Unwanted signal transmitted RFX900

Hi all,

Making some tests I have found that my system (USRP + RFX900) transmits
an important signal (it seems a tone) without any application running,
just when I plug the power source it transmits this unwanted signal. I’m
working at the GSM900 downlink frequency band (between 935 and 960 MHz)
and the signal appears close to the upper side of this band, around
959,6 Mhz.

My system makes an spectrum sensing for that band and it locates the
present signals, so it produces an error because it detects this
undesired signal generated by itself. Any idea of the problem? Any
solution?

Thanks!

On Thu, 2011-01-20 at 12:48 +0100, Paco Quiñoy wrote:

My system makes an spectrum sensing for that band and it locates the
present signals, so it produces an error because it detects this
undesired signal generated by itself. Any idea of the problem? Any
solution?

Paco,

This is likely to be the 15th harmonic of the USRP’s 64MHz sample clock
(64e6*15=960e6). It may get better after the USRP is initialized (run
uhd_usrp_probe or any other application after power-up). The AD9862
tends to come up in a weird state.

–n