Hi Grant, etc,
What you say about the "distortion" actually being the noise that had been
suppressed until the cw element or ssb signal raised the gain is accurate.
There
is added distortion, though, so it has a different sound.
At the risk of boring some readers, I'll attempt to figure this out.
Let's see, a normal gain stage has constant gain,
out = a * in, where a is the gain (and a fixed value)
But the NR, which I believe is a downward expander, is a non-constant gain (or
attenuation, if a < 1), and more importantly, is a function of the input level,
so
out = a(in) * in
If we figure that the gain is proportional to the input,
a(in)= b * in, where b is a constant (and might be what the user can adjust)
then the equation probably looks like this,
out = b*in * in
or
out = b*in^2
Now since the input signal, in, is made up of various signals, noise being one
of them, and since this is a nonlinear function (a modulator/mixer) then one
can
see that all kinds of intermodulation products are produced, causing the
raspiness.
It's been a while since I studied this stuff, so if someone wants to correct or
supplement this, by all means, have at it.
73,
Lin
WB1AIW
Bonus material:
Not an expert, but want to learn and also help others to understand what cool
stuff is behind the front panel, if they are interested.
I very much enjoy my O2 and I think T-T is an admirable company. As I find
anomalies, however, I will post them to this group and to dits and bits. I
think
it's important to notify other users (and obviously T-T).
I also want to go on reading what other people discover about the O1 and O2,
and
the various firmware releases, even though they may be frustrated and come
across with strong opinions. Bring it on! Let's figure it out and find
work-arounds, if possible. Also, all questions that may seem stupid, post them
anyway. Ok, backing away from the keyboard now....:)
Grant Youngman wrote:
>>The NR does still add raspiness to the CW signal but it seems
>>to greatly reduce background noise more so than 2.032.
>
>
> Could just be AGC settings, or the characteristics of today's noise. A
> quick check at the behavior on a spectrum analyser with a constant carrier
> signal in the passband doesn't show anything significantly different from
> previous releases.
>
> I've also come to think that what sounds like a bit of raspiness is actually
> the noise in the passband varying at the same rate as the signal. With no
> signal, it sounds quiet. WITH signal, the noise comes back up. So what you
> hear is "quiet background, noisy dit, quiet background, noisy dash", etc.
> It's fairly easy to adjust a waterfall display to show this effect quite
> clearly on CW. I think (maybe) that it's the varying background noise
> creating an illusion of "distortion". Not 100% on that, but it's today's
> wild conjecture. It may also be what causes the sense of some distortion on
> SSB when NR is active, although it's hard to see anything very conclusive on
> a dynamic SSB signal.
>
> Might deserve a closer look.
>
> Disclaimer: I do not hate my Orion II. I am not bashing the Orion II. My
> Orion II is not for sale. I'm only feeling the side of something large,
> gray, and hairy in an attempt to figure out what it is, and maybe learn
> something in the process.
>
> Grant/NQ5T
>
>
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>
>
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