Setting up MAP65 Quadrus SDR connection with virtual audio cables
In order to implement the MAP65 – Quadrus SDR connection, the output audio stream of the channel should be routed to the installed virtual audio devices in Windows. In case you have virtual audio cables installed, it is possible to select one for each channel as you can see it in the picture below.
The standard, speaker output device is used to monitor the channels in this example. The four channels of the receiver are connected to four different virtual audio cables.
We have to select one other virtual audio cable – like VAC line 5 in our example – in the MAP65 software. Finally, the streaming software can be started to connect the receiver and the decoder software.
MAP65 Quadrus SDR connection testing
We can find a strong signal in the receiver window, and the same signal will appear through the virtual cable in the MAP65 wideband spectrum display too.
Please note that the output sample rate of the SRM SDR receiver is only 48 kHz, but the input sample rate of the MAP65 is 96KHz. The VAC software makes the interpolation between the two different sample rates. Thus, the inner +/- 24 kHz part of the MAP65 display will contain valid spectrum components. The interpolation is done without any filtering, so we will see the image spectrum beyond the 24 kHz limit. If we set up a 15 kHz filter in the SRM SDR receiver, we can see the noise level in the spectrum accordingly and mirrored to 24 kHz as well.
In the picture above, you can see the signals from the generators which was set +/- 4 kHz around the nominal frequency. As you can see, the signal was positioned beyond and below the center using the IQ streams from the receiver. The same kind of signal tuning can be seen in the screen recording below.
Successful MAP65 – Quadrus SDR connection via virtual audio cables was proven using the IQ demodulator of the SRM SDR software. Virtual audio cables were used during the test, and the streaming software of the VAC package was employed for connection and to implement re-sampling between the different audio sampling rates of the two software.