Dale, Thanks for the reply. Yes, that occured to me and I actually set up a tone and tuned across it and did that. I thought Bob was describing a way in which one could actually see the filter shape by using noise, much like you could view a filter by exciting it with a noise source and looking at the output with a spectrum analyser.
Tom Dale Boresz wrote: > Tom, > > You could set up an XG1 or XG2 outside the passband of the filter, > then tune the radio so that the signal from the XG1 sweeps into the > passband and out the other side, while you write down relevant > frequencies (from the VFO display) and dBm amplitudes (from the > s-meter). Then do your calculations. It's a bit time-intensive, but I > believe it will produce accurate results. > > Dale > WA8SRA > > > Tom Thompson wrote: > >> Tom Thompson wrote: >> >> >> >>> Bob, >>> >>> In April you wrote the following: >>> >>> We use Blackman-Harris windows for all the right reasons as the >>> window in the filter design. We care about the ultimate out of band >>> rejection, and this can only be accomplished by a (VERY SMALL) >>> sacrifice in shape factor. These filters in their worst case, >>> 192000 samples per second and DSP set to 512 sample buffers, BETTER >>> than can be had with any traditional analog filtering system. >>> >>> >>> This is easy for you to do yourself. >>> >>> Set display to spectrum. Set filter size. Go to Setup panel and >>> test tab and turn on the noise generator and select input. This will >>> run white noise into the receiver and you can measure the filter >>> shape DIRECTLY and capture screen shots to demonstrate the filter >>> shape. >>> >>> Frankly, we are just too covered up with other work to do this now. >>> But it is easy to do. >>> >>> Bob >>> >>> I understand the directions, but I expected to see the noise >>> spectrum follow the filter skirts instead of being flat across the >>> panadapter. What am I missing here? >>> >>> Thanks & 73, >>> >>> Tom W0IVJ >>> >>> >>> >> >> >> Bob, >> >> In thinking about this a bit more after my post, I understand why the >> noise would appear flat across the panadapter. I guess my question >> is: How do you get the shape factor of the filter? >> >> Tom W0IVJ >> >> >> >>> _______________________________________________ >>> FlexRadio mailing list >>> FlexRadio@flex-radio.biz >>> http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz >>> Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ >>> FlexRadio Knowledge Base: http://kb.flex-radio.com/ >>> FlexRadio Homepage: http://www.flex-radio.com/ >>> >>> >>> >>> >>> >>> >>> >> >> >> >> >> _______________________________________________ >> FlexRadio mailing list >> FlexRadio@flex-radio.biz >> http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz >> Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ >> FlexRadio Knowledge Base: http://kb.flex-radio.com/ >> FlexRadio Homepage: http://www.flex-radio.com/ >> >> >> >> > > > > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
