[USRP-users] wired issue on usrp receiver side

Marcus D. Leech mleech at ripnet.com
Tue Feb 5 21:02:12 EST 2013

On 05/02/13 08:45 PM, Chenfei Gao wrote:
> Hi all,
> I set up my communication system involving transmitter and receiver by
> two USRP N200s. Unfortunately receiver cannot correctly decode the
> signal so when I was tracking the fc32 data coming in I found a wired
> issue. With transmitter off, I was running receiver only. I found
> there still were a lot of fc32 messages coming in. Is it because there
> were still a lot of data stored in the usrp buffer? And then I powered
> recycle USRP N200 and thought all buffered data should be cleared by
> that way. But when I reconnected USRP running, same things happened.
> Does anybody have the similar situation? I am a newbee to USRP and I
> need help from you.
> Any suggestions would be appreciated.
> Chen
The analog and digital sampling machinery continues to run whether your
signal is being transmitted or not. When nobody
is transmitting on your chosen frequency, the receiver "sees" noise. The
receiver is dumb, it has no way of knowing
exactly what *meaning* is of the samples flowing through it. You impart
"meaning" through the use of demodulators,
etc. But the USRP hardware in and of itself has no way of distinguishing
between "a signal that Chen might be interested
in" and anything else. That's what distinguishes SDRs from other types
of radios, there are, despite their sophistication,
extremely "dumb". But in this apparent stupidity, comes deep, profound

Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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