If you are reading this, you might be like I was, obsessed with getting free HD OTA but (a) concerned that an indoor antenna might not work well enough or at all, (b) already spent the money on an indoor antenna and was disappointed by the results and/or (c) didn't know how to put up an outdoor antenna. Been there, done that
From here onward, proceed at your own risk
This explains how I did it and what was required.
So you have an HD tuner, a view from your balcony in the general direction of the signal sources, are not on very low floor (the lower you are, the more the antenna's visibility to others may be a problem) and have determined other people in your general location are getting HD. Living in a high rise adds complications such as; can't attach anything to the balcony, and (sometimes) can't put anything on your balcony which detracts from the appearance of the building. The following assumes the latter IS a problem.
I used a Channel Master 4221 which is 3 feet high and 1 foot wide, and has a 1 1/4" pole in the middle to slide into a like sized hole in something. As a second mounting option, it has two brackets top and bottom for U-bolt attachment to another vertical pole.
You want to get it high enough for line of sight above the balcony railing. I got 3 small concrete blocks from Home Depot and bolted them together at their long sides. It isn't going to move in any weather, isn't attached to your balcony, and you just shift the position of the concrete blocks to aim the antenna. Buy a 1 1/4" square wood pole (make sure its straight!), treated wood preferred (very cheap at Home Depot). Now you need to attach it to something which in turn attaches to the concrete block. One idea is to bolt several angle brackets to the bottom of the wood pole, then bolt the brackets to the top concrete block, taking care with the bolt positions that the pole is vertical. Use a level. Now attach the 4221 to the pole using the square u-bolts provided with the antenna through the two gold coloured brackets and around the wood pole. Tighten the brackets snug and then use a level to check vertical positioning again.
Next, you might need to make it unobtrusive. Move it as far back on the balcony as possible. I used a small can of Armor Coat "Court Grey" rust paint from CTC, and brush painted the centre pole of the 4221 and its two gold coloured brackets. With that its hardly noticeable from the ground. And you are in business!