A The Doctor was once faced with a similar problem while living in a condominium. My solution was the old open the window slightly and place a board there scheme.
See Figure 1. Cut a piece of 2 × 4 lumber so that it fits snugly into the lower sash. Drill a hole large enough to pass your coaxial cable. Pass the cable through the board and through the window.
Close the window onto the board and use another length of board between the top of the window and the upper frame to prevent the window from being opened from the outside. Connect the coax to your antenna, but leave enough slack in the cable to form a drip loop just outside the window. Finally, buy some packing foam material and use it to block any drafty gaps created by your new installation. When it’s time to move, the entire assembly can be torn down in minutes without damage to the window.
Figure 1—A narrow 2x4 with a properly drilled hole will pass a coaxial cable through a window without damaging or modifying the window itself.
From QST June 2000
