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HDSDR: Feature or Bug?

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Dec 13, 2016
Hi Folks

Preamble: This is maybe just an odd thing that could be ignored. But I would be interested in ideas
about what is really happening.

WITHOUT powering up your SDR (assuming it works off a power supply like, e.g. the Softrock).
WITHOUT plugging in your USB cable
ONLY connection from SDR to laptop is the soundcard device (si570 in my case).
The laptop is running off only battery and NO OTHER peripherals are connected. (Actually, the same
thing occurs with AC to the laptop also.) This particular laptop has a solid state hard drive but I've
reproduced this behavior with another laptop having a conventional hard drive. I've also taken the
laptop outside far away from the building in case there was something going on with the house electrical

You get a plot updating about every second with a corresponding sound i.e. once per second. It's just
a white noise type of sound. You can then DISCONNECT the USB cable so absolutely nothing from
your SDR is going into your laptop and this same plot keeps updating, on and on, as long as you want
to listen to, or watch, it.
A screen shot is attached.

Just some internal laptop noise that somehow HDSDR is recording? What is causing that
noise? And why would HDSDR even be aware of it?

Thanks in advance for helping to shed some light on this.


Dec 13, 2016
I should have mentioned that I'm using the latest stable version of HDSDR v2.70 (Nov 2013) and
Windows 10.


Premium Subscriber
Jun 9, 2010
Hesperia California
what usb device are you using the only one that works on that low of a freq is the sdr v3 if so you are not going to receive anything down that low without switching it into the q sampling mode under receivers. Also HSDR now has a new version out 2.75
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