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sergey kostanbaev sergey.kostanbaev at gmail.comOn Thu, Jul 19, 2012 at 6:10 PM, Andrey Sviyazov < andrey.sviyazov at fairwaves.ru> wrote: > Hi all. > > I've found spurs on the LO noise plot at ~33kHz and ~66kHz offset when > GPS antenna used and position locked. > This spurs begin grow up when GPS just near to lock position and after > locking spurs stopped to grow as you can see at picture. > If thereafter GPS disconnected then noise coming back to normal plot. > I think that it is result of 32768Hz clock in the GPS module EB-230, but > can't understant how it can impact to 26MHz clock or VCO. > As another idea it can be caused by continues GPS correction lead to DAC changes to the VCTXCO. > Please tell me something who know. > > Thomas. > Was GPS antenna connected when noise measured like on the picture which > you sent us (also attached here)? > I would to know because of anomal peak near to 30kHz offset too. > > Best regards, > Andrey Sviyazov. > > > > 2012/7/19 Andrey Sviyazov <andrey.sviyazov at fairwaves.ru> > >> Sorry, that was meant to be sent to the mailing list :) >> >> Best regards, >> Andrey Sviyazov. >> >> ---------- Forwarded message ---------- >> From: Andrey Sviyazov <andreysviyaz at gmail.com> >> Date: 2012/7/18 >> Subject: LMS TxLO noise >> >> Hi Thomas. >> >> Here forwarded my last e-mail with noise plots when I stopped work around >> it at first time, please see below. >> >> Please try to play around Tx PLL charge pump current (register 0x16) for >> better RMS phase stability. >> I think we should reach 1 degree or below. >> >> Alexander gave me the second UmTRX board and after checking and fixing >> all known hardware issues<http://code.google.com/p/umtrx/issues/list?can=1&q=&colspec=ID+Type+Status+Priority+Milestone+Owner+Summary+Modified&cells=tiles>I've got roughly the same LO noise plot. >> Possible Robin had no time to fixing all of our issues, so check them all >> please. >> And also check please what type of TCXO installed on your board. >> >> Best regards, >> Andrey Sviyazov. >> >> ---------- Forwarded message ---------- >> From: Andrey Sviyazov <andreysviyaz at gmail.com> >> Date: 2012/4/13 >> Subject: Re: LMS TxLO noise >> >> Hi all. >> >> There is progress with LMS PLL :) >> Pictures are attached here. >> t was discovered that 80 kHz spurs come from Ethernet, or rather from the >> ET1011. >> I unknowingly put the choke between transistor of 1V regulator and >> analog power 1V. >> As a result, the regulator has become unstable and oscillated 80 kHz with >> amplitude of 200 mV, which climbed into the LMS PLL. >> To correct this problem L46 should be replaced by jumper on all alfa >> version PCB's. >> >> Also I just played with current in the PLL loop, shown on the picture for >> clarity. >> Proved to be the optimal current 1,9 mA (you should write 0x93 in the >> register of 0x16). >> But, I think, for the RxPLL will be better use of the current 2.4 mA, >> because the nearest noises more important for Rx (you should write 0x98 in >> the register 0x26). >> >> Best regards, >> Andrey Sviyazov. >> >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120719/9a0a4239/attachment-0001.htm>