[hpsdr] Multiple Independent Receivers & Mercury

[Frank Brickle]

2009/3/19 Steven Doyle <steve_doyle at o2.co.uk>


> As I understand it a single Mecury is quite capable supporting multiple
> independent receivers. I believe Phil said it could do 6, and only limited
> by our USB bandwith. The only reason that we currently have a single max
> 192KHz was so that we could use existing software like PowerSDR.
>

There are too many definitions of "multiple independent receivers" floating
around here.

DttSP sdr-core is essentially the DSP code running inside PowerSDR. A single
sdr-core instance is capable of running a fairly large number of independent
receivers inside itself. I haven't checked "fairly large" recently, but it's
probably around 16 or so without strain. The limitations on this method are
(1) all of the receivers have to be tuned within the same basic passband --
in the case you describe, 192kHz; and (2) all of the RX outputs get routed
to the same audio output, so that they can only be distinguished by their
pan position in the stereo output.

The number of receivers enabled in PowerSDR is a consequence of the way
PowerSDR is designed and built.

It is also possible to run *multiple sdr-core instances* (and thus multiple
truly independent receivers) on a suitable OS (Linux, Mac OS X, BSD).  Here,
each sdr-core needs its own IF input stream (although they can be fanned out
from a single source). The number of such independent processes is also not
small. I've run 6 simultaneous sdr-cores on a modest machine, although at
48kHz per RX. On a reasonably  capable machine, you could afford to be
somewhat more ambitious. Here, each of the sdr-cores also routes its output
independently. Note that each of these independent processes can have its
own block of multiple internal receivers, as described in the paragraph
above.

Neither of these scenarios has the slightest dependence on Mercury per se.

In both these scenarios, the limitation observed in PowerSDR is not on
Mercury or the DSP: it's on the specific application (PowerSDR).

java-sdr and sdr-shell do not have the same limitations.

73
Frank
AB2KT


-- 
Take her and cut her out in little stars,/And she will make the face of
heaven so fine/That all the world will be in love with night... -- Wm.
Shakespeare, ad lib
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