Over the last few days I have been receiving quite strong WSPR signals on 472kHz from Richard G4KPX who is in Ely, some 14km north east of me. Looking on the WSPR database I see he has been copied up to 573km on the band using WSPR. Now, in a email from Richard today he revealed his secret: he is using just 1W RF into an indoor 3m x 2m single turn loop made of 10mm pipe leaning against the wall of his spare bedroom! The EIRP is at most 100uW and probably a lot less because of the losses with mounting it where he does and the capacitors used to resonate it. This is a pretty amazing set of results.
Richard has been spotted across the Atlantic on 160m using the same indoor antenna and has similar magnetic loop antennas for all HF bands I believe.
So, if you believe you have no space for an MF band TX antenna, and you don't even have a garden to put a couple of earth-electrodes in the ground, you could always follow Richard's example.
Some months ago I believe one of the German 136kHz stations (DF6NM?) tried something similar using a large coax as a big indoor loop on 136kHz and also got some quite decent results. Never say you cannot erect an antenna! What you need is a bit of ingenuity.