Thanks everyone for the responses. Enough for now. Time to make anything happen. Will let you know and perhaps start a new thread around this. Regards Paul WB8TSL
On Sat, Oct 24, 2020 at 10:17 PM Graham / KE9H <[email protected]> wrote: > Paul: > > The easiest way to convert a single sample into an I-Q representation is to > have a two phase local oscillator. > You multiply the incoming signal against the primary phase output of the > oscillator for the I channel, > and multiply the same sample against the 90 degree offset output for the Q > channel. > > The quadrature oscillator can be as simple as two sine look-up tables, > whose entries are shifted by 90 degrees. > The only math is in the sample multiply, and creating the look up tables to > start with. > > If there is a ratio of integers relationship between the sampling rate and > the desired local oscillator frequency, then you can get a real clean > implementation with reasonably small look-up tables. When running there is > no transcendental math involved, just a simple multiply. > > --- Graham > > == > > On Sat, Oct 24, 2020 at 7:37 PM paul swed <[email protected]> wrote: > > > Antenna and filtering are not a problem for me. I use the 10' X 10' > square > > loop and about 800' of wire with a cap to resonate at 60 KHz and then a > > preamp really to drive 140' of coax. Currently using a modified KD2BD > > receiver frontend but using a 350 Hz xtal filter. Yes indeed that hamfest > > find was amazing. > > > > Looks like you have to build a costa loop SDR. Looked at lots of > documents. > > My first question to the group. > > Can a single incoming sample be converted to I & Q through math. I sort > of > > think so. The original sample might be I and then use math to make Q. > That > > would save an entire analog chain. The teensy has a single chain for mic > > level input. Though it does feed left and right channels. Granted there > are > > two audio chains at line level. > > > > The teensy has a NCO that can create a quadrature output. The alternate > > would be to use that to drive analog switches as a multiplier to form I > & Q > > samples. > > Regards > > Paul > > WB8TSL > > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
