So, the whole "quik n easy" hook a cap between 1pps and RF input is looking less wonderful. I wired 1k and 100pF in series from the 1pps to the 50 ohm input. (when I first tried it, it was just some wire twisted together.. maybe 10 pF). Why those values? I found the 100pF caps first. In any case, when I digitize with the RTL tuned low (5 Mhz)- I get two spikes - one for rising, one for falling. BUT, when I tuned the RTL up band (say, to 15 MHz), I started to get a more "flat topped pulse" in my total power detection (rms over 1 millisecond). How odd? Turns out, when the 1pps is *high*, it's also kind of noisy, and that couples into the RTL through the larger capacitor. See attached "betweenpulse" and "duringpulse" spectra - I happened to run this one at 1.44 MHz sample rate so it's +/- 720 kHz. I have no idea if 14.8 MHz is some sort of significant frequency inside the uBlox, or if it's just grounding the wire which shunts noise that's being picked up. I suppose I could fool around and find a capacitance that couples just the "edge" through, but not the noise during the "on time". or some sort of more complex circuit. Or, I could build some sort of cal burst generator. But I think what I'll do is go back to the original plan of radiating a pilot tone with some modulation to all channels.. (see pulses3.png)