Most wireless weather sensors transmit a half-second burst or so every 40-60 seconds around 433MHz... you can pick up a remote temp/humidity sensor from Radio Shack if you or your neighbors don't have one already. I've also seen wireless thermometer setups in Home Depot, Target, K-mart, and the like.
Or, were you looking for something a little faster? Mike > -----Original Message----- > From: > [EMAIL PROTECTED] > [mailto:discuss-gnuradio-bounces+michael.weber=baesystems.com@ > gnu.org] On Behalf Of James Cooley > Sent: Sunday, July 10, 2005 4:18 PM > To: James Cooley > Cc: Eric Blossom; discuss-gnuradio@gnu.org > Subject: Re: [Discuss-gnuradio] FFT of FFTs > > > Any more suggestions on spotting periodic content? (as below?) > > Chiefly, can anyone think of something that I might be able to > definitely pick out within TVRX range? > > -jamie > > > > James Cooley wrote: > > > OK, I'm just getting around to trying these suggestions... First, re > > Eric's suggestions below. > > > > A few quick questions about this. > > > > I'm interested in tuning to a frequency (with usrp/frontend) then > > examining a single stream for periodic content. I've tried this but > > not exactly sure what I'm seeing. > > > > The questions are, have I set this up properly? I have intended to > > grab whatever signal is at 50kHz (arbitrary) above what > we're tuned to > > and analyze that. > > > > How do I best select the feed forward and feed back filter > > coefficients? (I ended up using the tool as written in the > comments). > > > > Also, any suggestions on things to look at within the TVRX > range that > > should definitely test this out? (I think that GSM (TDMA) > bands are a > > bit out of range... up around 900MHz). I wondered if I > could pick out > > the periodicity of NTSC scans perhaps (maybe I'd need like a test > > pattern, eh? to guarantee that the scan is periodic and non > changing > > long enough for me to try it). > > > > > > # xlating filter > > adnl_decim = 1 > > taps = [1.0] > > shift = -50e3 > > capture_rate = usrp_rate > > channel_coeffs = gr.firdes.low_pass (1.0, > # gain > > capture_rate, # > > sampling rate > > 200e3, > # low > > pass cutoff freq > > 200e3, > # width > > of trans. band > > > gr.firdes.WIN_HAMMING) > > xlate_filt = > > gr.freq_xlating_fir_filter_ccf(adnl_decim, > > > channel_coeffs, > > shift, > > capture_rate) > > > > # complex to magnitude > > cplx_to_mag = gr.complex_to_mag() > > > > # > > # Filter Coeffs correspond to butterworth iir > low pass filter > > # passband 0 - 1000 Hz > > # Order 1 > > # > > # > > http://www.dsptutor.freeuk.com/IIRFilterDesign/IIRFilterDesign.html > > # > > fbtaps = [0.29289326, 0.29289326] > > fftaps = [1.0, -0.41421357] > > > > iir_low_pass = gr.iir_filter_ffd(fftaps, fbtaps) > > # fft > > occ_fft = fftsink.fft_sink_f (self, panel, > title="Occupancy > > FFT", > > fft_size = 512, > > sample_rate=usrp_rate, > > baseband_freq=0) > > > > self.connect (src, cplx_to_mag, iir_low_pass, occ_fft) > > > > > > > > > > > > > > > > > > > > > > > > Eric Blossom wrote: > > > >> On Sat, Jun 18, 2005 at 08:18:38PM -0400, James Cooley wrote: > >> > >> > >>> Hi all, > >>> > >>> I'm trying to take an FFT of an FFT.... Basically, I want > to tune to > >>> a signal, and for a given RF frequency, try to spot > periodic usage > >>> of that frequency. Is this possible? What I have now is > hopelessly > >>> slow, so I'm not really sure if I've got it right. > >>> > >> > >> > >> Hi Jamie, > >> > >> Here are a couple of suggestions. If there are relatively few > >> frequencies that you want to observe for periodic > occupancy, I would > >> suggest extracting the frequency bands of interest using a > >> gr.freq_xlating_fir_filter for each one. If there are > lots of them, > >> and they are evenly spaced, then the dft filterbank is > what you want > >> to split them out (blksimpl/filterbank.py). > >> > >> Once you've got your individual streams of signals, for each one I > >> would compute an estimate of whether it is occupied. You could do > >> this by computing the magnitude of the stream > (gr.complex_to_mag) and > >> then low pass filtering that with a gr.iir_filter, > possibly followed > >> by a limiter (which would need to be written). At this point, for > >> each of your input streams, you have an output stream that is > >> effectively a stream of 1's and 0's, where 1 means "is occupied". > >> Then run each of those streams into it's own FFT. Point > this whole > >> pipeline at some kind of TDMA input (GSM basestation?) and > you ought > >> to see the slots (assuming the basestation isn't driving all the > >> slots all the time). > >> > >> Eric > >> > >> > >> > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
