October 9, 2020

Calculating the line-of-sight radio path

VHF and UHF radio communication are most commonly based on line-of-sight propagation.  Line-of-sight is the thus the ordinary limiting factor which determines how far your signal will reliably travel.  There is a really great free tool for visualizing the line-of-sight path between two GPS locations.

Recently, I worked a station through the W6CX Mt. Diablo repeater from the summit of Mt. Lassen 292 km (182 miles) away, using my 5W Kenwood TH-F6A HT.  Below is the line-of-sight plot between the two summits using scadacore.com.  I simply entered the GPS decimal coordinates for the two locations and scadacore.com automatically produced the the radio path study and a google map showing the two locations.  This was quick and easy to do.

Radio path study between the summits of Mt. Diablo and Mt. Lassen

You can find GPS decimal coordinates for a location easily using Google Maps.

  1. On your computer, open Google Maps
  2. Right-click the place or area on the map or type in an address in the search
  3. Select, "What's here?"
  4. At the bottom, you’ll see a card with the coordinates
  5. Click on the card to open it
  6. Highlight the GPS decimal coordinates on the card to copy

The scadacore.com google map is interactive which allows you to move the points around and instantly see the plot.  This is a very helpful way to explore possible paths between two locations.

Good DX and 73, NJ2X

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