HI
> On Oct 9, 2017, at 8:49 PM, jimlux <jim...@earthlink.net> wrote: > > On 10/9/17 8:02 AM, Bob kb8tq wrote: >> Hi >> Pick a couple of local broadcast stations and record them. That will give >> you a baseline >> for each of the parameters you are after in real time. They *will* drift. >> Past that, I’d go with a sweep of each node before installation. That will >> give you the >> frequency response and (to some degree) a guess for noise and spurs. > > The RTL-SDR has only about 2 MHz BW, so you'd have to be lucky to have a > broadcast station in the band (and if I'm looking at trying to image Jupiter > with an interferometer, at 20.1 MHz, I'm not sure that the SW broadcast bands > cover within 2MHz - and you'd be subject to the vagaries of propagation.. low > sunspots = low critical frequency = not much skywave propagation for WWV). > > So a local reference would be nice. Originally, I thought about just > radiating a CW tone (perhaps modulated with timecode), but then, I realized > I'd also like to calibrate the RF chain in the receiver, so feeding a > calibrated pulse that has spurs (hey, a "marker beacon" in old school radios > with a analog dial) Monitor for 55 minutes and calibrate for 5 minutes. Do the calibration in maybe 10 second segments spread out over the hour. The gotcha with any “radiated” signal is finding a band you can legally transmit it in ….. For an array a few feet on a side, not a big deal. For something a mile or two across, it begins to be an issue. Bob > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
