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From: | Marcus D. Leech |
Subject: | Re: [Discuss-gnuradio] lowest power of the signal that LFRX can receive |
Date: | Wed, 16 Mar 2011 09:27:06 -0400 |
User-agent: | Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 |
On 16/03/2011 1:37 AM, Yan Nie wrote:
The only way to do this is to measure and calibrate. The USRP+Daughtercard family aren't precision measurement instruments. There's significant variability in the analog components. So, the only way to do is to use already-calibrated measurement tools, and construct your own calibration tables.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 YanThe 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. AlexReally 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
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