I use an USRP1 together with gnuradio/GRC and would like to transmit an
signal, abt. 1 MHz bandwidth at 433 MHz. The FFT display block within
shows the power mask as expected, a flat line over the bandwidth, and
drops at both ends. What a real spectrum analyzer at the output shows is
something totally different, like a Gaussian distribution of the emitted
energy, with highest amplitude in the center, bandwidth as configured,
the amplitude is dropping continuously towards the ends for about 70 dB
so. Adjusting the channel bandwidth in the sink block has no influence,
maybe the WBX anyway does not support adjustable filtering?!
Even the simplest possible setup, like random source, OFDM modulator and
URSP, shows this behavior.
What am I doing wrong?
Btw., the spectrum analyzer is a professional device and out of any
LTE, DAB and DVB-T is shown as expected.