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"Sharing" Waterfall engines

With the new RX8WF2 mode, is it possible to "multiplex" the two waterfall engines among several users? In other words, for users >2, pass the WF params of the user to an available engine, do the sampling/FFT and return the result and so on to the next user?

This would, of course, complicate averaging (temporal, bin - assuming either to be used), maybe even miss transient events - not to mention slow things down (even more) but if so, it could permit some semblance of a WF for each user.

Would the architecture even allow this?



  • No. Read the design document re the "acquisition time" problem:

    Most people don't seem to realize that what the Kiwi implements is pretty close to what a spectrum analyzer does. The large buffers of each "waterfall" DDC channel can fill in a few microseconds or hundreds of milliseconds depending on what zoom level each connected user has chosen. That can change in an instant. So any sort of multiplexing becomes very difficult, if not impossible, to schedule. Things might be different if the FFT was done on the FPGA, but it isn't currently. It probably would have taken me an extra year to figure that out (fixed-point FFTs are tricky) and the FFT may not even have fit into the FPGA.

    That's why Twente WebSDR is such a beautiful thing. A US $1000 GPU card just blasting away doing a 2 million point FFT in realtime supporting >400 simultaneous users. But you wouldn't be very happy if the Kiwi cost that much..
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