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[Linrad] Re: mercury as a front end
- Subject: [Linrad] Re: mercury as a front end
- From: Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>
- Date: Thu, 12 Feb 2009 14:55:14 -0400
> I believe that Linrad supports Perseus and SDR-IQ?
Yes. It does.
> the data from these sounds like it would be quite similar to Mercury
Yes. The data format is not the problem.
What is different (very different) is the way Linrad has to tell
the SDR-IQ and the Perseus what frequency to select, attenuator
and filter settings etc and how to get the data from the
respective dll/linux driver.
Presumably Mercury is completely different from both of them.....
> there is the issue of how to have two (H+V) inputs.
> That would require two IQ channels in OZY
> But you could have two OZY boards and use two USB ports, no?
> Doing that would require no modifications on the HPSDR side.
This is not correct. To make it meaningful to have two
channels for H and V, both channels have to be dreived from
the same clock. That can be fixed since both Mercury boards
can be locked to the same frequency standard (??)
There are more problems though, the FPGAs on the two boards
have to be synchronized so the down-sampling process runs
synchronized in the two Mercury boards. This could be easy
if pins are available to allow one FPGA to send sync signals
to the other.
Another problem is sample timing. Somehow both USB streams
have to be synchronized. Presumably that could be fixed with
some additional wires between the two systems.
In all it does not seem practical. It should be possible
to allow two Mercury boards to share the same data line to
the OZY board. The Mercury would have to have a threestate
line driver so they can be turned one on and the other off
while they alternate to send data. The maximum bandwidth
of the system would have to be a factor of two lower,
but as I understand it would still be large enough.
Allowing two Mercury boards is hopefully just a software
problem (FPGA programming.) Should the output pin need
a tri-state buffer, that would be an easy mod.
Leif / SM5BSZ
> I am very interested in this
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