"John S" wrote in message
...
:

0 deg 1.09 dBi @ 12.5 deg
30 deg 1.37 dBi @ 12.5 deg
45 deg 1.66 dBi @ 12.5 deg


I would appreciate a definition of gain as used in this thread. I have a
hard time understanding how a passive device can supply gain.

Thanks,
John

If you look above you will see dBi. That is dB over an isotropic antenna.
That type of antenna is not possiable to make, but a math modle. It is
single point where the power is radiated from equally in all directions.

To get "gain" you take some of the power in some directions and put in
another direction. For sake of discussion, look at a simple dipole. There
will not be much radiation off the ends of the antenna so there will be more
at right angles to the wire. The differance is the 'gain'. As I mentioned,
gain by its self does not help and can actually hirt the signal if it is not
in the right direction.

The gain of the verticals , unless designed for a certain distance, does not
mean much unless you can tilt it so the maximum gain lobe is heading in the
direction you want.

At field day one fellow was always wanting to put up an extended double Zep
for the low bands. He talked about the gain. While it has gain in some
directioins, it has 'loss' or 'negative gain' in others, but he was not
thinking about that, just raw gain numbers.


I have up a 3 element beam for 20, 15,10 meters and also an off center fed
antenna that is about 125 feet long near the same height. On 20 meters in
some directions the OCF and beam are at almost the same strength. At
others, there is around 20 dB of differance.. It is just not practical to
rotate that OCF. If it was, I would just use it.




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