Thanks Tom and Marcus for taking time out and explaining things on the list.
-- Bob > > > How do you determine the size of taps? How much of a difference does > > setting the transition width from 1MHz to 10MHz make? > > > Generally, the wider the transition width, the fewer taps. > > You can use the "firdes" functions, which is what the low-pass filter > blocks call in gnuradio, then take their output into a variable and > have another variable be len(filter). > > > > > > On Tue, Nov 19, 2013 at 6:40 PM, Marcus D. Leech <mle...@ripnet.com > > <mailto:mle...@ripnet.com>> wrote: > > > > I really appreciate the detailed explanation. I tried running > > gr_filter_design last night and it asked me to install SciPy, > > which I did not feel like doing at that time. I will try using > > 1MHz for my band, which may help get rid of the real-time > > running issue. > > > > Again, I appreciate your help with this matter. > > > > Let's say you get a filter that's, oh, I dunno, 100 taps long. > > That filter has to process every sample, so, that's 5e7 X 100 taps, > or > > roughly 5e9 FLOP/second. Just for that one filter. And your > > flow-graph is likely doing other things *and* it's having to get > > samples > > all the way through your network or USB stacks into the > > application layer as well, call that 100 instructions/sample. So, > > that's > > 5e7 x 100 = 5e9 OPS/second just to get your samples into the > > application. You're going to burn-up the cycles on your CPU pretty > > quickly at 50Msps, even for doing "trivial" things. > > > > > > > > > > > > -- > > Marcus Leech > > Principal Investigator > > Shirleys Bay Radio Astronomy Consortium > > http://www.sbrac.org >
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