Re: P3: a modest proposal for QSY

Posted by N8LP on Aug 13, 2010; 2:32pm
URL: http://elecraft.85.s1.nabble.com/P3-a-modest-proposal-for-QSY-tp5410950p5420223.html

Technically, Joe, with PowerSDR/IF in Collapsed view you can fill the screen with the panadapter/waterfall up to the video card's maximum setting. I run my monitor at 1680 x 1200 and can fill the screen if I want to. Collapsed view is not available in the Flex Radio release of PowerSDR.

For your example 100kHz span, that would give a pixel resolution of about 60Hz, since the RBW is better than 1 pixel at that span. According to the P3 manual, the P3's RBW at 100kHz span would be 100000/450=~222 Hz. I assume they only display 450 pixels, so the pixel resolution would also be 222Hz.

PowerSDR/IF has a definite advantage in pixel resolution at wide spans. P3 has an advantage at very narrow spans since PowerSDR uses a fixed sample rate. If PowerSDR/IF is set for 48kHz sampling rate, the resolution at narrow spans would be 4x better than at 192kHz, of course.  

73,
Larry N8LP



<quote author="Joe Subich, W4TV-4">

 > What Joe W4TV is saying is that a P3 is "never more than 50
 > cycles" from the K3 frequency readout when correctly
 > calibrated.  With a 100 cycle bandwidth, this is somewhat
 > acceptable.

You take what I said out of context.  That statement was in
reference to the FREQUENCY DISPLAY.  The FREQUENCY DISPLAY is
never move than 50 cycles from the K3 FREQUENCY DISPLAY.  That
divergence is ONLY because the K3 FREQUENCY display ROUNDS to
the nearest 100 Hz (0.1 KHz).

 > However, on a Flex, I can click on a signal and be DEAD ON
 > the signal I have selected.

If you have sufficient span (visual resolution) selecting a
signal on the P3 will put you dead on in the K3.  However,
it is just like clicking on the spectrum or waterfall in
any digital program, the mouse has a one pixel resolution -
if you are trying to use a spectrum/waterfall span of 100 KHz
in a window that is 360 pixels wide (1/4 of an SXGA screen),
the BEST you can do is +/- 138 Hz (100 KHz/360).

If you are using PowerSDR (the real FlexRadio) in full screen
mode on a 1600 pixel wide screen, each pixel will represent
about 70 Hz (100KHz/~1400 - the spectrum/waterfall is not full
width) and you can get within +/-35 Hz.

The same factors apply to the P3 ... your maximum accuracy is
SPAN/DISPLAY RESOLUTION.  In the case of a 100 KHz span,
100KHz/480 +/- 100Hz ... that's one pixel and represents the
resolution limit of the display.  However, I don't see it as
a real issue since a 100 KHz wide view only makes sense on a
relatively quiet band and you're not going to be using a 50 Hz
wide filter under those circumstances.

73,

    ... Joe, W4TV