DSD & reversed I/Q problem

Not open for further replies.


Oct 2, 2014
Hi guy's, nice site/forum.

I've been messing about this past month or so with my RTL setup and finally after installing and testing many software applications have found a setup that works best for me for decoding - I've found HDSDR in Windows 7 to use the least resources.

Initially, I was battling with Kali-Linux for weeks and did manage to get up and running with the usual suspect projects like Airprobe for GSM using GQRX and libosmocore to have a general poke around and get a feel for things - in Linux I found from time to time that any encoded signals just simply failed to decode in DSD giving a quite boring "Slot Idle" (giving DSD the -xr switch without reversing I/Q gave same result & visa-versa).

Reversing the I/Q in GQRX resulted in DSD getting a reversed stream and it seemed happy with it, decoding the voice (all be it in reverse) and printing out the usual decode debug information.
At this point frustrated with Linux in general (being a bossy cow/lack of support for everyday hardware/poor performance) I decided to give Windows a go (as 90% of the guy's on the net seemed to be on anyway).

As above, after many trial/error software installs and finding what's what with the many Windows softwares available for use with SDR I was up and running for weeks with no problems with SDR# and Virtual Audio Cable, and than all of a sudden - decoding GFSK just halted, I was getting the same "Slot Idle" message and again giving DSD the -xr switch without reversing I/Q gave same result & visa-versa.

I have 3 RTL dongles, all the same chip and all have this problem. What was an intermittent problem in Kali Linux has now come to be a fault in Windows not allowing me to decode anything.

I've tried removing Virtual Audio Cable in favour of another virtual audio application, removing drivers etc. etc...at this point I'm lost as to what the problem may be and really suspect it's something I'm doing as this was happening across two different OS's...but then again reverting everything to default results in the same problem - I guess the only variable's common to both OS's are the hardware (soundcard or RTL chips (three of them) and me).

Not open for further replies.