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

From: Alexander Chemeris
Subject: Re: [Discuss-gnuradio] New external clock board for USRP
Date: Tue, 29 Sep 2009 13:02:15 +0400

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.

Alexander Chemeris.

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