Technical Topics > SDR - Software Defined Radio

Neophyte to SDR- - question

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tybrad:
Hi all,
I am just now exploring the UTwente site (and others like it) and am enjoying it.  One thing that I cannot figure out is the diagonal signal swaths across wide frequency spectrums.  They appear to be freq sweeps over a period of time- it manifests itself as a diagonal line or sequence of dashes across the waterfall.  What is this phenomenon?

Token:
These signals are ionosondes, specifically "chirpsondes", there are several different types and they are typically run by universities, militaries, and governments.  They are used to map propagation conditions, or the way the ionoshpere is reflecting / bending / absorbing radio waves.  With this information you can predict / tell how well a specific frequency of operation will work into a specific region of the world.

T!

tybrad:
Oh yes, also:  What is down in the negative kHz regions shown on webSDR sites?  I see and hear signals, but –kHz is not possible, unless the nomenclature is unfamiliar to me.

Token:

--- Quote from: tybrad on April 08, 2014, 0944 UTC ---Oh yes, also:  What is down in the negative kHz regions shown on webSDR sites?  I see and hear signals, but –kHz is not possible, unless the nomenclature is unfamiliar to me.

--- End quote ---

Can you give a specific example (which specific web SDR including node name, what frequency you are trying to tune to, bandwidth setting, etc)?  And maybe a screen shot of what you mean?  I suspect an incorrect setting or a misunderstanding of what is being presented.  As you said, negative frequencies are not real.  There are a couple of ways to get what appear to be negative frequencies displayed using some SDRs (particularly sound card based ones, like the SoftRock series).

T!

tybrad:
I am on

http://lindsey.esrac.ele.tue.nl/

View "all bands" and the bottom waterfall shows down to zero kHz and below that.

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