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From: | Marcus Leech |
Subject: | Re: [Discuss-gnuradio] RFX-400 RF sensitivity |
Date: | Fri, 24 Nov 2006 23:30:51 -0500 |
User-agent: | Thunderbird 1.5.0.8 (X11/20061025) |
Greg Troxel wrote:
I use a DBS_RX with USRP for radio astronomy. There are a couple of narrowband "birdies" created by the overall receiver system. But I have about 40dB of low-noise gain in front of the DBS_RX, and I can just about detect somebody farting on the space station :-) :-)Is it possible that the high speed digital signaling on the USRP motherboard is significantly reducing the sensitivity of the daughter-board? Yes, it is possible. You should examine the circuit diagram and determine what kind of noise floor you would expect, given the NF of the first RF amplifier and losses before it; your experiment is not enough evidence to conclude that there's any such interference.
For my application, I was worried about noise created by the underlying system, but with enough low-noise gain "out front", it doesn't seem to matter much. What *does* matter in my application is gain stability, which is why I have the USRP+DBS_RX in a temperature-controlled environment.
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