I just realized, I have a source with some power on 630 meters. My old Navy URM-25 signal generator, very stable and has an auxiliary input for audio. I'm listening to it now on my Yaesu FTdx3000 and its been on for about 40 minutes and has drifted about 5-10 cycles at the most, maybe less. When I turn the output all the way up, I can peg the "S" meter on the 3000 when I just touch a clip lead to the coax of my 80m dipole. I don't know the power output with this setup but I think it has possibilities Here's the rock solid signal on WSJT-X as received on my 3000 and the frequency counter.