It's important to remember how the A40C works on shortwave, seeing some of the puzzled responses on here.
When the set is switched to short-wave, a broadband converter is brought into operation. The centre frequency is set by the subsidiary dial to the right of the main scale and has a bandwidth of about 1MHz.
Now, the output of this converter is fed into the set at the AC/TP as though it was switched to medium wave and you can then tune across this broad spectrum of signals provided by heterodyning a chunk of the SW bands. So it's a sort of, but quite, a dual-conversion set. The aerial is disconnected from the MW/LW front end and connected to the converter's input, whilst the converter output is now connected as above. See the attached.
Of course, if you go dangling a wire on or near the AC/TP you will get MW breakthrough even though it's set to SW.