[Orion] V2.059d Vs. v1.373b5 Noise Reduction Code + My experiences with 1.373b5

[Bill Tippett]

K2XX:
 >I replaced 2.059d with 1.373b5 last night and the change in performance
was both dramatic and negative.    There was an enormous increase in RF
gain, which was further increased when invoking NR.  I tried
manipulating the Threshold, Decay, Attenuator and NR setting without
much improvement.  To make 40M CW even marginally listenable, I had to
use 12 dB of attenuation.  The NR seemed to act properly with the
attennuation.  The Threshold setting seemed to have no effect and there
seemed to be a non-linearity in the RF gain control.

         Almost certainly an indication RF GAIN is set too high.
Also, AGC Threshold and RF GAIN are now linked in all V1
versions following 1.371.  To set RF GAIN correctly:

1.  Set AGC Threshold = 1 uV for all bands, all AGC options.  Set AF 
GAIN to mid-scale.
2.  Tune to an area of the band with antenna connected but no
signals.
3.  Adjust the following, in order, until you cannot hear band
noise when switching between no antenna and your antenna (e.g.
ANT 1 vs ANT 2 with nothing connected to ANT 2):

a.  Preamp Off
b.  Attenuator (6/12/18 dB)
c.  RF GAIN

4.  When you can no longer hear band noise, then increase RF
GAIN until it just becomes comfortably audible (but not beyond
that point).

         Anytime I hear people complain about Orion being
"noisy", it is usually a sure indication there is too much
gain in their setup.  The above is adapted from a paper
Sinisa YT1NT wrote below, but it was prior to 1.372 when
Threshold and RF GAIN were integrated into one control.

http://www.geocities.com/va3ttn/UsingOrionRX.pdf

                                         73,  Bill  W4ZV