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

[Wes]

  I have one little nit to pick with this.  In a properly designed blanker, 
there is no requirement that the noise be repetitive; blanking should occur on a 
single pulse or on random pulses.  Blanking becomes ineffective when 1) an 
undesired signal appears in the detection bandwidth that exceeds the threshold 
and triggers the blanker more or less continuously or 2) the duration of the 
noise pulse is so long that intelligibility suffers. Atmospherics fall into this 
latter category.

See: http://k6mhe.com/n7ws/Noise_Blanker.pdf  for more of my opinion on this.  
(The missing text in the last paragraph was not my fault.)

Actually now that I think about it, I have another nit.  Although the control on 
the K3 front panel says "RF Gain", which I guess differentiates it from AF Gain, 
it really should say "IF Gain".  It has absolutely nothing to do with affecting 
the gain ahead of the i-f amplifier.  Front end attenuation can affect noise 
power into preamp and/or the first mixer (and noise blanker circuit); "RF Gain" 
cannot.  In fact RF Gain is applied first to exactly the same point as AGC, the 
post-filter FET.  The FET can't tell the difference, which might be news to the 
guys who turn off the AGC and "ride the RF gain control."

Wes  N7WS

On 6/13/2019 6:09 AM, Bob McGraw K4TAX wrote:
> The Noise Blanker only affects repetitive pulse noise such as ignition type 
> noise.  Lightning and atmospheric is random noise. As to the Noise Reduction, 
> I find that use of the Attenuation and RF Gain control is far superior to 
> using DSP systems.  Also remember it is Noise Reduction and not noise 
> elimination as many seem would like to believe.  If one realized 6 dB of noise 
> reduction using the system that's good.   At the same time, any noise 
> reduction system will add distortion to a SSB or CW signal.
>
> From very authoritative source, the optimum receiver performance configuration 
> is to have the no signal band noise about 10 dB above the noise floor of the 
> receiver.    Since we can't change the noise floor of the receiver, the option 
> is to change the incoming level of the noise as presented to the receiver 
> input. The K3S receiver noise floor is about -135 dBM.   If one has a no 
> signal band noise of S-5 or -97 dBm, the difference is 38 dB. This says we 
> need 28 dB of Attenuation and RF Gain reduction.    That would be 15 dB of 
> Attenuation and about 2 S units of RF Gain reduction or 10 dB of Attenuation 
> and about 3 S units of RF Gain reduction.     This in no way changes the 
> sensitivity of  the receiver nor does it impede the ability to hear weak 
> signals. Unfortunately many hams belie that more gain is needed to hear weak 
> signals.   With receivers of 50+ years ago often the receiver noise exceeded 
> the band noise.  That however is not true with today's modern receivers.
>
> As to using the Noise Reduction,  I do not use it at all for SSB and for CW.   
> If  I do use it I find  F1 and a value of 1 to 3 about all I'm willing to 
> accept.  Of course the type and magnitude of the noise does require different 
> settings.
>
> If I use the Noise Blanker I find it necessary to first set the IF NB to OFF.  
> Then adjust the DSP through its values to get what seems to be the best 
> result.  Remember the value.  Then set the DSP NB to OFF.   Then to the IF 
> noise adjustment and find what seems to be the best result.   Leave it at that 
> and then back to the DSP Noise blanker and set it to the previous obtained 
> value.    This optimized them individually.   I've not been successful in 
> trying to adjust both at the same time.    And remember it only works on 
> repetitive noise such as ignition noise or line noise and not random 
> atmospheric noise.
>
> The receiver gain method works best.   Hope this helps.
>
> 73
>
> Bob, K4TAX
>
>
>
> On 6/13/2019 6:43 AM, Nr4c wrote:
>> This is not an easy thing.
>>
>> First, are you hearing general band noise, a constant “ shhhhhhhhhhhh” or 
>> pulses as in lightning, power line, or ignition type noise.
>>
>> For band noise, the NR will be your best solution. Experiment, but don’t go 
>> too deep. Deep settings will distort and make it sound like you’re underwater.
>>
>> For the pulse noises, try IF first, again don’t use extreme settings. If this 
>> doesn’t work, try the DSP settings and see if this will work.
>>
>> I have NB set to Med4. NR is set to F1-3.
>>
>> YMMV.
>>
>> Have fun!
>>
>> Sent from my iPhone
>> ...nr4c. bill
>>
>>
>
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