In article .com,
K7ITM wrote:

Finally, can you think of a way to alter the amplifier's input
impedance in a way that does not degrade noise, so that you come closer
to an impedance match while maintaining a match for optimal noise?

Negative feedback increased input impedance. It looks like lossless
negative feedback will do this without also increasing the noise. Perhaps
use this to make the input impedance equal the noise-opt impedance- then you
can match the two together to the source (using a transformer or a tuned
circuit).

Here is a nice reference:

http://rfdesign.com/mag/radio_unique...tive_feedback/

The lossless feedback can be as simple as an inductor in the emitter or
source lead.

I've found lots of other references (mostly for-pay IEEE papers), it looks
like stability can be a big issue- no big surprise in a feedback network.

--
/* AB1GO */ /* Joseph H. Allen */
int a[1817];main(z,p,q,r){for(p=80;q+p-80;p-=2*a[p])for(z=9;z--q=3&(r=time(0)
+r*57)/7,q=q?q-1?q-2?1-p%79?-1:0%79-77?1:01659?79:0158?-79:0,q?!a[p+q*2
]?a[p+=a[p+=q]=q]=q:0:0;for(;q++-1817printf(q%79?"%c":"%c\n"," #"[!a[q-1]]);}