Adds Frequency Offset option to adjust the vertical freq to captured frequency center

[jwcrawley]

This is a feature to implement a frequency offset, found just below the sample rate. If at 0, Inspectrum will function as it has before, with the center at 0 Hz, with 1/2 sample rate being the positive and negative bounds (eg: -10MHz to 10MHz centered around 0 Hz)

This feature shifts the 0 to the frequency that a user captured. For example, if a user was capturing a 30MHz window centering around 915MHz, they would see:

930MHz (upper bound)
915MHz (center)
900MHz (lower bound)

We also adjust this in accordance to the frequency and the sample rate in accordance how Inspectrum normally runs. We cannot detect this automatically, since IQ captures do not record it.

[miek]

Sorry for the delay getting back to you. Thank you for this.
It all looks good to me, except for one nitpick: I think it'd be better to call it "Centre frequency". That matches what GNURadio and other tools call it, and should make it's purpose more obvious to users. What do you think?

[jwcrawley]

Sorry, work got intense else I would have responded sooner. That change is perfectly fine! Sincerely, Josh Conway

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On Thu, Oct 1, 2020 at 9:54 AM Mike Walters ***@***.***> wrote: Sorry for the delay getting back to you. Thank you for this. It all looks good to me, except for one nitpick: I think it'd be better to call it "Centre frequency". That matches what GNURadio and other tools call it, and should make it's purpose more obvious to users. What do you think? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#169 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AB5S3KIUAXBG625QS4FEFJ3SISCY5ANCNFSM4QUU7K6A> .

[catkira]

@jwcrawley I think the feature is nice. Can You rebase Your PR to the latest master branch (now main ^^) so that it can be easily merged?