I've worked Don, also -- he's pretty local and very strong on 40CW in the late afternoons before the band stretches out. I read his writeup and didn't see anywhere he plotted switching vs. frequency other than to write "HF" and such. The spectrum analyzer captures are cool but I didn't see anywhere he defined the X axis for actual frequency. I don't think his switch using 1N4007s will work at 1.8 MHz. Of course, technically, that's not "HF," it's really "MF" (HF starts at 3 MHz), so this wouldn't be a correction to anything he wrote. But it would be interesting to test it all on 160m. My guess is: It won't work.