[hpsdr] WSJT VAC, ALC and PowerSDR mRX PS

[Warren C. Pratt]

Hi Conrad,

I don't know about the noise burst.  However, I can comment on the way 
the ALC works.

First, and perhaps most important for your concern, the ALC NEVER 
applies any gain greater than 1.0.  If merely sits on the sideline 
watching the incoming signal and, if/when it sees a signal coming on the 
horizon that is too large, it gradually reduces the gain so the signal 
peaks at 1.0.  Once the peak has passed, it gradually increases the gain 
back to 1.0 (unless, of course, there's another peak coming that 
requires gain reduction).  Also, there is zero "ALC overshoot" in this 
system.  There is no option to disable the ALC; however, as I described, 
it just sits on the sideline and watches unless there is an 
over-amplitude signal on the horizon.

That said, there are a few features that DO offer greater than unity 
gain:  Compressor, Leveler, and Equalizer.  Those can all be deactivated 
and I suppose they should be for digital modes.

I doubt that this solves your problem; however, perhaps it might offer 
other ideas of what could be generating this noise burst.

73,
Warren  NR0V

On 10/11/2014 2:07 PM, Conrad Farlow wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> I am using an ANAN-10 with the latest version of PowerSDR mRx PS. I 
> have VAC working well with WSJT but I get a burst of noise just before 
> WSJT starts generating audio. It is 20dB below the modulated audio and 
> I suspect that is due to some kind of expander action on the ALC. I am 
> driving a transverter and have only 500mW output to do so. My TX is 
> very clean but is there any way of getting rid of this, in fact 
> turning the TX ALC off altogether? I don't need it as the audio level 
> is tightly controlled and I have a the TX gain set at around 75dB. 
> There is no way that I am going to overdrive anything.


 1413073177.0