frequencies. That's a pretty
broad frequency range, and the particular amplifier might well be tuned
to a very narrow band, or optimized for some modest range of
frequencies (such as 140-150MHz). There's nothing in the name that
says it's low power. It could be an RF power amplifier, delivering
kilowatts of output. The term isn't very descriptive, but you could
add adjectives to narrow it down, like "a low-noise 2-meter mast
mounted receiver RF amp."

A LNA -- low noise amplifier -- generally refers to an RF preamp with
good to very good noise figure, commonly mounted at the antenna so as
to not degrade the system noise figure with the loss from a
transmission line. Because they are most useful at frequencies where
the atmospheric noise is low, you probably wouldn't find LNAs for use
at 4MHz, but they are very commonly used on dishes at microwave
frequencies. But again, there's nothing in the name that really tells
you the frequency range. The name could reasonably be adopted by audio
folk dealing with tiny signals from transducers like moving-coil phono
cartridges.

And of course, others may have slightly different (or even very
different) slants on the meanings.

Cheers,
Tom