[Elecraft] [K3] Notch filter vs JT65?

[David Blake]

I agree with Jim, very strong signals will wash out a waterfall but have very little effect on decodes.  I have decoded extremely weak signals only a fewHz away from strong signals.  I leave filters at 2700hz and NEVER use anotch filter on any WSJT modes.  
73, Dave N4DB


On Sunday, August 27, 2017, 6:41:03 PM EDT, Jim Brown <jim at audiosystemsgroup.com> wrote:

All very good advice.

BUT - how close is he?  How much bandwidth is he occupying?  How many dB 
down at how many Hz from the center of his signal?

AND VERY important -- K1JT has repeatedly advised to NOT to any 
filtering ahead of WSJT-X, because the phase shift associated with the 
filter degrades decoding.

I have locals in the range of 5-20 miles from me and both they and I are 
running power (me, a KPA500).  Depending on what direction each of our 
antennas are pointed, the "red" can be pretty wide. But that does NOT 
mean that WSJT-X cannot decode signals in that red zone!  Further, the 
colors in the waterfall are absolute level at input to WSJT-X. ANY 
signal will have sidebands. If, for example, he's 40 over S9 (not 
unusual at two miles), even the cleanest of radios with modulation will 
be S9 within 200-300 Hz of his signal.

73, Jim K9YC

On 8/27/2017 11:07 AM, Bob McGraw K4TAX wrote:
> A couple of things to check. Be sure the Line Output from the radio is not set to high such that it is driven into distortion.
>
> Also check the computer CODEC gain isn't too high and it being driven into distortion. This is set in Windows Sound device Recording Level.
>
> Also make sure the ALC is ON and handling the signal. Perhaps some attention on the input of the receiver is in order.
>
> The receiver Noise Blanker should be OFF.


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