In article . com,
"K7ITM" writes:
I'm curious, what sorts of things do amateurs do that really need
better than a 1dB noise figure on 2 meters? I can understand it on
higher frequencies, but I'd have thought that galactic noise, at least,
would be a limiting factor on 2 meters.

Looking to be educated,

I also question (a little) the need for better than a true 1dB NF
when using a terrestrial antenna in the 2M band. On the other hand,
if the transistor is speced to be able to supply 1dB NF, but isn't
working as well as desired because of preamp design, high return
loss, etc.

It isn't really HARD to get 1dB NF at frequencies
below 1GHz (or even higher), but it is sometimes tricky to get a good real
world NF while also providing good return losses (good impedance match),
at high signal levels, especially while trying to minimize DC power usage.

My own high-end jelly bean for near-ultimate performance below 1GHz,
moderately high power for reception (10mw - 100mw), reasonable noise match in
the 50-75Ohm range, but perhaps a little tricky due to high frequency
behavior would be the HP f54143 (Hi IP3, reasonable noise match, it has
lots/too much of UHF or higher freq gain, but is moderately well behaved).
This part costs less than $2... (I bought my supply for between
$1.50 and $2.00 each.) I'd also consider using moderate current SiGe
transistors while biasing them at about 10ma to 20ma (which is generally a
reasonable range for a good 50-75ohm noise match.) Either the SiGe
transistors NESG2101 or the PHEMT (54143) will give better than 1dB NF
with a generally fairly wide noise match. (SiGe is generally better than
most alternatives for oscillators -- off subject -- also, due to their
generally very good 1/f characteristics and generally high Beta, which
translates to generally low current noise -- esp in the low freqs where
part of the AM/PM noise comes from.)

Given the very wide signal strength range, I'd definitely consider OIP3
of at least 25-30dBm, and try to design for no more than 10-15dB gain.
It is very possible that even a very highly performing preamp will work
worse than no preamp at all!!!

John