Hi John, I'm a bit confused. You're using the WBX, correct? The WBX can not go down to 3.something MHz, that's outside its frequency range. You should be getting warnings about that when trying to tune there; you're most probably looking at the signal at the lowest frequency that the WBX can do.
The other things you said were a bit questionable, but I'd prefer to discuss them when I understand where the signal you're interested in actually lies. Best regards, Marcus On 06/05/2015 01:41 AM, John Petrich wrote: > > Oh, thanks Marcus. So, you are saying that there is no way to shift > the DC spike at baseband. Got what you are saying. As a practical > matter at baseband, I shift the DC point by specifying a frequency in > the USRP higher than the target frequency, and then specify a > frequency in the Xlating filter that is lower than the desired > frequency. Ends up shifting the DC spike away from the desired > frequency. > > > > However, with my WBX board, what command would you suggest in the USRP > Source center frequency parameter field? > > > > Thank you very much for your time and help. > > > > Regards, > > John Petrich > > > > *From:*Marcus Müller [mailto:[email protected]] > *Sent:* Thursday, June 4, 2015 3:33 PM > *To:* John Petrich; GNURadio Discussion List > *Subject:* Re: [Discuss-gnuradio] Move USRP LO with USRP sink block? > > > > You can request that UHD tries to get the LO offset you request as > close as possible, but because the LO synthesizers used on the > USRPs/daughterboards (what are you using, by the way?) can only > synthesize a discrete set of frequencies, not everything is possible. > Now, I just realized you tried to tune a daughterboard to 3MHz (I > misread and thought you'd try to tune to 3GHz). There's no > daughterboard that goes that far down, because that's really just > baseband. > So I have to assume that you're using LFRX or BasicRX, which don't > have mixers, so the LO frequency is always 0 and the digital shifting > is always the center frequency you ask for. > > Best regards, > Marcus > > On 06/05/2015 12:20 AM, John Petrich wrote: > > Marcus, > > > > Yes, could you help me with a specific command for the properties > field: I want a rx frequency of 3.545 MHz with an LO offset of > 50e3 Hz. > > > > Thank you, > > John Petrich > > > > *From:*Marcus Müller [mailto:[email protected]] > *Sent:* Thursday, June 4, 2015 2:41 PM > *To:* John Petrich; GNURadio Discussion List > *Subject:* Re: [Discuss-gnuradio] Move USRP LO with USRP sink > block? (was: Re: question per your 2/10/15 post on Ruby Forum) > > > > Hi John, > I'm a bit confused; which discussion is this from? > Ruby-Forum is not actually the platform we use, they just "mirror" > the GNU mailing list archives (I don't really know why they do > that -- we don't have anything to do with them). I'd recommend > joining that mailing list personally [1]. > > Regarding your question: > 10kHz is very small. Possibly, the closest possible physical LO > frequency is still the one you'd have if you didn't shift. Try > increasing 10e3 to something that is out of the band that you want > to observe; for example, if you're using a sampling rate of 10e6, > try 11e6. The only important thing is that the whole observed band > stays within the analog bandwidth of your USRP (B2x0) or the > daughterboard used (modular USRPs). > > Best regards, > Marcus > > [1] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > On 06/04/2015 11:26 PM, John Petrich wrote: > > Marcus, > > > > I cannot get the DC component to shift using this command in > the USRP _Source_ block properties: > uhd.tune_request(3.545e6,10e3) What am I missing? > > > > Thank you in advance, > > John Petrich > > > > *Re: Move USRP LO with USRP sink block?* > <https://www.ruby-forum.com/topic/6873252#1167936> > > D17685d174fee4ca258c75cce7bc2202?d=identicon&s=25Marcus Müller > (Guest) > > on 2015-02-10 20:10 > > (Received via mailing list) > > Well, you nearly already are doing this! > > just use "uhd.tune_request(...,...)" where you'd set the TX frequency > > normally in the USRP sink's properties dialog. > > > > > > >
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