These were formulas I had written in my notes about 30 years ago, when I
worked in Satcom for the military and NASA.
I think they used an efficiency of 55 percent
another was 20log D(feet) + 20log F(mhz) - 52.4 = dbi
and the main formula of gain in db = k(pi*D/wave)squared ....showing
k=0.55, d is diameter, wave is the operating frequency
On 10/8/2010 9:47 PM, jimlux wrote:
Brian Kirby wrote:
20 log(base10) (diameter in meters) + 20log(frequency in ghz) +17.8 = dbi
That assumes some nominal efficiency?
I'll have to remember that one.. 17.8
It's like the 32.44 dB for free space loss between isotropes 1 km apart
at 1 MHz
(+20log10(dist in km) + 20log10(freq in MHz))
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