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[email protected] · April 4th 14, 06:45 PM posted to rec.radio.amateur.antenna

John S wrote:
On 4/3/2014 7:37 PM, wrote:
Ralph Mowery wrote:

wrote in message
...

Note than because we are now over real ground vertical lobes are formed.

Again I will leave it as an exercise for the reader to get the demo EZNEC
and view the graphs.

droop impedance max gain length SWR

0 deg 22.6 Ohms 2.48 dBi @ 35 deg .245373 lambda 2.12
30 deg 43.4 Ohms 2.24 dBi @ 40 deg .236269 lambda 1.15
45 deg 51.1 Ohms 1.94 dBi @ 45 deg .231667 lambda 1.022

It should be noted that there is a large second lobe:

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

So which antenna is "best" in the real world?

I would go for 5% longer radials drooping at 45 degress.

Now we are getting somewhere in the discussion. For simple antennas that
can not be rotated unless one wants to talk to a certain distance, the
antenna does not make much if any differance. You get 'gain' in one
direction and 'loss' in another. Just match it to the coax and take what
you get.

There is no real gain in an antenna, just redirecting the power that is
supplied to it.

And there is no such thing as cold, just the absense of heat...

Hi, Jim -

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

By definition.

Antenna gain is defined as the ratio of the maximum field strength in the far
field compared to the field strength of an isotropic radiator expressed in
decibels.

That is dBi.

Some times the comparison is to a dipole, in which case it is dBd.

FYI the gain of a lossless dipole is 2.15 dBi.

An isotropic radiator is a theoretical antenna that produces a perfectly
spherical pattern.

--
Jim Pennino