[hpsdr] Panadapter scrolling in PowerSDR...

[Glenn Thomas]

Here's a datapoint that may or may not be relevant.

I've been running PowerSDR for several years over several different 
versions on my SDR-1000, followed by my Flex-3000. The behavior 
described has been present in all versions of the Flex software I've 
used, from v1.8.x through v2.3.5.

My assumption is that as I tune, the sum being made to compute the 
average level in each frequency bin doesn't have time to collect the 
requisite number of samples in each bin while I'm tuning. The method of 
tuning (wheel or 'grab & grope') doesn't seem to matter. The speed of 
tuning does.

If the computation of the average for each bin assumes a fixed number of 
samples, the resulting value with fewer samples will look lower, 
depending on how many samples were actually added to each bin. Assuming 
a fixed number of samples instead of keeping a separate count for each 
bin would be computationally more efficient - my assumption is that is 
why this effect on the display is seen.

I don't 'wheel tune' very much with the SDR. I find the 'point and 
shoot' method, coupled with an appropriate frequency step size and 
display size, to be much more effective.

If this display calculation does not depend on which hardware is being 
serviced (Flex or HPSDR), I would expect to see the same behavior with 
PSDR/HPSDR that I do with PSDR/Flex.

73 de Glenn WB6W

On 3/21/2012 3:44 PM, n3evl wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
> Re: PowerSDR v 2.2.3 (W5WC - 2/10/12) RX2 versus 2.2.3 (B) (W5WC - 
> 9/25/11)
>
> I've noticed an apparent change in the behavior of the Panadapter when 
> scrolling left or right when tuning.
>
> I typically run the Panadapter with some amount of averaging (750mS) 
> and typically use a 1KHz or 500Hz step size when using SSB.
>
> I've noticed when tuning/scrolling e.g. using the mouse wheel, that 
> the signal levels across the display area momentarily drop making it 
> hard to estimate if you've moved the mouse wheel enough clicks to 
> bring the signal of interest into the passband - so I find myself 
> overshooting or doing click-stop-click-stop to determine where the 
> signal now is relative to the passband.  If I turn averaging off, the 
> real-time response to tuning adjustments is better.
>
> I've experimented with different amounts of averaging time but cannot 
> find a suitable value.
>
> I've compared behavior with the older version of PowerSDR mentioned 
> above and the behavior is quite different.
>
> I'm wondering if something changed in how the display is refreshed to 
> accommodate the 2nd RX window (although this behavior is apparent  
> even when RX2 is not activated.
>
> I'm using WinXP SP3, single Mercury, Penelope, Metis,  Excalibur - 
> usual suspects.
>
> 73, Pete, N3EVL




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