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Today's Topics:
1. Re: B205mini Frequency Accuracy (carry chen)
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Message: 1
Date: Sun, 28 May 2017 08:17:24 +0000
From: carry chen <[email protected]>
To: "[email protected]" <[email protected]>, Marcus
M?ller <[email protected]>
Subject: Re: [USRP-users] B205mini Frequency Accuracy
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Marcus,
Thanks for your tips!
I play with sdr lte tdd bts this days.
lte bts need sync with each other,its is say:the frames of each bts need align.
when I make my bts frame align with real lte tdd base station, I find that it
become unalign very quick! the start sample of my bts frame is drift from
start samples of real bts frame.
So I think the clock is not good enough for lte tdd bts.
Thank you very much!
Best regards,
Carry
???: Marcus M?ller via USRP-users
????: 5?25???? 04:12
??: Re: [USRP-users] B205mini Frequency Accuracy
???: [email protected]
Hi Carry,
I'd still light to highlight the question the other Marcus asked:
It's not very usual that an application needs such a high-quality clock source.
Since no two oscillators in this universe are exactly the same, all practical
receivers have some way to account (and often: correct) a clock offset! So,
before you spend money, ask yourself if your application wouldn't need to
implement something like that, anyways!
So: what is the reason the on-board oscillator isn't good enough for you?
Best regards,
Marcus
On 24.05.2017 21:25, carry chen via USRP-users wrote:
Steven,
Very?appreciate?for you message!
I will try it!
???nks all!
Carry
From: Steven Knudsen <[email protected]><mailto:[email protected]>
Sent: Wednesday, May 24, 2017 11:46:05 AM
To: carry chen
Cc: [email protected]<mailto:[email protected]>; Jason Matusiak; USRP-users
Subject: Re: [USRP-users] B205mini Frequency Accuracy
There are many options for 1 PPS or 10 MHz clock sources, it all depends on
where you live and how you want to get one.
You can, for example, get a GPS module from ublox, AdaFruit, SparkFun, or
Amazon and make your own SMA terminated cable to connect to the REF input on
the mini. You need to be sure that the signal levels are within spec as show on
the B200mini schematic, for example. It may mean making a level translating
circuit. Normally you want to match the 50 Ohm impedance, but it?s not critical
it?s exact as long as the thresholds are met.
https://files.ettus.com/schematics/b200mini/
Personally, I love my Octoclock G :-)
There is support for external sources in the UHD and there are example programs
in the source to show you how..
Good luck,
steven
Steven Knudsen, Ph.D., P.Eng.
www. techconficio.ca<http://techconficio.ca>
www.linkedin.com/in/knudstevenknudsen<http://www.linkedin.com/in/knudstevenknudsen>
Von einem gewissen Punkt an gibt es keine R?ckkehr mehr. Dieser Punkt ist zu
erreichen. - Franz Kafka
On May 24, 2017, at 12:25, carry chen via USRP-users
<[email protected]<mailto:[email protected]>> wrote:
Thanks!
I see b205mini have three sma port, one ??X/RX , one RX2, and one REF, does
external clock source connect to REF sma port?
Can you give me some tips where to buy the external clock source ?
Does external clock source connect to port direct and the uhd is support direct?
Have some body do that ?
Thank you very much again!
From: [email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>
Sent: Wednesday, May 24, 2017 8:33:18 AM
To: Jason Matusiak
Cc: carry chen; [email protected]<mailto:[email protected]>
Subject: Re: [USRP-users] Fw: B205mini Frequency Accuracy
Yes, sorry if I created any confusion.
The 'mini' series have no provision for an on-board GPSDO, like their big
brothers do. You'd need to use an external clock source, and use the sync
input on the 'mini' series.
On 2017-05-24 10:45, Jason Matusiak via USRP-users wrote:
Carry, What I think Marcus means, is that you could use the sync/clock port on
the mini to get better accuracy. There is no way to add on a GPSDO directly.
On 05/24/2017 01:08 AM, carry chen via USRP-users wrote:
Thanks, mleech,
But I check the ettus website, only B210/B200/E3xx have GPSDO interface,
Can B205mini do that?
Can some body recommend some GPSD or OCXO Product use for B205mini ?
Thank you very much!
Carry
From: [email protected]<mailto:[email protected]>
<[email protected]><mailto:[email protected]>
Sent: Tuesday, May 23, 2017 12:04 PM
To: carry chen
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [USRP-users] B205mini Frequency Accuracy
The usual way to do that is to use an external reference oscillator that is
better than the clock that is on-board.
For example a GPSDO, or an external 10MHz OCXO source, etc.
On 2017-05-23 14:58, carry chen via USRP-users wrote:
Hi,list
I check the b205mini datasheet and see the frequency accuracy is ?2.0 ppm,
Can I change the clock to get better frequency accuracy?
Thank you very much!
Carry
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