OpenBTS - March 29/30 [Clock Issues]

We've been having a hard time getting our 52MHz clock working. On top of full time classes and other commitments, both our project group and instructor have been falling behind in troubleshooting the issue. We hope to finish strong and pump out more vids in April!

Category:

Science & Technology

Tags:

• SAIT
• ITTS
• OpenBTS
• oscilloscope
• 52MHz
• 64MHz
• USRP
• RFX900
• GSM
• GNU Radio

[blanchae]

It is not possible to change the onboard 64 MHz clock chip. There are no pin compatible and physical compatible chips available. Your only choice is to use an external 52 MHz clock source. I purchased the 52 MHZ clock source to the specs that were provided by the USRP board manufacturer and created the piggyback board. Then found out that the given USRP specs were wrong and I wasted 8 weeks purchasing the wrong part. Bummer...

[010675dario]

How did you manage to fix the 52 Mhz clock? In my case i purchased to a provider in China a lot of 52 MHz chip. Once installed on the usrp/wbx+gnuradio+kal i was able to scan and find many BTS antennas on all the gsm bands (850,900 1800 1900). My openbts start normally but my unlocked cellphones are not capable to find the test network.

Finally i had to purchase the external clock generator from fairwaves. (Clocktamer)

Please can you share the design of your PCB 52 MHz clock generator?

[andiegurgel]

I use an oscope and a frequency standard to verify and tune the clock accuracy - just trigger to the waveform of the frequency standard and try to manage the waveform of the to run through as slow as possible (same trick they used with some record players in the 80ties)

This works also pretty fine.

[roncho]

hi!.. I was wondering if its not possible to change 64Mhz cristall for an 52Mhz one inside USRP board.. did you try this?