[USRP-users] Capturing signals at the carrier
Cochenour, Brandon M CIV NAWCAD, 4.5.6
brandon.cochenour at navy.mil
Mon Sep 30 16:47:14 EDT 2013
After some further experimentation...I notice that not all carrier frequencies result in the DC component being removed.
For example....using the N210 with WBX...
At a 50 MHz carrier...I can modulate a single tone all the way down to about 200 Hz with no issue. Between 100-200 Hz...I observe all sorts of weird harmonics. At 100 Hz...everything is fine. Between 1-100 Hz...strange harmonics. And then a 0 Hz...a clear spectral peak at DC.
However at certain other frequencies....I'll get no DC through at all.
I also note that it doesn't matter if I use the TX side of the WBX as my input...or if I try to tune an external source to get as close to the USRP LO as I can. Some center frequencies work. Others don't.
There doesn't seem to be much rhyme or reason as to why certain frequencies work, and others don't. Should there be?
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