Re: [Discuss-gnuradio] lowest power of the signal that LFRX can receive

[Yan Nie]

On 03/15/11, Alexandru Csete  <address@hidden> wrote:
> 
> On Wed, Mar 16, 2011 at 1:07 AM, Marcus D. Leech <address@hidden> wrote:
> >> Dear all,
> >>
> >> What is the lowest power of the signal that LFRX can receive?
> >>
> >> Really appreciate any of your help
> >>
> >> Yan
> >>
> > The LFRX has almost no gain, so you're limited by the noise floor of the
> > ADC.  In the USRP2, you can probably reliably detect
> >  signals down to about -60dBm or so.  In the USRP1, you need somewhat more
> > signal, about -50dBm or so.  But those are
> >  ballpark numbers.  But it depends on the details, and what kind of signals
> > you're trying to detect, and whether you want to
> >  demodulate them, or merely detect their presence, etc.
> 
> Using a signal generator I could measure the "CW sensitivity" down to
> about -90 dBm. Using a 2 kHz filter this produced a tone clear enough
> for me to decode morse code. With a tuned vertical antenna ~10 meters
> long, I get very good reception of AM broadcasting and ham radio
> traffic around 7 MHz. I was using USRP1.
> 
> Alex

Really appreciate your reply. The signal that is trying to be detected is 
-117dBm, which turns out a larger amplifier is need in my case. 

I have another question really need your help: how to corresponds the amplitude 
set by program to the Vp-p of the front end output of LFTX? Also the same 
question with receiver side, how to corresponds the amplitude to the received 
signal Vp-p. The amplitude at transmitter side is set by the program and at 
receiver side the amplitude is the one of the signal after DDC.

Really appreciate your help

Yan