Re: [Openbts-discuss] OpenBTS Clock

[Alexander C. <ale...@gm...>]

Samuel,

26.03.2012 22:26 пользователь "Samuel Liverpool" <sam...@ho...>
написал:
>
> Dear List,
>
> I wrote some time ago about some issues I was having with the GPSDO unit
with my N210. I had similar problems to those raised by others with phones
not camping and not reconnecting once they went out of range etc - these
were pointing to the clock. I had gotten linux; GNU C++ version 4.6.1;
Boost_104601; UHD_003.004.000-122b947
>
> -- Opening a USRP2/N-Series device...
> -- Current recv frame size: 1472 bytes
> -- Current send frame size: 1472 bytes
> -- Found a Jackson Labs GPS
> -- Setting references to the internal GPSDO
> -- Initializing time to the internal GPSDO
>
> UHD Warning:
> The hardware does not support the requested RX sample rate:
> Target sample rate: 0.270833 MSps
> Actual sample rate: 0.271739 MSps
> kal: Scanning for GSM-900 base stations.
> chan: 40 (943.0MHz + 3.422kHz) power: 139281.38
> chan: 59 (946.8MHz + 3.410kHz) power: 16115.09
> chan: 122 (959.4MHz + 3.528kHz) power: 12133.84
>
> These issues were not resolved so I have the following questions
>
> Is it necessary to have the GPS antenna connected and locked to a GPS
signal for the reference clock to work with OpenBTS?

I know nothing about your GPSDO, but it's logical to assume that GPS lock
I'd required for it to assume correctly. As Thomas mentioned, OCXO usually
have  better stability then TCXO. But the initial offset is often huge. So
you usually have to lock it before the use. Then you may be able to
disconnect antenna, but you have to check this with your GPSDO datasheet.

> Does the ClockTamer clock work well with the N210 and if so which one is
better?

I don't know anything about your GPSDO, so it's hard to guess. What I could
say for sure it's that ClockTamer is good enough to recalibrate it about
one a month if you use it indoors. And you could recalibrate without GPS
using kal only.

Sent from my Android device.

--
Regards,
Alexander Chemeris
CEO, Fairwaves LLC
http://fairwaves.ru