[linrad] noise blanking comparisons

[wb9uwa@xxxxxxxxxxx]

On 12 Jul 2003 at 14:14, Leif Asbrink wrote:

> Hi Ron,
> 
> > Greetings all. I am interested in weak signal HF CW and have been
> > drawn to investigate Linrad because of Lief's reputation and my
> > desire to try to be just behind the bleeding edge. I haven't got
> > Linrad running yet so I was especially interested in the WAVE files
> > W3SZ provided. I listened to them carefully.
> Please note that Linrad still has only weak signal CW mode, the
> SSB mode is actually still the weak cw mode but you can put an
> alternative set of parameters that fit SSB bandwidth.
> 
> As a consequence the blanker does not work well on strong signals
> unless one makes adjustments to the blanker levels which in turn will
> not make the blanker optimal for weak signals. You can hear this
> malfunctioning as a strong distortion on the loud SSB signal while the
> weaker station is not distorted.
> 73
> 
> Leif  /  SM5BSZ


Hi All,

From what I have seen, one thing that is normally incorporated in an SSB
noise blanker is AGC. This tends to decrease distortion on strong signals. A more advanced
way I have seen and done myself is to sample the linenoise from a passband
close in frequency to the SSB signal, but the passband does not include
the SSB signal. In my implementation of this technic, some distortion still
resulted on the SSB signal from intense line noise, but overall it was an
improvement. No doubt, my blanking gates and/or pulse timing was less then
perfect.

Still looking forward to getting wideband Linrad going for myself.

73, Jim Shaffer, WB9UWA.


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