[Discuss-gnuradio] Help on GRC to transmit at a specific frequency and width

[dennis]

Hi @ all

Sorry, this stuff is new for me and therfore sorry for a possible stupid 
question ;-) . I play a little with GRC and want to transmit e.g. a 
cosine-wave at a specific frequency e.g. at 900MHz and width, say 2MHz. 
But my problem are as following:

If i add only 2 blocks, i got nice constant transmission  but the width 
are too large, say more than +- 30 Mhz
 __________             ______________
|   signal   |           |                      |           source: 
sample_rate: 1M, waveform:cosine, Frequency: 1k, Amplitude: 100
|  source   |--------->|  usrp2 sink   |          usrp2 sink: 
interpolation: 64, Frequency: 900 MHz, Gain: 0
|__________|           |______________|

Is it possible to add a filter between the singal source and the usrp2 
sink, maybe the band pass filter? Or is ist only possible with a 
hardware filter behind the ursp2?
In case of the band pass filter: which values are right? I tried: 
decimation=1, gain=1, samplerate=200k, lowcut=200k, highcut=200k, 
transition width=200k. Or shoud the low- und highcut equals to the 
frequency at 900 MHz and therfore a samplerate of 1.8 GHz?
I played a while with various values but without success.

thanks in advance
Dennis