# B200 clock calibration **URL:** \ **Category:** GNU Radio\ **Created:** [May 14, 2014, 12:14pm UTC](https://www.ruby-forum.com/t/b200-clock-calibration/241132 "2014-05-14T12:14:00Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [May 14, 2014, 12:14pm UTC](https://www.ruby-forum.com/t/b200-clock-calibration/241132/1 "2014-05-14T12:14:00Z")
I try to get B200 to work with OpenBTS and I see some frequency offset in the internal reference clock. Does anyone know if the numbers I get from kalibrate, could cause phones not to be able to register to OpenBTS? What is the quickest and the cheapest way fix a problem with a clock? I think B200 has TCVCXO, so is there a way to write some tuning voltage offset to correct the frequency? Do a clock calibration? Does anyone know the exact part nr of TCVCXO mounted in B200? UHD Warning: The hardware does not support the requested RX sample rate: Target sample rate: 0.270833 MSps Actual sample rate: 0.271186 MSps kal: Scanning for GSM-900 base stations. chan: 19 (938.8MHz + 1.915kHz) power: 2812.45 chan: 26 (940.2MHz + 1.900kHz) power: 14595.33 chan: 33 (941.6MHz + 1.913kHz) power: 18358.13 chan: 58 (946.6MHz + 1.930kHz) power: 9563.79 chan: 114 (957.8MHz + 1.957kHz) power: 1872.65 Using GSM-900 channel 19 (938.8MHz) average [min, max] (range, stddev) - 1.896kHz [1855, 1943] (88, 19.746572) overruns: 0 not found: 92 ---
**Author:** ![rlorimor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/96bed5/32.png) [@rlorimor](https://www.ruby-forum.com/u/rlorimor)\ **Post date:** [May 14, 2014, 12:17pm UTC](https://www.ruby-forum.com/t/b200-clock-calibration/241132/2 "2014-05-14T12:17:42Z")
On 14.05.2014 12:12, Robert L. wrote: > Actual sample rate: 0.271186 MSps > Robert, as long as you see this warning, you’ll get offsets. I don’t know where or how kal sets up the master clock, but you should put in a master\_clock\_rate=13e6 somewhere in there. M ---
**Author:** ![rlorimor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/96bed5/32.png) [@rlorimor](https://www.ruby-forum.com/u/rlorimor)\ **Post date:** [May 14, 2014, 2:33pm UTC](https://www.ruby-forum.com/t/b200-clock-calibration/241132/3 "2014-05-14T14:33:40Z")
Hi, > I > think B200 has TCVCXO, so is there a way to write some tuning voltage offset to > correct the frequency? There is no way to trim the TCVCXO manually. It’s included in the loop of a PLL for external locking but you can’t control it directly. It seems that manual control was considered because adding a resitor can connect the control line to an aux DAC of the ADI, however it seems that the voltage might not be compatible and so you’d need external amplification to drive it. (that’s from memory, might be worth rechecking schematics and specs) Cheers, ``` Sylvain ``` ---
**Author:** ![rlorimor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/96bed5/32.png) [@rlorimor](https://www.ruby-forum.com/u/rlorimor)\ **Post date:** [May 14, 2014, 5:45pm UTC](https://www.ruby-forum.com/t/b200-clock-calibration/241132/4 "2014-05-14T17:45:39Z")
On Wed, May 14, 2014 at 6:16 AM, Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > master\_clock\_rate=13e6 somewhere in there. > In this particular case, it’s actually not very important. Kal is > basically performing a tone search and the sample rate used for > internal calculations is the rate returned by UHD. The sample rate can > be almost any value. 2 kHz offset is within tolerance for 1900 MHz. Locking to a stable 10 MHz reference, generally an OCXO or GPSDO, is the recommended approach. -TT ---
**Author:** ![rlorimor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/96bed5/32.png) [@rlorimor](https://www.ruby-forum.com/u/rlorimor)\ **Post date:** [May 14, 2014, 5:49pm UTC](https://www.ruby-forum.com/t/b200-clock-calibration/241132/5 "2014-05-14T17:49:21Z")
On 05/14/2014 11:44 AM, Tom T. wrote: > > master\_clock\_rate=13e6 somewhere in there. > > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) The on-board clock on the B200 is good to about 2PPM, so 2kHz in 1900Mhz is just about right. – Marcus L. Principal Investigator Shirleys Bay Radio Astronomy Consortium > **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org)** > > Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami. ---
**Author:** ![rlorimor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/96bed5/32.png) [@rlorimor](https://www.ruby-forum.com/u/rlorimor)\ **Post date:** [May 16, 2014, 10:27am UTC](https://www.ruby-forum.com/t/b200-clock-calibration/241132/6 "2014-05-16T10:27:37Z")
* * * Discuss-gnuradio mailing list removed\_email\_address@domain.invalid [https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)