Forum: GNU Radio Time difference of two receivers

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Yong J. Chang (Guest)
on 2009-03-17 00:10
(Received via mailing list)
Hi all,

Now I'm having interesting observation. I have three USRP and RFX2400
and
I'm testing broadcast ( 1 transmitter and 2 receivers). I hooked the
oscilloscope probes up right after AD8347-out (pin 4,3) in RFX2400
board.

Although the two receivers are located very closely, there is a relative
random delay between two received signal ( +-125ns ) . I think that they
are
the same. I cannot understand why they are different.

is there any clue?

Thanks in advance!
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Johnathan C. (Guest)
on 2009-03-17 16:20
(Received via mailing list)
On Mon, Mar 16, 2009 at 3:09 PM, Yong J. Chang 
<removed_email_address@domain.invalid>
wrote:

> Now I'm having interesting observation. I have three USRP and RFX2400 and
> I'm testing broadcast ( 1 transmitter and 2 receivers). I hooked the
> oscilloscope probes up right after AD8347-out (pin 4,3) in RFX2400 board.
>
> Although the two receivers are located very closely, there is a relative
> random delay between two received signal ( +-125ns ) . I think that they are
> the same. I cannot understand why they are different.

How are you measuring the delay?  What are you triggering the
oscilloscope on?

Try connecting the transmitter to the receivers through coax, using at
least 30dB attenuation and a splitter, to see if there is a
difference.  It's possible you are seeing "random" multipath delays
due to reflectors in your environment, though 125 ns sounds rather
high for this.

Johnathan
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