Peak in FFT

GNU Radio
1

Hi all!

I use my usrp without antenna. I just want to meassure the noise but,
at 0Hz has always a peak.

I saw that, this was a probleme in the past also, but i didn’t found
the solution.

Attached picture:

http://img4.imageshack.us/img4/2493/messung11.png

What did I wrong?

Best Regreads: Gergely

2

Kóczián Gergely wrote:

http://img4.imageshack.us/img4/2493/messung11.png

What did I wrong?

What daughterboard are you using?

Matt

3

Kóczián Gergely wrote:

Hi all!

I use my usrp without antenna. I just want to meassure the noise but,
at 0Hz has always a peak.

I saw that, this was a probleme in the past also, but i didn’t found
the solution.

Attached picture:

http://img4.imageshack.us/img4/2493/messung11.png

What did I wrong?

Best Regreads: Gergely
I get the same problem. What I ended up doing offsetting the RX tune
freq, then shifting back the same amount using a frequency translating
filter. no spike!

4

On Thu, Nov 5, 2009 at 10:25 PM, Matt E. [email protected] wrote:

Attached picture:

http://img4.imageshack.us/img4/2493/messung11.png

What did I wrong?

What daughterboard are you using?

Matt

From the attached screen shot it looks like you are using a LFRX
daughterboard. Do you have 50ohm output impedance from your source?
You can try terminating your channel with a 50ohm terminator and see
if the peak goes away.

Karthik

5

Yes I use LFRX.

Thanks the suggestion, i will try.

2009/11/7 Karthik [email protected]:

6

Kóczián Gergely wrote:

Yes I use LFRX.

Thanks the suggestion, i will try.

2009/11/7 Karthik [email protected]:

Did you ever fix your problem?