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Re: [Discuss-gnuradio] Help on GRC to transmit at a specific frequency a

From: Josh Blum
Subject: Re: [Discuss-gnuradio] Help on GRC to transmit at a specific frequency and width
Date: Fri, 28 Aug 2009 09:00:07 -0700
User-agent: Thunderbird (X11/20090817)

The sample rate of the signal source is 1M. The sample rate of the usrp2 is 100M/64. Your rates disagree.


dennis wrote:
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

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