You're probably remembering correctly, and that likely included some consideration for other factors (other than pure line-of-sight) as well. I don't know offhand, but you're probably both right!I will have to revisit some old notes on this. Back when we were designing some 5 mile long microwave paths I remember having to add around 50 feet to the path calculations to accomodate earth curvature, but I'm going on memory here and it's certainly not perfect!
Thanks for the sanity check, Poppy. This number seems more reasonable. The number I was origiinally thinking of included a fresnel zone clearance figure so that threw me off at first.
That of course is if my source is correct. Afterall, I did get it from the internet, so it must be right, right?Thanks for the sanity check, Poppy. This number seems more reasonable. The number I was origiinally thinking of included a fresnel zone clearance figure so that threw me off at first.
A six foot man can see about 3.1 miles to the horizon.
Therefore 21 miles divided by 3 is 7 (six feet tall) for a total of 42 feet height
Eh, in the case of the former and you wish to avoid the attention of ne'er-do-wells sure. In the latter you may well wish to summon attention.For me this just points out the need for light management in a SHTF or weather emergency.
In an actual emergency situation (be it a power outage, forced movement in darkness, major disaster) they generally represent excess - more power consumption, light output, and mass - that costs you in terms of runtime, dark adaptation, and carrying other stuff.Big lumen lights are not your friend