Linrad Spur Removal

[VK2KU <clearmail.com.au; vk2ku@xxxxxxxxxxxxxxxx>]

I have not seen discussion here of Linrad Spur Removal in recent
times.
At present the moon is down in VK most of the daytime, and the grass
in the paddock is too wet to mow although the need is desperate, so I
thought I would test the Linrad Spur Removal function :-)
I will add some comments on this to my Linrad-SDRIQ setup pages, but
before doing this I thought I would air my thoughts in this forum.

There seems to be no good reason not to use the Autospur option, which
has the advantage that manual removal of a particular spur may not
work for one of several reasons, whereas Autospur will pick it up
sooner or later!
Somehow I expected to see all my computer birdies vanish instantly,
whereas the actual process took several minutes to eliminate (or
reduce) between 10 and 20 birdies. Even then some of them reappear,
perhaps as they or the SDR-IQ calibration drifts, and are then picked
up again and eliminated.
The little box at the top RH corner of the main waterfall changes from
yellow (on) to blue (off) when you click it, and the number of treated
spurs is displayed immediately above that.

The overall effect is very impressive in reducing lots of spurs to a
manageable level (depending on how dirty they are) and eliminating
others. It is likely that my settings were not optimal, so to enable
Leif or anyone else to comment, this is how I had things set up:
Enable AFC/Spur...  2 (Autospur)
AFC lock range 150 Hz
AFC Max Drift  100 Hz/min
Enable Morse Decoding  0
Max number of spurs to cancel  100
Spur time constant (0.1s)  1 (notch BW = 10Hz)

I understand this to be an aggressive setting.
My FFT2 bandwidth is 5Hz (for JT65B)
FFT2 size = 32768
Sampling rate 111 kHz
so each FFT2 transform (I and Q) takes about 0.6s (I think).

I recall a comment by Leif on his website that using too aggressive
settings will actually eliminate a CW signal, in spite of its
interrupted nature. What about a JT65B sync tone? Is there any danger
that the very signals I am trying to see on the main waterfall will be
eliminated as supposedly unwanted spurs?

Comments welcomed.

Guy  VK2KU
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