[Elecraft] Horrible APRS QRM on 2 Meters

[Wayne Burdick]

Thanks, Guy.

A couple of other tips: 

1. A small amount of NR (noise reduction) can be used along with the noise blanker to perform a bit of signal clean-up.

2. Most of us run with too much gain and/or too much AGC, in some cases making it sound like the noise blanker is doing less that it really is. I strongly recommend starting with preamp OFF and experimenting with AGC off as well to really hear the effect of the NB.

3. If you’re using CW, crank down the WIDTH control and also try APF. This can remove even more noise with zero signal degradation. (The APF works wonders on weak signals near the noise floor.)

73,
Wayne
N6KR


> On Jul 28, 2018, at 10:17 AM, Guy Olinger K2AV <k2av.guy at gmail.com> wrote:
> 
> Although I agree with other points, the DSP noise blanking does not work by
> pulse-closing the analog 15 kHz IF. It works in the number soup which is
> after the high IF, *and* after the low IF, *and most importantly* after the
> analog to digital conversion. DSP NB, being accomplished in the number
> soup, is not restricted to the limits of analog methodology. While the
> signal being corrected is *representative* of the low IF, it is not
> accomplished *in* the IF circuitry and is subject to any outcomes of the
> analog to digital conversion.
> 
> A good rule for using the IF labeled NB in the K3, is to only use it if it
> makes NB on ***that particular noise*** work better, otherwise don't use it
> at all. Some of the noise I have around here from time to time is better
> blanked with IF + DSP. Other noise is blanked better, sometimes much
> better, by DSP only. I'm to the point now where I know what each noise
> around here sounds like and can put up the best NB settings right away.
> Also some combo's that work well on 160 work poorly on 80m and up.
> 
> For the new user of K3 NB, remember that METHODS are also being switched as
> you turn the knob, it's not at all like a simple 1 to 10 scale. You can use
> a (1st) IF method, and a DSP number soup method, or IF only or DSP only.
> When you use both methods, they operate separately in series, with the IF
> method necessarily being applied first. It appears, to me at least, that
> some DSP methods are diminished by running the IF blanking at the same
> time.
> 
> For 2 and a half years I had an AC pulse noise on 160 that IF NAR4 + DSP
> T1-7 or T2-7 cleared out to below the band noise in a certain 5-6 kHz range
> and less efficiently away from that. Contest operation in that range was
> equal to no pulse noise. It turned out to be leakage in a splice in the
> 13kV buried line to easterly neighbors' power transformer. When the splice
> hard arced this spring, that noise went away and has never returned. The
> fuse blow up on the feed pole across US 64 sounded like a bomb. It rattled
> windows. They replaced all the buried 13kV line off that aerial 13 kV feed
> to our transformers. Noise has never come back. Currently the IF blanker is
> not useful for any noise I run into here. That could change, of course, at
> any time  :>))
> 
> 73, Guy K2AV
> 
> On Sat, Jul 28, 2018 at 12:10 AM, Jim Brown <jim at audiosystemsgroup.com>
> wrote:
> 
>> . Fact is, that they are BOTH working in an IF, one in the first IF and
>> the other in the second. FAR better to call them IF1 and IF2. NOW it
>> becomes clear which is post-xtal filter.
>> 
>> 
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