Since you can log in, all is not lost and you should not have to reimage the pi to get things working. If you type in a program name (like ls) at the prompt and there is no explicitly specified path,

My guess is that your PATH environment variable was removed. If you type echo $PATH (echo is built into the shell), you should get something like /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbi

I don't think a transformer will pass a signal of a few Hz without doing weird things to the signal's waveform. Thank you for including the link. I had not read that before. That was interesting to re

I think I remember reading that 9600 bps requires DC coupling to the modulator. Transformer coupling would be a problem if that is the case. Eric WB6TIX

Excellent. Eric WB6TIX

If what I think is happening..... The file that you get after you "unzip" it is a disk image that needs a special (but free and easy to get) program to copy it to tbe SD card. The disk image includes

Systemd, or not, makes yet another issue that determines the solution that works. Eric

I don't have a pi4, but I do have the image, which I mounted to take a look around. I'm more of a Slackware Linux person, but I think I muddled through the process of getting dns stuff. systemd....hmm

If your pi is automatically getting an ip address from the router, is the router set to provide dns addresses? The dhcp client often overwrites the resolv.conf file to reflect the information coming f

I moved all but the boot off to a USB thumb drive..and now the file accesses seem much slower. Is this expected, or am I imagining things? I'm using a Pi3B+ and a USB 2.0 capable thumb drive. Eric

Deviation METER.... autocorrect got me! :-)

A service monitor with a deviation meyer will also work. Eric