[Elecraft] Regarding the K3 and high QRN levels

[Don Wilhelm]

Nate,

The K3 has many ways of combating both QRM and QRN.  Admittedly, dealing 
with QRM is the easiest of the two - just narrow the bandwidth and 
position the passband for the best response.  While narrowing the 
bandwidth will reduce the noise also, that alone is often not enough.

The K3 combats QRN with the noise blanker and noise reduction.  The K3 
noise blanker can be either IF (analog) based or DSP based (or both).  A 
Noise Blanker does exactly as the term says, it creates a "hole" in the 
signal path for the time of the noise - if the holes are too big, 
distortion of the received signal will take place - how aggressive those 
'holes' are depends on the settings used, and those settings are under 
control of the operator.  A noise blanker works best on short impulse 
type noise, like that from automotive ignition, it will not do as much 
for slow risetime and more distributed noise such as powerline noise.  
In any case, the setting should be adjusted to minimize the noise with 
as little distortion of the received signal as possible - the K3 has 
controls for that.

Noise reduction is a different animal - it operates on correlation 
principles.  It looks for something that appears to be a signal in the 
midst of noise, and builds a filter around that "signal".  The K3 has 32 
different settings for noise reduction, some more aggressive than 
others, and there is no one NR filter that is best for both CW and SSB - 
the variety of settings allows the user to set one for CW and another 
for SSB.  Since the NR in the K3 creates a filter, it can make the 
signals sound "hollow" - perhaps that is what the reviewer called 
"reverb".  The solution is to turn NR off or use a less aggressive setting.

The user can (and should) experiment with the particular noise found at 
each location  and on each band (for each season of the year) - the 
noise encountered will be different for each combination, and no "one 
size fits all" exists.  The K3 does provide a variety of tools to combat 
noise, but they must be used with a little thought to find the best for 
any one situation.  I guess the fact that the K2 does provide this 
variety of control can be disconcerting to someone just turning the K3 
on and trusting that it will attack noise "magically".  I prefer to have 
the level of control offered by the K3, but mine is only one opinion - I 
can run the radio, the radio does not run my operation.

It sounds to me like the reviewer you ran across on EHam simply turned 
on the K3 NR (or NB) and expected magic to happen - it will, but it may 
not necessarily be good 'magic' in all cases, it depends on the noise.

The K3 DSP is an integral part of the radio, not an "add-on", so it 
cannot be turned off.  The DSP NR can certainly be turned off, or set to 
something less aggressive.


73,
Don W3FPR

Nate Bargmann wrote:
> I'm lurking this list to gain a feel for the K3.  As it seems to be the
> hot item these days, it's growing (glowing?) reputation makes it worth
> looking into.
>
> Recently, a thread took place on eHam (I know, I know...) about an op's
> issue with another DSP based rig and high levels of QRN.  A comment in
> the thread from another op leaves the impression that his K3 also has
> the same response to high levels of QRN, a sort of reverb as he
> described it.  Here is the thread in question:
>
> http://www.eham.net/articles/23975
>
>
> My questions are twofold.  First, is the "reverb" common or is it just
> certain ops who notice it?  Second, from my research I know that the K3
> is heavily DSP based, but also has provisions for IF filtering.  Can te
> DSP essentially be "turned off" or otherwise disabled so that it
> functions as an analog rig which posters in that thread claimed as
> superior.  Perhaps this is much to do about nothing.
>
> Don't get me wrong, I'm quite impressed by the various videos I've
> watched of the K3 in action which is the closest I can get to operating
> one before I buy.  The numbers and the reviews look very good and I'm
> considering purchasing one later in the year.  The QRN issue with DSP
> took me a bit by surprise which is why I'm asking.
>
> Thanks!
>
> 73, de Nate >>
>
>