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

From: David Burgess
Subject: Re: [Discuss-gnuradio] New external clock board for USRP
Date: Tue, 29 Sep 2009 11:16:57 -0700

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?


David A. Burgess
Kestrel Signal Processing, Inc.

Alexander Chemeris.

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David A. Burgess
Kestrel Signal Processing, Inc.

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