Re: [Discuss-gnuradio] USRP tuning time

[Mat Mat]

hey man,

many many thanks for the detailed reply! Based on it, I decided to 
achieve frequency hopping not by changing the centre frequency of the 
USRP, but by multiplying my signal with a sine of a certain frequency 
offset and then transmit that signal over the USRP with a fixed USRP. 
Unfortunately, a new problem has arisen. you can see my flowgraph 
attached

I want my signal to be transmitted on 5.804GHz. to this end, the centre 
frequency is set to 5.799GHz, and the signal that I wish to transmit is 
multiplied with a sine wave of 5MHz. (I'm storing everything as a file 
before transmitting, as things are otherwise too slow). The problem now 
is that when I transmit the signal over the USRP, it is not transmitted 
on 5804 MHz but on approx. 5802 MHz. Furthermore, this error appears to 
become bigger with bigger frequency offsets: When I want the signal to 
be transmitted with 20MHz offset to the centre frequency of the usrp 
(thus using a sine wave of 20MHz), the difference between the intended 
signal frequency and the true signal frequency is almost 10 MHz!

Am I doing anything wrong here??

kind regards and thanks so much,
Mat

Attachments:
http://www.ruby-forum.com/attachment/10982/modulator.jpg


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