I recently got the Sony XDR-F1HD's brother, a Sony XDR-S10HDiP, the one that is a small, plug in boombox. Hence the question here about these radios.
I've found my XDR to be a phenomenal MW/AM band performer, even on a few feet of wire attached to one side of the AM terminal on the back of the radio. Looping it makes it work even better.
With just the 6-8 ft. length of wire it was roughly equal to my PR-D5.
The only 'glitch' is there is something in the RFI environment that must be tripping the HD on some MW frequencies, and I get infrequent one second dropouts, accompanied by the 'HD' icon flashing during the dropout.
It pulls in both local AM HD stations well, and the sound is very good, FM-like. ON DX, so far, it will indicate that it is 'seeing' an HD signal, but still plays those stations in mono analog (KSL, KRKO, etc. -- regional stations with HD AM).
To loop the wire, Mofocat, just get a 6-8 ft. length (or more) of wire and plug each end into the dual AM terminal. I have my loop of wire just looped over a nearby lampstand for the time being. Works great.
The Sony XDR's have an NXP DSP chipset inside, including a chip that tunes to the external antenna (not unlike the SiLabs DSP chips in many modern radios).