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every expression in decibels (voltage) directly correlates to a unique power multiplier ratio.

dB. gain = 10 log (power out / power in)
dB. loss = 10 log (power in / power out)

unfortunately, gain cannot even be calculated until the radiation efficiency of the antenna has been determined. until then, directivity is all that can be discussed. the same could be said in regard to system losses.

gain = radiation efficiency X directivity.

gain and directivity are differentiated. you can have an antenna with 3 dB. of "directivity" (at some angle) but if the radiation efficiency of that antenna is only 50% then "gain" is only 1.5 dB.. directivity does not automatically equal "gain" unless all antennas are assumed to be 100% efficient. i promise you that is not even the case, particularly where commercially manufactured antennas are involved.

you're right about the terrain but the gm 3/4 wl has maximum directivity at 45 degrees above the ground and the -3dB. beamwidth is over 40 degrees wide. comes in handy for working dx in and out of valleys if there is any distance between the antenna location and the surrounding hillside/s.

they perform extremely well (at lower angles) at a mile above sea level over flat desert plain composed of "poor soil."

<blockquote data-quote="freecell" data-source="post: 764104" data-attributes="member: 30">every expression in decibels (voltage) directly correlates to a unique power multiplier ratio.dB. gain = 10 log (power out / power in)dB. loss = 10 log (power in / power out)unfortunately, gain cannot even be calculated until the radiation efficiency of the antenna has been determined. until then, directivity is all that can be discussed. the same could be said in regard to system losses.gain = radiation efficiency X directivity.gain and directivity are differentiated. you can have an antenna with 3 dB. of &quot;directivity&quot; (at some angle) but if the radiation efficiency of that antenna is only 50% then &quot;gain&quot; is only 1.5 dB.. directivity does not automatically equal &quot;gain&quot; unless all antennas are assumed to be 100% efficient. i promise you that is not even the case, particularly where commercially manufactured antennas are involved.you&#039;re right about the terrain but the gm 3/4 wl has maximum directivity at 45 degrees above the ground and the -3dB. beamwidth is over 40 degrees wide. comes in handy for working dx in and out of valleys if there is any distance between the antenna location and the surrounding hillside/s.they perform extremely well (at lower angles) at a mile above sea level over flat desert plain composed of &quot;poor soil.&quot;</blockquote>

[QUOTE="freecell, post: 764104, member: 30"] every expression in decibels (voltage) directly correlates to a unique power multiplier ratio. dB. gain = 10 log (power out / power in) dB. loss = 10 log (power in / power out) unfortunately, gain cannot even be calculated until the radiation efficiency of the antenna has been determined. until then, directivity is all that can be discussed. the same could be said in regard to system losses. gain = radiation efficiency X directivity. gain and directivity are differentiated. you can have an antenna with 3 dB. of "directivity" (at some angle) but if the radiation efficiency of that antenna is only 50% then "gain" is only 1.5 dB.. directivity does not automatically equal "gain" unless all antennas are assumed to be 100% efficient. i promise you that is not even the case, particularly where commercially manufactured antennas are involved. you're right about the terrain but the gm 3/4 wl has maximum directivity at 45 degrees above the ground and the -3dB. beamwidth is over 40 degrees wide. comes in handy for working dx in and out of valleys if there is any distance between the antenna location and the surrounding hillside/s. they perform extremely well (at lower angles) at a mile above sea level over flat desert plain composed of "poor soil." [/QUOTE]

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