In article ,
Martin wrote:

On 25/07/10 10:54, Jeff wrote:

Those ranges quoted are for aircraft thousands of feet above sea
level. The jamming range would be much shorter for boats, probably
10 miles or less.


aSSuming it's a linear relationship, I get 202 mile radius...




Not linear: for a ground level jammer,
The line of sight estimator for distance versus height above sea level
goes something like this:
distance n.m. = 1.2 sqrt (Height ft MSL)

..and of course that assumes that the emitter is at sea level, so if it
is at any appreciable height (or in another aircraft) then you have to
add the result of the same equation again!!

and ignores the surface effect that allows UK TV & VHF signals to be
picked up as far away as in the Netherlands.

Horizontal Bending doesn't work all that well at 1.6 Ghz, and is
negligible, in its effect. Temperature Inversion Refraction is also
negliable at 1.6 Ghz, and even if you could count on any specific
Inversion System to be present at any one time. Both of the above are
present for frequencies below 1 Ghz, and could contribute a small effect
but above 1 Ghz, it just isn't going to happen....

--
Bruce in alaska
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