[Discuss-gnuradio] QT GUI Waterfall Sink: frequency mismatch

[Ellie White]

Hello,

 

I have constructed a small loop antenna with the intent to monitor the signal strengths of VLF submarine communication stations in order to detect sudden ionospheric disturbances (caused by solar activity). I have this antenna connected to an upconverter and RTL-SDR dongle, and have been testing it with a function generator using two different softwares: SDR# and GNU Radio. The problem I am having is that when I transmit a 24 kHz test tone, it shows up as ~24 kHz above the LO frequency on my SDR# spectrogram plot, but when I transmit the same 24 kHz test tone, on the GNU Radio waterfall plot it appears to be only 5 kHz above the LO frequency – I am wondering why that might be? (I attached my grc flowgraph if that would be of any use). I am very new to this, so any advice would be much appreciated! If any more info is needed please let me know.

 

Thanks in advance!

 

Ellie

 

rtl-sdr.grc
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