Re: [Discuss-gnuradio] New external clock board for USRP

[David Burgess]

Alexander -

We expect to be able to get VCTCXOs in modest volumes for less than  
$30.  The TCXO we are using now is $23.  Most of the cost of the  
clock doubler board is the labor for getting it assembled locally in  
small batches.

When/if the FPGA firmware gets fixed, we can use a 26 MHz part  
without a doubler, which would reduce the cost further.

-- David


On Sep 29, 2009, at 2:02 AM, Alexander Chemeris wrote:

> Hi David,
>
> Could you elaborate why do you consider this approach? While we see  
> some
> advantages of it in terms of lower noise, it looks like our approach
> is few times
> cheaper with reasonable noise and stability figure. If we  
> understood correctly,
> bare VCTCXO chip costs $230 on DigiKey, while in our case discrete  
> unit with
> all accessories produced in low volume costs about $100.
>
> On Mon, Sep 28, 2009 at 22:06, David Burgess  
> <address@hidden> wrote:
> > One of the approaches we are considering for OpenBTS is to use a  
> > VCTCXO with
> > the control voltage taken from one of the D/A outputs of the FPGA,  
> > with LOTS
> > of low-pass filtering, of course.
> > This would not give a wide range of frequencies, but would allow  
> > precise
> > frequency calibration through the existing libusrp APIs.
> >
> > On Sep 28, 2009, at 9:00 AM, Tim Pearce wrote:
> >
> > In terms of integrating more tightly with the USRP/GnuRadio
> >
> > You could (maybe) just use the SPI pins and one of the digital IO  
> > lines as
> > the enable (the ATMega8 running as a slave)
> >
> > That way theres functions to communicate with the chip already  
> > built in you
> > just need to define the various commands etc?
> >
> > Tim.
> >
> >
> > David A. Burgess
> > Kestrel Signal Processing, Inc.
>
>
>
> --
> Regards,
> Alexander Chemeris.
>
> SIPez LLC.
> SIP VoIP, IM and Presence Consulting
> http://www.SIPez.com
> tel: +1 (617) 273-4000


David A. Burgess
Kestrel Signal Processing, Inc.