[Elecraft] Help with IF Noise, DSP Noise, NR settings

[Fred Jensen]

I have never found a noise blanker to be of particular value, if any at 
all, on general power line hash [the "grass" along the baseline of a 
panadapter.  At our prior home in Auburn CA, I had a 3-phase ~70 KV 
transmission line on  running across the lower end of the property that 
connected a series of hydroelectric plants above and below us, and two 
3-phase 112 KV transmission lines on towers about 1/4 mile away.  The 70 
KV line was essentially quiet.  The 112 KV lines was perhaps S3-4 on 80 
and had a fairly high frequency sound ... I guess from the 3-separate 
phases with peaks occuring at 360 Hz.  The K3 NB was ineffective against 
it.  With the level set high enough to affect the noise level in the 
headphones, SSB was highly distorted and CW was chopped up.

Here in NV, we are about 1/2 mile from a 500 KV 3-phase transmission 
line connecting a power plant in Patrick NV to someplace up in OR, 
probably along the Columbia.  It is fairly quiet, S2-3 on 80, and again 
seems to be high frequency enough that the K3 NB is ineffective.  I've 
concluded that, while technically it all is impulsive [arcs on voltage 
peaks], the peaks must overlap enough and/or are of a high enough 
frequency that the NB either can't find them or punches too many too big 
holes in the signal.  It might be more effective on noise from a single 
phase line, don't know.

I rarely hear ignition noise from spark plugs anymore, however the 
landscape maintenance crew showed up earlier this spring to aerate and 
de-thatch the grass.  Their aerator gizmo had an old 7 HP engine with 
strong ignition noise.  The NB took all of it out just fine at very low 
settings.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 6/14/2019 11:33 AM, Bob McGraw K4TAX wrote:
> David et al;
>
> My statement is almost word for word from the Elecraft K3 manual.   
> And some from work done by Art Collins and company at Collins Radio.  
> They prescribed the function of a Noise Blanker as follows:
>
> "The following operational requirements were kept in mind:
>
> 1. Reduction of ignition noise from vehicles.
> 2. Reduction of power line corona noise occurring at 120 CPS repetition
>    rates.
> 3. Reduction of local thunderstorm disturbances.
> 4. And, in general, reduction of any man-made noise which is impulsive
>    in nature.
>
> Basically, all the above forms of noise interference are impulsive 
> functions with repetition rates than can extend up to 100 KC in the 
> case of the strokes in a thunderstorm."
>
> Those are my sources.
>
> Again both descriptions use repetitive pulse rates which are impulsive 
> in nature.    In order for a NB to function efficiently it is best 
> suited in a wide band signal path that is not restricted by filters.   
> Hence a wide IF stage of the receiver before any filtering.
>
> As to thunderstorms, since lightning contains many pulses in a single 
> stroke, the NB is suited to minimize those pulses while at the same 
> time, the bulk of the strike energy is affecting the receiver in other 
> means. Namely AGC.  Many receivers suffer grossly from this 
> phenomenon.   Fortunately Elecraft and Tentec took actions with their 
> designs to minimize this phenomenon based on the work of Rob 
> Sherwood.    And regarding thunderstorms, there is a clear difference 
> in the stroke and content of such for  a "local thunderstorm" as 
> compared to the noise from distant thunderstorms several hundred miles 
> away.   The distant thunderstorm is affected by propagation and may 
> have several wave fronts with different arrival times where as a local 
> thunderstorm only has a single wave front.   Hence the waveform is 
> quite different and the means to suppress such will be different.
>
>
> 73
>
> Bob, K4TAX