Frequency Mismatch between TX and RX


I’m newbie to Gnuradio. I tried a simple example using USRP 1.0 with the
help of Gnuradio-companion(GRC). I’m using RFX 2400 daughter boards.

I just tried to transmit cosine wave of 20 khz. But on the receiver side
i was getting 30 khz cosine wave…its happening with all the
frequencies. And the this extra frequency is also varying (sometimes
10k, sometimes 7k, 8k).

Type of Cosine : Complex
Frequency : 2.45 GHz (Offset ‘O’)
Sampling rate : 250 k samples/sec

Plz help me, why this is happening…and suggest some ideas to deal
with this problem.


from previous posts, i understood that it happens because of
non-idealities of crystal which generates frequencies.

Can someone suggests how to handle this offset in grc ?