If your townhouse deck is not at ground level I suggest that you try using a magnetic loop antenna. I built one from plans at:
http://www.standpipe.com/w2bri/index.htm ...
It worked, much to my amazement. It tunes 20M, 17M, and 15M. I have the parts to next make a 40 meter loop.
Those parts are, 1/2" copper water pipe, high voltage air variable cap (Ocean States Electronics), and a 12V motor to run it (All Electronics).
The 1 meter per side square loop is hanging from the railing of the deck. The weathered copper blends well with the wooden railing. The capacitor and motor set inside a cheap plastic "sweater storage box" from the Dollar Store ($2) on the floor of the 12ft x 12ft deck. Coax (RG-8x) and 2 conductor wire run up to a second floor shack through the window.
Now how well does it work. I have to confess that I also have a GAP Challenger (31ft) vertical tied to one corner of the deck (loop in opposite corner). I told the Committee For Good Taste that the FCC allowed such antennas and that they superceded local laws. 6 years later still there!
The loop has a dipole like pattern off of the "ends". Mine points NE & SW. Stations broadside to the loop are 1-2 S-units better on the GAP. However, stations off of the ends are equal or better than the GAP. You must understand that the dipole pattern provides a nice advantage over a vertical in the favored directions. When they are open the performance on 15 and 17 meters exceeds that of 20 meters. Look at the software on the web site above and note the efficiency of the 1 meter loop on various bands. Mine ranges from 60% to 90%.
Another plus for the loop is its very narrow bandwidth (a drawback to some) It acts as another bandpass filter ahead of the mixer. The narrow bandwidth thus serves to reduce IMD (noise) from out of IF bandpass signals. Thus for some the loop appears to have less noise.
In summary, a magnetic loop does work very well if at least 1-2 diameters of the loop from the ground Mine is 10 ft above ground on the elevated deck. It does favor, as does a dipole, two directions, It does have performance close to a dipole at a "reasonable" height. The capacitor is not expensive ($15). The motor is $12. The pipe is $5/10ft. I suggest small DC motor control kit or a DPDT center off switch and some resistors for motor control. I have cable TV and NO TVI complaints from anyone. At 100 watts on SSB I have turned on one of those cheap touch lamps. There is no RF in the shack. A note - be very careful with feedline beads since if they do not have sufficient impeadance, and are place at a common-mode (shield) current peak, they get hot and waste power. So far I have seen no need for such things with the loop.
Go to the recommended site and give it a try.
Dick N3HKN