[Elecraft] [Elecraft-K4] Zero to 500Hz noise in DATA mode

[Dave]

Rolling off at 150 Hz is not an issue with FT8. I haven’t had my radio long enough to really give it a good look. My reply before was based on what the other person stated with the “hump”. 

I do use the USB to PC for digital and in very limited use have not had an issue except a couple of times in Fake It mode the radio did not return to correct RX frequency. Only a couple of times with R29. Haven’t had time to test R30 as I was preparing and traveling to Dayton. 

Dave wo2x

Sent from my waxed string and tin cans. 

> On May 26, 2022, at 3:10 PM, Steve WB3LGC <email at nr3i.org> wrote:
> 
> 
> I asked about this same thing for my KX3 and never got any interest (or reply).  I was expecting flat from 0.01 to xxxx.0 for the K4D.  Better, but not zero point zero.
> 
> With input from many, maybe it will happen (for KX3, too).  Maybe CESSB for the KX3 ??  
> 
> The roll-off is also an issue for Winlink with VARA, too.
> 
> 
> 
> 73, steve WB3LGC
> 
> 
> 
>> On 5/26/22 13:04, Rob Sherwood wrote:
>> Speaking for roll-off, there is a significant audio roll off in the analog output on the high end on the order of 8 dB, dependent on the selected DSP bandwidth.  I would like to see this fixed, too. 
>>  
>> 
>>  
>> I don’t understand why there is any low-frequency roll-off in Data mode. 
>>  
>> Rob, NC0B
>>  
>> From: Elecraft-K4 at groups.io [mailto:Elecraft-K4 at groups.io] On Behalf Of Maurizio I2NOY
>> Sent: Thursday, May 26, 2022 9:49 AM
>> To: Elecraft-K4 at groups.io
>> Subject: Re: [Elecraft-K4] Zero to 500Hz noise in DATA mode
>>  
>> Dear Grant,
>> 
>> in data mode K4 applies filtering below about 150 Hz with some ringing on the cut-off frequency.
>> 
>> I already submitted here some pictures of WSJTx waterfall of K4 and Anand 7000 DLE MkII. It seems that there is not any interest from anyone to flatten the audio curve in data mode on lower frequencies or move the cut-off lower than 100 Hz.
>> 
>> If you search my posts on this group, you can see them.
>> 
>>  
>> 
>> Best 73s,
>> 
>>  
>> 
>> Maurizio I2NOY
>> 
>>  
>> 
>> Il 26/05/2022 15:32, Grant Saviers - KZ1W ha scritto:
>> I've finally got my K4 fully integrated in place of my Maestro/6700. The struggle to get enough CAT controls was finally resolved.  The flexibility of Flex's CAT architecture was really missed. 
>> 
>> One significant RF difference immediately noted is the noise (phase noise?) in the DATA spectrum display with the LO bandwidth set to zero.  The 6700 had none, at least down to a few tens of Hz.  The K4 noise appears bad enough that WSJT will have difficulty decoding the DX and FOX stations that tend to play as low as 200Hz.  Weak stations are already hard to see on the display.  OTOH, the top end of the DATA chosen bandwidth (3500) seems cleaner than the 6700. 
>> 
>> Being a total newbie to the K4 is there a means to reduce the low frequency noise?  Or is this a needed K4 DSP software fix? 
>> 
>> Grant KZ1W 
>> 
>> 
>> 
>> 
>> 
>> 
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