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Re: [Discuss-gnuradio] Re: question about RFX2400


From: Malihe Ahmadi
Subject: Re: [Discuss-gnuradio] Re: question about RFX2400
Date: Wed, 23 Feb 2011 19:08:22 -0700
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7

Yeah, I mean ref clock. I actually connect a 10MHz sin wave with 15dBm amplitude to two USRP2, one acting as TX and the other one acting as RX. the reason I am using this ref clock is to avoid the frequency offset between the TX and RX (I have been observing about 1MHz offset between the two). But yet there is about 1MHz frequency offset between TX and RX and that is the reason I thought their are not locked to the ref clock. Why would I still observe about 1MHz frequency offset then?

On 2/23/2011 2:32 PM, Ed Criscuolo wrote:
On 2/23/11 4:07 PM, Malihe Ahmadi wrote:
Hi,

I have included this line in my python flowgraph:
|||sink.config_mimo(usrp2.MC_WE_LOCK_TO_SMA)
where sink is: ||sink ||=| |usrp2.sink_32fc()|
but I think USRP2 is not locked to the external reference clock since
when I turn this ref clock generator off, there is no change in the
spectrum of the output of USRP2. My understanding is that if USRP2 is
locked to the ref clock, when I turn the clock off I should see no
signal at the output of USRP2. can somebody please help me with this?
How do I get the USRP2 to lock to the ref clock?


I believe this is a reference clock, not an external clock.  If so,
the USRP would continue to run on its internal clock, which has been
synced to the reference clock.  When the ref clock is removed, the
internal clock would continue to operate, slowly drifting.

@(^.^)@  Ed





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