Try starting here:
http://www.tvfool.com/?option=com_wrapper&Itemid=90
Enter you ZIP code, then click on the Hybrid or Satellite view button in the upper right corner of the map. Use you mouse to move the pointer to the location of your tower. You can zoom in or out to help locate yourself on the map. At the bottom center of the map, set the antenna height to 40' or what ever actual height you anticipate.
Once the pointer is located on the position of your tower, click the Make Radar Plot button at the top right corner of the map.
The resulting plot will have a new unique URL 'link' ID that you can post.