What is a Multi-channel SDR decoder receiver?
As I’ve described in my earlier posts, the DRU-244A SDR digitizer hardware contains up 16 radio channels as hardware Digital Down Converters (DDCs). These can be distributed in 4 channel blocks between different antenna inputs. One signal processor contains 4 channels and supports one input, which presents a limitation when pairing antenna inputs and receiver channels.
Integrating the multi-channel SDR receiver with external decoder software
There are several ways to integrate the DRU-244A based Quadrus SDR platform with external software packages.
- direct programming of the DRU-244A SDR hardware employing its API
- programming the SRM-3000 SDR software using its API
- and simple audio connection with virtual audio cables
All the API descriptions can be found in the documentations of the muti-channel SDR hardware and SDR software. They can be downloaded from the support page on the Quadrus SDR site: http://spectrafold.com/quadrus/support/
The first two methods requires some programming, however, the third one does not. It is very similar to connecting your old hardware receiver to a decoder software. But in this case, the receiver itself is a software too. So, we just need a virtual audio cable.
Setting up the audio outputs
In the options menu you can assign an audio out device for all of the SDR receiver channels. Also, you can select the monitor sound device as well.
If you start each channel, the sound output of the demodulator will be routed to the selected audio device. It will be a mono channel in case of CW/AM/FM/USB/LSB demodulation, and stereo in case of IQ demodulation.
The monitor channel is usually employed to monitor the given channel, and has the audio routed to the loud speakers or head phones connected to your machine. If you touch one of the controls of a given channel or press the Monitor button, the channel will be automatically monitored, and you will hear its demodulator output.
Testing multi-channel SDR decoders
After setting up the system with different virtual audio cables, I’ve tested it with some well-known digital decoders, like MultiPSK, MMVari, Digipan. All of the multi-channel SDR decoders worked fine without any problem. Even several copies can be run on different channels and operating modes depending on the available computer resources.
It is possible to connect the audio output of each channel of the multi-channel SDR decoder to an external software with virtual audio cables. It was proven to work with several digital post-pocessors, like MultiPSK, MMVari, and Digipan.