I'll try. The short answer, in case you're not into an explanation is:
"It all depends on your circumstances, the character of your noise, the
strength of the signal you're trying to copy, how much distortion you're
willing to tolerate ... and sometimes the phase of the moon." No one
can give someone else a set of numbers that will work in every case.
The K3 has two Noise Blankers and a DSP Noise Reduction feature.
Noise blankers do exactly what their name implies ... when a sharp noise
pulse comes along, they simply punch a hole in the signal [mute the
receiver] for a short period. The adjustable things are generally the
length of the "hole" and some form of threshold setting that determines
when it decides it's a noise pulse.
The K3 has one hardware NB at the 1st IF [8 MHz] that works essentially
like any other NB. It also has one in the DSP firmware that operates on
the "number soup" from the ADC. It too blanks the signal for variable
times and under variable conditions ... because it's doing it with
arithmetic and not hardware components, it can be somewhat more precise.
Noise blankers are effective against repetitive short pulse noise such
as ignition noise from a vehicle [not nearly as common as 40 years ago]
and precipitation static. They are *not* very effective against power
line hash although sometimes they'll knock it down some if it has a
short repetitive component. They are not effective against T-storm
static much at all.
Obviously, punching holes in the signal distorts it and the longer the
holes, the more distortion. As you increase the aggressiveness of the
NB, you'll start trading noise for distortion, so the basic rule is, use
as little as possible. They're not magic.
Noise Reduction on the other hand all happens in the DSP. There are
various approaches to it, in the K3, the DSP algorithm builds a variable
filter on the fly to enhance the desired signal, thus appearing to lower
the noise. How well it works depends on it's ability to identify the
signal components separate from the noise. I have found it to be much
more effective on SSB than CW with very narrow bandpass. I rarely
operate SSB so mine doesn't get much use.
The "aggressiveness" of the NR is adjustable in the K3. The first half
of the available settings operate on the signal and what you hear is the
result. The second half mix in some non-NR'd signal with the output.
The general rule for NB [as little as necessary] sort of applies to NR
too, and again, no one can tell you exactly how to use it. That's a lot
of words to say, "NR isn't magic either."
73,
Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org
On 7/29/2014 9:48 AM, Arlen Fletcher wrote:
Greetings Elecrafters,
I’m new to the K3 (and HF in general), and I’m trying to sort out how
to get useful results from the Noise Blanking (NB) features.
I’m looking for strategies, tips, techniques, etc. for selecting the
settings for NB. With over 14,000 possible settings between the IF NB
and the DSP NB (according to KE7X’s K3 book), I find myself getting
overwhelmed and I give up on NB. Honestly, I can hear very little
difference as I go through the various NB settings, so how am I
suppose to choose the ‘right’ one?
I operate SSB almost exclusively, and I don’t use all-mode squelch -
but I need to experiment with this. I’d appreciate hearing your take
on squelch.
What’s your secret recipe for picking NB settings that work?
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