Medstar Montgomery Medical Center Linked to MAIPN Backbone
On Sunday, April 28, a dish was added to the existing MAIPN backbone node in Aston, MD, establishing a link to Medstar Montgomery Medical Center in Olney. Here are a few photos.
We want to express our appreciation to Tony, K3WX, for hosting a MAIPN backbone node on his commercial tower in Ashton.
The diagram below illustrates some of the planning we do prior to installation.
We start with an elevation profile obtained from Google Earth, and sketch in the dish heights above ground level at both ends of the link. The path length in this case is 3.73 miles. We obtain the diameter of the Fresnel zone from this website:
Note that the downtilt is exaggerated in this diagram, because the horizontal and vertical scales are different. (The actual downtilt is a small fraction of a degree.) Nevertheless, we can easily read off the height of the path above ground level at any point along the path.
In this diagram, we have assumed that the height of the dish on the tower was 100′ above ground. This indicates we have a problem, because the center of the path is only 55′ above an intervening ridge, and trees on that ridge are approximately 100′ high. Getting the dish on the tower up to the 160′ level helps, but doesn’t resolve the problem.
The inset (again, from Google Earth) shows what’s on the ground where the path crosses over the problematic ridge. Fortunately, there is a partial clearing surrounding a house, but we have to accept any loss due to the trees until we can find a better path.