Re: [Discuss-gnuradio] USRP for Radioastronomy

[Matt Ettus]

> What kind of avg_alpha were you using on the FFTs? 

.001


How does one interpret
>   your DDC frequency?  

The signal we wanted was at 1420.4 MHz.  The downconverter they had
there had a 1320 MHz LO.  That put the H line at 100.4 MHz.  Since the
amplitude out of the test port we were using was very low, I decided to
use the TVRX instead of the BasicRX.  When you tune the TVRX to 100.4
MHz, then 100.4 MHz appears at 5.75 MHz in the baseband, and that gets
sampled by the ADC.  The DDC was set to -5.75 MHz to move that down to
DC, and then that was sent over the bus.  The PC decimated and did an FFT.

Were you downconverting to move the DC spur away from
>   the real data, or something less obvious?

See above

> Was this with the dish tracking the galactic center, or was it a drift scan?

It is a drift scan, and the various pictures are of different parts of
the spiral arms of the galaxy.  We weren't really pointing at anything
in particular.

Matt