[hpsdr] Looking for guidance

[Jeremy McDermond]

On Nov 10, 2010, at 5:19 PM, Erik Anderson wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> Sounds about what I heard before, that the gigabyte ethernet would permit a broader signal to be transmitted.

Only because of the increased bandwidth between the computer and the hardware.  You, in theory, can transmit as wide a signal as you can cram samples down the wire.  The USB2 connection isn't necessarily maxed out with our current system.

> I want to be able to experiment with this radio, and that includes the possibility of trying to transmit 8MHz-wide "audio data".

Technically speaking, you can produce pretty much any signal width that the DAC is capable of producing.  Penelope uses an AD9744, which is a 210 MSPS 14-bit device.  To fill every sample, it'd require on the order of 2.9 gigabit/sec worth of data.  With the current system where we're using 16-bit samples across the wire, and using the 8MHz of bandwidth (16Msps), you're looking at 256Mbit/sec on transmit.  That should be fairly easily doable on Metis.  Even on Magister, which uses a Cypres FX2 capable of 448Mbit/sec, you should be good.  As Phil said, it's a simple matter of programming.  You'd need to develop a custom image for the Cyclone FPGA on Penelope to provide appropriate filtering and such, and an image on Magister/Metis to take data from the computer in an appropriate format.  And, of course, software on the computer to generate the samples for the hardware.

> 
> On Wed, Nov 10, 2010 at 5:07 PM, Phil Harman <phil at pharman.org> wrote:
> Hi Erik,
> 
> >
> > I'm recently getting into this too, and one of the reasons I joined is so
> > that I would not have to hear transmitted signal be described as "audio
> > data".  I've already been told that the transmit bandwidth using Ozy is
> > ~150
> > KHz, will Metis permit a wider signal capability?
> 
> I'm not sure I totally understand your question.  The data rate of the I
> and Q signals from the PC to Ozy/Magister/Metis is currently 48ksps.  That
> means the the maximum audio signal bandwidth can be 24kHz.
> 
> By altering the parameters of the interpolating filters on Penelope you
> can increase the bandwidth of the transmitted signal. From memory the DUC
> has a 1dB point at 5kHz.
> 
> You can increase the data rate up to the limits of the hardware (i.e. USB2
> or Gigabit), its just a S.M.O.P.  (Simple Mater Of Programming).
> 
> Does that answer your question?
> 
> 73 Phil...VK6APH

--
Jeremy McDermond (NH6Z)
Xenotropic Systems
mcdermj at xenotropic.com




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