I was asked if I could write some instructions describing how to get RT-11 to boot in an emulator, so here goes...
To boot a PDP-11 in the SIMH emulator (on Windows), the first thing you need is a copy of the SIMH program. You can get that from here: http://simh.trailing-edge.com/sources/simhv38-1-exe.zip
From that zip file we're interested in the application called "pdp11.exe", you should easily find it inside the root of the zip file. Extract pdp11.exe to a folder on your PC - this is the SIMH emulation of a PDP-11. It won't do anything interesting yet though.
The next thing that you need is some software to run on the emulator, I've been using the RT-11 OS and you can download that here: http://simh.trailing-edge.com/kits/rtv53swre.tar.Z
That is a compressed set of RT-11 files, including a disk image. Inside, there should be a /Disks folder containing the disk image called "rtv53_rl.dsk". Save that dsk file to the same folder where you saved pdp11.exe.
Now we need to tell SIMH to boot, and to do that we create an ini file and save it into the same folder as pdp11.exe. You can do that in notepad. The ini file should have this content:
set rl enable
set cpu 512k
set cpu 11/53
attach rl0 rtv53_rl.dsk
Save that content as "pdp11.ini" in the same folder as everything else. It will tell SIMH to emulate a PDP-11/53 with 512k or RAM, and boot from the disk image.
Now you should be able to run pdp11.exe and it should boot from the disk and start running a brand new copy of RT-11. You're on your way...