[TowerTalk] perspective

George Fremin III - K5TR geoiii@kkn.net
Thu, 20 Jul 2000 06:36:47 -0700

On Thu, Jul 20, 2000 at 08:58:17AM -0400, K3BU@aol.com wrote:
> Isn't gain of antenna tied to pattern? 

Yes it is.

The way I see it is this:

The world is a noisy place at HF frequencies.  This noise comes
from all directions - it can be worse in some directions.
At HF you are limited by the noise seen by the antenna.

If a signal is above the noise you will be able to hear it.

If the signal is below this noise then an increase in gain
in the direction of the signal will increase the noise
by the same amount.

At HF you can do several things to improve your abiltiy to 
hear signals.

Have a VERY quiet location. 
(This worth more than most know.)

Use an antenna with a very good pattern - so that it rejects
the noise from every direction except the one you want to hear.

If you increase the gain in the direction of a signal
you will increase the level of the signal but you will
also increase the level of the noise the same amount - this will
not help you hear this signal any better.

Forward gain is a good thing as it usually means you are 
narrowing the pattern of the antenna down so that it hears
less noise, but it is this increase in patten (rejection of noise)
that is the real improvement. 

When you design an antenna for HF you want to get a good 
pattern - even if it means giving up some forward gain.
You will not hear the 1 or 2 db improvment in forward gain
but you will hear an improvment if you can make the pattern
better thus rejecting unwanted noise.

Now to go back to the quiet location - most of us would 
improve our hearing ability more by spending the time to 
find a quiet location than by debating about minor changes in
the antenna system.  If you can't move - then you need to
be spending your efforts getting rid of ALL of the power
line noise, electric fence noise etc.


George Fremin III                 
Johnson City, Texas             "Experiment trumps theory." 
K5TR (ex.WB5VZL)                            -- Dave Leeson W6NL

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