IQ File Playback: Panadapter Doesn't Move When Tuning

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WB4AIO Kevin
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IQ File Playback: Panadapter Doesn't Move When Tuning

Postby WB4AIO Kevin » Sun Sep 10, 2017 2:58 pm

On my new (to me) Anan 10 with v3.3.9, I can successfully record 384 kHz of spectrum and play it back, even tune around on the recorded spectrum while playing it back.

BUT the panadapter display does not move when I am doing that tuning around during playback, quite unlike tuning the received spectrum live. (My old Flex SDR-1000 tunes its recorded IQ spectrum just as if it were live, with the panadapter traces moving as I tune.)

Is this non-moving panadapter display during IQ playback normal and expected? Or am I doing something wrong?
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W1AEX
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Re: IQ File Playback: Panadapter Doesn't Move When Tuning

Postby W1AEX » Mon Sep 11, 2017 8:09 pm

Hi Kevin,

I have found that it does not work for me unless I enable the CTUN button (underneath the AVG and PEAK buttons in the GUI). When CTUN is enabled I can tune around in the panadapter normally while playing back an I/Q recording. I'm not sure if the way I do this is normal behavior for OpenHPSDR, but it seems to work.

73,

Rob W1AEX
"One thing I am certain of is that there is too much certainty in the world."
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WB4AIO Kevin
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Re: IQ File Playback: Panadapter Doesn't Move When Tuning

Postby WB4AIO Kevin » Wed Sep 13, 2017 2:52 pm

W1AEX wrote:Hi Kevin,

I have found that it does not work for me unless I enable the CTUN button (underneath the AVG and PEAK buttons in the GUI). When CTUN is enabled I can tune around in the panadapter normally while playing back an I/Q recording. I'm not sure if the way I do this is normal behavior for OpenHPSDR, but it seems to work.

73,

Rob W1AEX



Thanks, Rob!

When I do as you suggest, I can now see my passband moving around a stationary spectrum. But I still don't see what I thought I would see, my spectrum moving against a stationary passband -- as in normal tuning.

Is what I am seeing normal?

Thanks again,

Kevin.
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Re: IQ File Playback: Panadapter Doesn't Move When Tuning

Postby W1AEX » Thu Sep 14, 2017 3:54 pm

Hi Kevin,

I have not played around with this feature at all so I am hesitant to say that it is working as it's intended to. I believe that I am seeing exactly the same behavior you are describing and it does seem to be broken:

Tuning does not track in the panadapter with CTUN disabled. When CTUN is enabled, the tuning works as expected until you approach the edge of the panadapter display at which point the tuning no longer synchs up and the audio does not match the selected signal in the panadapter, although I believe the displayed VFO frequency does track with what you are tuned to. When I tune back to the original frequency span the signals do track correctly again. I made a brief video of the behavior I am seeing. Is it what you also observe?



I can take a look at some older versions of OpenHPSDR (as far back as 3.2.10 circa 2014) and see if the ability to tune in the panadapter window without CTUN enabled was present. It does look as if things aren't working correctly at this time.

73,

Rob
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Re: IQ File Playback: Panadapter Doesn't Move When Tuning

Postby W1AEX » Thu Sep 14, 2017 7:20 pm

A quick follow-up after playing around with OpenHPSDR v3.2.10 this afternoon. The IQ tuning behavior with v3.2.10 is the same as v3.4.2 when CTUN is not enabled. The VFO frequency appears to be accurate but the displayed band of stations in the panadapter does not move at all. With CTUN enabled, when the panadapter is set with the zoom control all the way to the left, you can tune all the way across the panadapter, from top to bottom and bottom to top. With OpenHPSDR v3.4.2, with the panadapter zoom control set all the way to the left, you can also tune from top to bottom and bottom to top as long as you don't invoke the re-centering trigger. It seems to lose synch as it automatically bounces you to the center. You can get it to synch up correctly again by moving all the way across the panadpater and again invoking the re-centering trigger on the other side of the panadapter.

So... going back to your initial question, with OpenHPSDR (going as far back as v3.2.10) it looks like when you are tuning through a recorded IQ file with CTUN disabled you will not see the stations in the panadapter moving through the center filter passband (normal tuning) as you change frequency. For the stations that are displayed in the panadapter to track accurately with the VFO frequency, it looks like you have to enable CTUN where your passband moves through a stationary spectrum.
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WB4AIO Kevin
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Re: IQ File Playback: Panadapter Doesn't Move When Tuning

Postby WB4AIO Kevin » Mon Sep 18, 2017 10:30 pm

Thank you, Rob, for doing all that testing for me.

I am bit disappointed in the inability to tune the recorded spectrum with a moving display -- which I can do even on my relatively primitive Flex SDR-1000 -- but I suppose with all the excellence built into these rigs I should not complain too much.

With my best,

Kevin.
Better fidelity means better communications.

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