[Elecraft] [k3] NB & Chirp

[Duncan Carter]

Assuming a simple blanking action that switches off the signal path 
during the blanking pulse, you might be perceiving this as modulating 
the input signal at the repetition signal of the blanking pulses.  Let's 
say that you have the signal tuned to the default center of the cw 
passband at 600 Hz.  If the blanking pulse has a repetition rate of 
twice mains frequency where the mains frequency is 60 Hz, then you might 
be hearing that as a 600 Hz signal modulated by 120 Hz pulses in 
probably a complex manner which you might perceive as a chirp.  
Practical use of a blanker is always a trade-off of noise reduction vs. 
distortion.  The K3 blanker is flexible and can even be used to reduce 
and/or eliminate key clicks in some circumstances.  I was able to 
practice this during last weekend's 160 test where a local, K0RF, was 
kind enough to provide a big signal with clicks throughout the contest; 
the clicks could be reduced by up to 4 S-units on the K3 indicator with 
the right blanker settings, improving the readability of nearby weak 
signals.

73, Dunc, W5DC

Wes Stewart wrote:
> Thanks Merv,
>
> So it isn't my imagination as some have inferred.
>
> Wes
>
> --- On Tue, 12/8/09, Merv Schweigert <k9fd at flex.com> wrote:
>
>   
>> From: Merv Schweigert <k9fd at flex.com>
>> Subject: Re: [Elecraft] [k3] NB & Chirp
>> To: "Wes Stewart" <n7ws at yahoo.com>
>> Cc: "Elecraft Reflector" <elecraft at mailman.qth.net>
>> Date: Tuesday, December 8, 2009, 8:33 AM
>> Yes, I find on DSP settings on the NB
>> over about 6 that there are some
>> type of artifacts that make the signal  chirp or some
>> sort of distortion.
>> Merv KH7C
>>
>>     
>>> I worked and have since been listening to J79WE on 40m
>>>       
>> CW for some time.  The wind is blowing about 40 mph so
>> the power lines are acting up and I've been tweaking the
>> noise blanker.
>>     
>>> While playing around I noted that his signal had
>>>       
>> developed some chirp.  I thought that strange, since he
>> was clean when I worked him.  I fired up old reliable,
>> my TS870 and listened to him and he was T9 with no chirp
>> (and no audio distortion).  On the K3 he definitely had
>> chirp, then I happened to turn off the noise blanker and the
>> chirp went away.
>>     
>>> The Noise blanker setting were IF=MED4 and
>>>       
>> DSP=T3-7.  The chirp seems to be related to the DSP
>> part of it.
>>     
>>> Anyone else notice this?
>>>
>>> Wes Stewart,  N7WS
>>>
>>>
>>>
>>>
>>>        
>>>
>>>       
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>
>
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