[Elecraft] K4 Question

[M Cresap]

Once any FT8 passband is digitized, filtered, and decimated in a K4, there should be no need to ever apply AGC - just pass the bits over to WSJT. The decimated bit stream may exceed 16 bits, so the WSJT input processor would have to be modified to accept the additional dynamic range.


 On Tuesday, June 23, 2020, 9:12:47 PM EDT, Adrian <vk4tux at gmail.com> wrote: 

On 24/6/20 11:02 am, Jim Brown wrote:
> On 6/23/2020 4:53 PM, Adrian wrote:
>> An excessive strength FT8 signal is easy to remove with notch.
>
> Yes, BUT -- the notch introduces phase shift, which can degrade 
> decoding.  K1JT recommends running the IF wide and letting WSJT-X 
> separate signals.
Ok on that, My experience is that it allowed decode of my target RX., I 
did use narrow notch.
>
> I DO strongly differ with the advice in the WSJT-X manual for setting 
> levels. Instead, I recommend setting audio gains so that the green bar 
> indicating audio level as close as possible to the top without it 
> turning red on when strong signals are present. I find Slow AGC works 
> well for me, because both the strongest signals AND my local noise 
> vary widely.

Yes I do that all possible gain and AGC turned off on low band use, with 
green as high as 80dB with no red seen , for good weak signal decode.

Using low width roofing/dsp filtering around the signal boosts it to 
great extent, using width/shift to focus.