General > General Technical Chat
Elevation plot between two geographic locations
Someone:
--- Quote from: abeyer on September 06, 2023, 12:27:33 am ---https://www.heywhatsthat.com/ has some tools with a slant towards line-of-sight radio propagation.
--- End quote ---
Thanks! I couldn't remember the name of that (and google searches didn't turn it up). Such a great free tool.
floobydust:
What the project taught me about relying heavily on contour maps and the software omitting:
1. Any hills, buildings etc. between nodes (had to add a repeater at a hill top)
2. One node is in a valley (has to clear trees and the valley side) or there is a cliff
3. Tree height is not included
With a high tree line, a taller mast means longer cable, and the coax losses were many dB more. Master site it was better to put the radio near the antenna and use a longer data cable lead-in.
Above certain heights, the mast gets classified for lightning and airplane issues.
The treeline also shades any solar power making the day quite short. We have bears and moose that scratch their backs on the masts and knock them out of alignment. Even a few degrees wobble or rotation in wind (you have to cement in the masts with supports) can scuttle signal strength.
The system was installed in late Fall and worked but failed next Spring. It was the new tree leaves growing out with the short antenna masts that did not look over them. The Boreal forest is easily 30-50 ft. tall trees.
This was 868MHz and 902-928MHz ISM (32cm) where water (in tree leaves, rain etc.) attenuates RF, about 10-20km runs and 1W +30dBm TX power. I can't recall the antenna but guessing 9dB Yagi.
I would ask on RF forums about the range/frequency for your project. 50miles is a long run, I could not see it being done on the cheap.
CatalinaWOW:
Over 50 miles be sure to include earth curvature in your calculations. Topo maps and most related databases give heights relative to a reference spheroid (basically sea level). It takes a good sized tower is needed to see fifty miles even over "flat" terrain.
metrologist:
yeah, never mind the hills. It looks like a spherical cap.
Someone:
--- Quote from: CatalinaWOW on September 07, 2023, 01:47:23 am ---Over 50 miles be sure to include earth curvature in your calculations.
--- End quote ---
Care of https://www.heywhatsthat.com/
a view over Sydney:
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