I'm running GQRX on Mac OS X 10.11.6 hooked up to an RTL-SDR dongle. I noticed when I'm tuned anywhere between ~56 MHz on down to 25.680 MHz I see evenly spaced signals on the FFT. But when I tune to 25.679, they disappear completely.
On the higher end, the signals are faint (here I am tuned to 56 MHz):
They become more pronounced as I work my way down (here I am tuned to 43 MHz):
They are most pronounced when I'm tuned to 25.680 MHz. But when I tune to 25.679 MHz they disappear entirely. Here I am switching back and forth between 25.679 and 25.680 MHz:
What's causing this? Since I see signals below 25.3 MHz when I'm tuned to 25.680 but they disappear when 25.679 I tend to think this is a bug. If so, is it hardware or software related?
The signals are more pronounced tonight. Each one has a valley surrounded by two peaks:
The one I'm tuned to in the image above has peaks at 27.03 and 27.05 MHz. The first peak is at about -60 decibels and the second one is at -50.