Hello Adrian,
Welcome to the list.

I am Eric Clegg, KU3I in Sacramento, California.

Fortunately there are a few indoor antennas that can be used by hams in
apartment situations such as myself.

Alex Grimberg in Brazil makes two fine magnetic loop antennas.

One for $129 us dollars that has to be assembled that involves some
soldering and a really unique portable one for $300 us dollars.

There is also one made in the us for about $350.

IN all these cases these are antennas that only accept qrp power.

Wimo Electronics in West Germany sells a very expensive magnetic loop that I
believe will take 100 wats.

There is also a tuning unit with a key pad that will let you input your
operating frequency to the loop.

Unfortunately for me it only runs on 220 volts.

These are the antennas that come to mind at the moment.

I have both Alex magnetic loops and plan to use them with my Kenwood TS590S
running low power.

I believe Martin Lynch and Sons in Britain also sells a few portable
antennas that can be used.

Hope this helps,

73,

Eric
KU3I