[Antennas] HOW GAIN WORKS

Fri, 23 Apr 2004 16:25:52 -0700

Well, Merv, your colinear aerial is CERTAINLY directional.... that is how it
gets its gain!   There is NO WAY AN ANTENNA CAN GET SOMETHING FOR NOTHING!
However, unlike the flashlight example, it is more like the ceiling fixture
in your home, with the white shade behind the bare bulb ... the elements of
your vertical antenna creates "gain" by taking away from the upward/downward
components, and "squishing" the signal towards the horizon, if you were
communicating with a station up overhead on a mountain, VS a dipole, it
would (most likely!) suffer a decrease in signal strength received, and ...
conversely, you would not receive that transmitter as well as you would with
a dipole, or 1/4 wave vertical, as examples.  That is the reason why some
ham, and commercial, stations employ "tilt" ... to enhance the signal to the
"down the hill" station(s)....
BTW, "tilt" works for verticals, AND other types.. Yagis, Quads, etc....
AND mobiles ... which is why, if you operate in a mountainous area from your
vehicle, it is sometimes wiser to use a 1/4 wave rather than a 5/8 wave or
moreso gain antenna  --- you go up and down the hills, and the "GAIN"
actually becomes a detriment!
And.. the 7dB gain may .. just may ... be questionable... I have both a
(claimed) 6 dB and a 7 dB gain 2M vertical, darn if I can see a difference!
Seriously enjoy these chats, it is great to share info ... been hammin' for
4� years now, still learning something most every day!
73, y'all, Mark  AA6DX

From: <[email protected]>
To: "AA6DX" <[email protected]>; "Merv Stump" <[email protected]>; "'Demetre
Koumanakos'" <[email protected]>; <[email protected]>
Sent: Thursday, April 22, 2004 5:21 PM
Subject: Re: [Antennas] HOW GAIN WORKS

> Then why does my vertical have a gain of 7 db?  It is not directional!
It's a colinear.  W8OKN
>
>
> >
> > From: "AA6DX" <[email protected]>
> > Date: 2004/04/22 Thu PM 11:01:17 GMT
> > To: "Merv Stump" <[email protected]>,
> >         "'Demetre Koumanakos'" <[email protected]>,
> >         <[email protected]>
> > Subject: [Antennas] HOW GAIN WORKS
> >
> > Hey -- just sharing.....let's look ..  an RF antenna can be seen this
way
> > ... a simple FLASHLIGHT, it's dark out  ..      connect the flashlight
bulb
> > to the voltage source, hold it up, bare ... hmmmm .. a  6V bulb can be
seen
> > about 2-3 blocks, depending on "stuff" ..
> >   OK .. now we put the normal FLASHLIGHT  pointing at the receiving
station
> > ... with the killer-diller chrome reflector in place... VOILA!   We get
1000
> > feet, plus! -- -viewing possibility.
> > The antenna, of which we speak, gets gain from the same situation.
Merv
> > has it right!  AND .  the antenna gets it gain from robbing from another
> > direction ...... just like the example..      A  directional flashlight
can
> > be seen for meters, to the front .. and .. TO THE REAR.. just about NIL.
> > How I taught the main idea of a directional antenna for years .. ..
YAGI,
> > Quad, and all the rest of the gain aerials.  Of course, like usual, Merv
and
> > I will get whuppins .. like .. "Golly, you guys are stupid!'
> > Mark ..     AA6DX
> > ----- Original Message ----- 
> > From: "Merv Stump" <[email protected]>
> > To: "'Demetre Koumanakos'" <[email protected]>;
<[email protected]>
> > Sent: Thursday, April 22, 2004 3:38 PM
> > Subject: RE: [Antennas] WiFi Antenna
> >
> >
> > > Demetre, any antenna which has gain is by definition directional.
There
> > > is no way to get gain except to take from one part of an antenna
pattern
> > > and move it to another.  Think of the basic antenna pattern as a
> > > perfectly round balloon.  If you squeeze the balloon you reduce it's
> > > size at the point you are squeezing and cause it to extend further
than
> > > it was in some other direction.  This extension is gain - there is no
> > > free lunch.  It came from somewhere.
> > >
> > >
> > > Merv, W2OE