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

[Wes]

Thanks for the mention of the Collins document.  I had not seen it and after a 
search and finding it, I was amazed at how much of it was similar to what I 
established independently.

If you happen to look at the bottom of my QRZ bio you can see the mobile rig 
belonging to a boyhood neighbor.  He gave me my first exams, but I wouldn't call 
him an Elmer in the mentoring sense.  He built the mobile because a powerline 
running through his property prevented him from hearing anything.  That was 
until Collins came out with their noise blanker for his 75A-4. (I never 
understood why he didn't just move but I think his trust fund income came after 
he moved there.)

Wes  N7WS


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