[Discuss-gnuradio] frequency offset of USRP

[Sl Peng]

Hi all:
My task is to use the USRP to down convert the GPS L1 channel to
baseband signal.
I have some problems with the carrier offset of the DBS_RX
daughterboard.
When I set f_l0 of the DBS_RX daughterboard to be 1575.42e6 which is the
center frequency of GPS L1 signal, I found the real frequency in the
tune(double _freq) function was 1575.5e6. So there is 80000 hz offset. I
want to know what the output of DBSRX daughterboard is. What is the
effect of this offset to my input signal?

Next, I need to down convert the output signal of the daughterboard. Fox
example, I want to down convert it to 1.5M hz. Then, what should I do?
I think I should use this function:
usrp_standard_rx: set_rx_freq (int channel, double freq).

What is the input value of freq?

Any suggestions? Thanks a lot!
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