Here's a limited space stealth antenna that is so easy to make and costs so little you might not even think it will work, but I assure you that it can. It's a Hi Q loop. You can make it mostly with things you have around your house or apartment. You will need:
A hula hoop (you probably can get one at a thrift shop if you have to, but even if you buy one it's a small cost)
Two old pill bottles. One needs to slide into the other. Not the smallest ones, but not too big either
A length of insulated wire, roughly one fifth the length of the hoop
A few pieces of scrap wire and some wide clear tape.
Wrap strips of aluminum foil around all but two inches of the hoop. Try to do two layers of foil. On the side of the hoop opposite the bare two inches attach the insulated wire (only mechanically, not electrically) with a few pieces of tape so it forms a loop as indicated in the picture.
You will attach the coax (center and braid) to the ends of this smaller loop.
Make your tuning capacitor out of the pill bottles. Wrap the smaller one with a few layers of aluminum foil strips, then one layer of clear plastic tape to insulate the foil. This will slide into the other bottle which will be lined on the inside with strips of foil. Attach a wire to the foil on each bottle (tape it, slide it under the foil, etc. whatever works best for you). Attach your wire leads to each "side" of the foil where the bare two inches of hoop show. Try to keep the leads short (maybe shorter than mine!).
This method worked best when I made this homemade variable capacitor. You may try a different design. If you're having trouble getting the antenna to resonate, add a 6-12 inch long piece of coax to the capacitor terminals (braid to one side, center to the other). This will add some capacitance. Then retune the variable capacitor.
Prop the hoop upright (or place it on a chair or on a non-conducting pole) and attach an SWR analyzer, noise bridge, etc. to the opposite end of the coax attached to the smaller loop, and adjust the capacitor (slide the inner bottle in and out) for the best SWR. You will have to experiment with the capacitor, the shape of the smaller loop and the position of the antenna so be ready to do that. It may take some fiddling, but eventually you will find a match and can then attach your rig to the antenna and make some contacts. The RF energy is coupled inductively to the larger loop through the smaller loop. A few things to remember:
DON"T TOUCH THE ANTENNA WHILE TRANSMITTING! You could get a burn.
I'd only put about 5-10 watts into the hoop. It isn't made for high power. And don't sit too close to the loop (to minimize RF exposure). If there is any arcing in the capacitor, stop transmitting.
You may have to adjust the capacitor sometimes, and readjust the capacitor every 20 kc or so if you move frequency.
This antenna is definitely for use under a roof, not out in the elements for an extended time!
Using CW and even some SSB I have used loops like these to talk to stations on four different continents. This particular one worked Europe and North and South America just today. It resonated best on 20 meters and seemed also to work on 17 meters. Those bands are good places to start with your loop. Also it is so low cost and simple it's a great conversation piece. As always, use caution and be careful when building and transmitting. Good luck!