[Elecraft] K3 NB

[HankP]

Another approach -like K2AV. 

I suspect the reason there are so many differing opinions on the effectiveness for the K3NB 
is that the noise pulses from an arcing piece of powerline hardware can be so different . 

In fact the better powerline RFI folks now use a receiver that takes a picture of the waveform of 
the interference you are hearing and they go in search of where that particular waveform is 
being generated .The local APS guys ask if they can just connect to your antenna 
and record exactly what you are hearing . 

If you have an oscilloscope - I suggest you hang one across your speaker or headphone outputs 
put the K3 on AM and widest filter , use the line sync and set to 10 msec/div . 

Its interesting to watch the spikes versus what you are hearing . Obviously the K3 NB setting 
will be different for different kinds of spiking . I have seen cases where there will be 3 and 4 
spikes spaced about a half to maybe a msec apart repeating every 16.6 msec .And 
this can and usually is be imtermittent The blanker 
window can obviously be different than for a single pulse evey 16.6 msec. And the wider 
the blanking - the more of the desired signal gets chopped. 

The problem with NB in any receiver I have ever had is that a very effective blanker will 
be terrible in the presence of strong nearby signals . I had a couple Orions and the 
NB in those where as good as I ever had - BUT any stong sigs within 35-50 khz 
would pump the blanker . It was great when everybody thought the band was dead 
and I had it to myself for awhile. Otherwise it was useless. 

The ability to use NB after the IF roofing is interesting with respect to strong 
adjacent sigs BUT apparently the pulses get stretched enough that I have never 
seen DSP NB do much good on my noise. 

I have wondered about having an option in the K3 to use the sub receiver just as 
a noise receiver at someplace out of band where there are no strong signals 
(ala one of the old Collins receivers which used about 40 mhz noise receiver 
to drive the NB circuitry) 

73 Hank K7HP