Milos, Early AM for me….disregard what I just said…had a pre-coffee moment…LO not present in signal chain at that point…doh! > On Jan 3, 2019, at 7:27 AM, Milos Milosavljevic <milos_m...@hotmail.com> > wrote: > > Thank you Ian. > > Apologies, we are using the SBX not WBX (that was a typo from my side). I > believe that SBX also has TX baseband filters. > > Regardless, sorry, but what did you mean by offsetting the LO spur's into > those filters? Via tune_request_t? > > Thanks > Milos > > From: Ian Buckley <i...@ionconcepts.com <mailto:i...@ionconcepts.com>> > Sent: 03 January 2019 15:16 > To: Milos Milosavljevic > Cc: usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>; Marcus D. > Leech > Subject: Re: [USRP-users] Unexpected spurious from N200 > > Milos, > FWIW WBX includes TX baseband filters of 40MHz bandwidth. LO offsetting your > LO spur’s into those should suppress this. > -Ian > >> On Jan 3, 2019, at 3:48 AM, Milos Milosavljevic via USRP-users >> <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote: >> >> Thank you Marcus. Much appreciated. >> >> I think I do understand why would I see some sort of phase noise if DUC >> doesnt work but the only one bit of information that i am missing (i am sure >> it is a silly question) is why would the offset be ignored if tune_request_t >> is typcasted to float? Btw, just please note though that if a source is just >> a constant (so basically there is no modulating signal) the spectrum is much >> cleaner with float typcasting of tune_request then no typecasting. >> >> And lastly, since typecasting to float is no go, do you know how I can >> reduce the spurs when i just use uhd.tune_request(f,lo_offset) without using >> external filetring? I tried mode_n=integer but it doesnt help. Those spurs >> are like 20MHz from the carrier and are destroying our amp (due to >> reflections). 🙁 >> >> Thanks >> Milos >> >> From: USRP-users <usrp-users-boun...@lists.ettus.com >> <mailto:usrp-users-boun...@lists.ettus.com>> on behalf of Marcus D. Leech >> via USRP-users <usrp-users@lists.ettus.com >> <mailto:usrp-users@lists.ettus.com>> >> Sent: 03 January 2019 05:36 >> To: usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> >> Subject: Re: [USRP-users] Unexpected spurious from N200 >> >> On 01/02/2019 08:06 PM, Milos Milosavljevic via USRP-users wrote: >>> Dear All, >>> >>> I was wondering if somebody could clarify a couple of issues that I have >>> with the UHD and N200 USRP. I am using the latest version of the software. >>> >>> I am generating a single tone to be transmitted with N200 (WBX board) using >>> uhd_siggen as: >>> >>> uhd_siggen -g 15 -s 500000 -m 0.5 -f 402000000 --lo-offset 10000000 -x >>> 50000 --sine >>> >>> 1) I can see quite a strong spurs at 10MHz and 20MHz freq offset from the >>> carrier? (I am not using any external filtering) >> Define "quite strong". >> >> >>> >>> 2) If I modify the siggen to use float((uhd.tune_request(f,lo_offset)) >>> instead of just uhd.tune_request(f,lo_offset) the signal with constant >>> source is much cleaner. However, if I modulate the carrier with a sine >>> source another set of spurs appear very close to the carrier. This is not >>> though the case when float is not used (but spurs at 10 and 20MHz are still >>> present). >>> >>> Why does the float with tune_request make such a big difference? >> Well, looks like you're casting a tune_request_t to a float, which means >> that the offset instruction will likely get ignored, which changes >> whether the DUC comes into play or not. >> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
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