First issue is I didn't have any wires that had the pin connector end. I ended up finding some some header connectors that I could cut some pins off of so that I could have single tall pin I could alligator clip onto.
I put that through a 1nf cap into the LPF I built previously, into my dummy load, and looked at the output on the scope. Didn't like what I saw - definitely some harmonics in there. Was getting about 2.3v p2p
Next I decided to see if my amp would do better. I put the output of the raspi into the Mighty Mike amp, into the LPF, into the dummy load. Much better! The output looks pretty clean. Doing 23.3 Vpp, which is about 1.3w/31dBm.
Ran this command:
sudo wspr --repeat --terminate 7 KC9DLM CM87 31 40m
Waited a few minutes, goofing around and what not.
And then I checked wsprnet.
This is so exciting I can't even explain. Especially given I just threw this together in like an hour.
The IRF510 is probably a bit hotter than it should be (I don't think I even adjusted the bias level since I put that board in a box six months ago).
I hopped over to a SF area web sdr (http://22.214.171.124:8901/) and found my signal :)
The farthest looks to be VE6JY at maybe 1970km away, followed by NO1D at about 1000km. The closest seems to actually be someone in my town :)
So, that looks to maybe be 941 Miles/watt. Not the most impressive, but given my antenna is not that high (nor have I ever verified the SWR on it) and it is is around 1pm on 40m, I'm pretty happy with that.
edit: tried again later (8:45pm) - the 40m band is maybe better at night :)