USRP + wbx-fe-simple board + WA5VJB antenna

Dear gnuradio discussion list,

Currently I’m experimenting with the USRP with the wbx-fe-simple board
rev 4, wbx-board rev 2 and the WA5VJB antenna.
The installation of uhd and gnuradio worked fine and I’m able to run the
dialtone.grc example.

However when I execute:

Sudo uhd_fft -f 401M -g 26 -a TX/RX

I get the GUI with some wave on it (and no errors in the terminal).
When I disconnect the antenna from the USRP the wave does not change,
also on other frequencies the same procedure does not show any
deviation. The wave however changes slightly when moving to the 801.11
(WIFI) and the terminal prints a 0 to the screen.

This all gives me the feeling that the antenna is not really working. (I
expected not to see a signal on 401Mhz since this frequency is for
medical hardware which is not available in the room).

Did somebody experienced the same problem / has a solution for this

Great tnx in advantage!

Kind Regards,
Jeroen Slobbe