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Re: [Discuss-gnuradio] An interesting application for my new USRP... som
From: |
Larry Doolittle |
Subject: |
Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested |
Date: |
Tue, 24 May 2005 14:10:28 -0700 |
User-agent: |
Mutt/1.5.9i |
John -
> [chop], there
> will be three or four signals, on different frequency bands (near 3.58,
> 7.08, 14.08, and 21.08 MHz). The signal will be an unmodulated carrier
> (well, there will be some CW identification) and will be transmitted for
> about 10-15 minutes.
>
> It seems to me that with two of the Basic RX boards, I could monitor all
> four frequencies simultaneously and save the data streams to disk
It sounds like a single acquire channel would be enough, the signals
are low enough to acquire without aliasing at 65 MS/s.
> for
> processing with a deep FFT to extract the average frequency of each
> signal over the run.
FFTs suck for this kind of precision work.
Instead, think of it as a curve-fitting excercise.
Test your process ahead of time with some simulated signals.
> Since I'll know the frequency ahead of time to
> within a few kHz, I won't need to capture a wide swath -- probably 10kHz
> on each RX input will do.
Right, but do the filtering digitally instead of analog.
> Since Matt tells me the USRP can be clocked by an external reference, I
> should be able to extract very accurate frequency information
In principle, you could dedicate a second channel to recording the
GPS band, and extract near perfect frequency calibration from that.
Unfortunately for your time-frame, GPS reception in itself is a
serious project that has not been fully solved by the GNU Radio
community (i.e., Krzysztof).
> 2. If I clock the USRP from a highly stable external reference, is
> there any other source of possible frequency error in the system (since
> we're at HF, I shouldn't need to use a downconverter)? In other words,
> will the measured FFT frequency have any error source other than errors
> in the external reference?
Not in the long term. Any acquisition hardware adds phase noise,
but that mostly averages away for the measurement you want to make.
> This sounds like fun. Any ideas/suggestions would be greatly appreciated.
Keep us posted.
- Larry
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- [Discuss-gnuradio] An interesting application for my new USRP... some input requested, John Ackermann N8UR, 2005/05/24
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested,
Larry Doolittle <=
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, John Ackermann N8UR, 2005/05/24
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, n4hy, 2005/05/26
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, n4hy, 2005/05/26
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, John Ackermann N8UR, 2005/05/26
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, n4hy, 2005/05/26
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, John Ackermann N8UR, 2005/05/26
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, n4hy, 2005/05/26
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, Larry Doolittle, 2005/05/26
- Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested, John Ackermann N8UR, 2005/05/26