[hpsdr] Mercury Rising!

[Phil Harman]

All,

Through the generosity of Phil N8VB I have access to a pair of LT2208 evaluation boards.  These consist of a DC854C board that contains the LT2208 and a DC718B board that provides a USB 1 interface to the PC.  See www.linear.com for more details on these boards. 

The evaluation boards enable various performance measurements to be made.  The screen shot at 

<http://www.hamsdr.com/personaldirectory.aspx?id=284>

is of the LT2208 being clocked at 100MHz from a low noise crystal oscillator. The FFT shows the spectrum from 0 - 50MHz using 4096 FFT bins and a Hann windowing function. The signal input is at 25MHz from my HP8640B signal generator at +10dBm.  The input amplifier in the LT2208 is set for maximum gain which gives an input overload of  1.5v  and a noise floor of   -86dBm in the above FFT bandwidth.  

Sweeping the signal generator over 0 - 50Mhz does show a significant number of spurious signals but I have no idea how LT are doing the FFT so its a little early to speculate.  Setting the input frequency to an integer of the clock frequency yields a spurious free display.

At this stage all is looking good. In addition to a possible front end for the HPSDR then spectrum analyser and digital oscilloscope options look viable. 

Next I need to connect the DC854C board to an FPGA so I can do tests in a narrower bandwidth.  Given the functions that I will need I'm not sure this will fit in the Xylo board so further development may have to wait for the Ozy board. I have the Verilog code running in simulation mode for the NCO and multipliers and am about to start designing the CIC filter. 

Any suggestions for additional tests to do using the evaluation boards are welcome. 

73's Phil... VK6APH 



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20060605/5da74301/attachment-0004.htm>
-------------- next part --------------
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.394 / Virus Database: 268.8.1/355 - Release Date: 2/06/2006