[TowerTalk] Rai Beam

[K4SB]

wa4dou@juno.com wrote:
>   I don't believe for a second, that the 2 element Raibeam produces a
> gain of 8
> dbi, which translates into 5.9 dbd., but for the sake of the arguement,

Roy made a very good presentation in his arguments. However,
along with a lot of others, he is mixing apples and oranges with
the dbi and dbd. You simply cannot subtract the 2.15 dbi gain of
a free space dipole, and come up with dbd. A common dipole over
real ground will have a gain of about 6.5 to 8 db. Against a
similar antenna, it gain in DBD is 0. I have 3 wide spaced long
boom yagis for 10, 15, and 20. They generally average out at
about 15.7 dbi gain over real earth but, to get to dbd, you have
to subtract the gain of a dipole at the same height, and at the
same angle of radiation. As Roy noted, that leaves us with about
8 dbd gain.

Again, taking Roys general position, there is no such thing as
something for nothing. I don't care how you phase them, space
them, or what, the simple truth is that every compromise you
make, whether using traps, shortening the boom, or any other will
result in a decrease of gain from a reference standard.

And another factor, reports such as I worked XX1XX with a 20/9
signal mean absolutely nothing, especially as you go higher in
frequency to say 28 Mhz. When propagation is right, 1 watt into a
bedspring will sound like a wrong coast kilowatt.

You can believe these inflated gain figures, and a lot of us
"want" to, but the simple truth is antennas follow the same laws
as anything else.

73
Ed

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