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LF: Re: Spectran Beta 2c

To: "LF-Reflector" <[email protected]>, "amrad" <[email protected]>
Subject: LF: Re: Spectran Beta 2c
From: "'Geri' Kinzel, DK8KW" <[email protected]>
Date: Mon, 24 Apr 2000 07:28:22 -0400
Reply-to: [email protected]
Sender: <[email protected]>
Von:    Alberto di Bene, INTERNET:[email protected]
An:     "'Geri' Kinzel, DK8KW", DK8KW
Datum: 24.04.100 12:55
BE:     Re: Spectran Beta 2c

Hello Geri,

             yes, there is an answer to your question about the 'fuzzyness' of 
It all boils down to how Spectran works, and the 'hidden averaging' it does on 
received signals. I enclose here following an explanation I gave to Rex Moncur 
this subject. He was asking me if/how Spectran does perform an averaging on 
what it
receives. What happens in your case is that when your CPU is more loaded, the
overlapping  factor (defined below) decreases, and with it the 'fuzzyness'.
Feel free to post this message to the newsgroup you mention.

Alberto   I2PHD

----------------------- attached message 
            I have been away for a few days, please excuse the delay in 
In its present implementation, what Spectran does is the following :

When you activate the 'Average' push button, a running average is computed on 
last five samples, BUT it is applied only to the upper part of the display, 
i.e. the
spectrum-analyser-like waveform. The waterfall is, presently, unaffected by the
computed average. This for reasons too long to be explained here. This has 
changed in the next beta (almost ready), where also the waterfall is subject to
averaging, which is user-selectable, from 1 (no averaging) to 100.

But the story doesn't end here. When computing spectra with high resolutions, 
you are
faced with a dilemma : if you update the waterfall only when a completely new 
set of
values are computed, then you might end up with a very slow refresh rate, one 
let's say, 30 seconds or one minute, which not always is what is desired.
To overcome this, the technique of overlapping is used, where you apply a 
sliding window
to the data, reusing a portion of the old data together with some new ones. 
This permits
a much frequent updating of the screen. However, a side effect of this 
technique is a sort

of averaging applied to your displayed data. Spectran applies a variable 
factor, continously measuring the CPU load, to keep the CPU near to full 
Hence, also the averaging effect is varying, depending on the instantaneous CPU 
In the upcoming beta, this has changed, in the sense that you can choose 
whether continue
to use this method, or set a fixed overlapping factor (which of course must be 
with the cycles your CPU can deliver to the program). Setting this factor to 1 
eliminate altogether whatever averaging is done on the display (and will make 
refresh rate slower).

Hope this answers  your question,

Alberto   I2PHD

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