Bill Turner wrote:

On Wed, 07 Apr 2004 17:42:58 GMT, Richard Clark
wrote:


There is no gain in any antenna.


__________________________________________________ _______

Wow! Wait till the engineering world hears about this!

--
Bill, W6WRT
QSLs via LoTW

If it is a passive device, which it is, there is no gain.

There is vector addition and subtraction of EXH fields to form a beam.
That's math!!

However, I don't know of any Yagi, Quad, 4-square, that with 100 watts
into the antenna and 100 watts radiated, assuming 100% efficiency, has
any gain!! It has directivity!!

Now, my Ameritron 80B takes 65 watts in and delivers 900 watts out.
That's gain! It converts 1400 watts plate power to 900 watts rf [key
down conditions].

Dave Shrader wrote:
However, I don't know of any Yagi, Quad, 4-square, that with 100 watts
into the antenna and 100 watts radiated, assuming 100% efficiency, has
any gain!! It has directivity!!

Hey Dave, crack out your trusty IEEE Dictionary and reference their
definition of gain. It's not the same as yours. According to the IEEE
and Balanis, the only difference between directivity and gain is the
antenna efficiency. A 100% efficient antenna would have gain equal to
directivity. Sorry, that's the definition.
--
73, Cecil, W5DXP




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I don't have an IEEE dictionary so I stand corrected. However, 100 watts
into a Yagi, Quad, Log Periodic, or 4-square and 100 watts radiated is
still 0 dB gain.

Gain = 10 * Log[Pout/Pin] = 10 * log [100/100] = 10 * 0 = 0 dB.

It also has 0 dB attenuation!!!

NB: Valid over either 4*Pi or 2*Pi steradians.

Cecil Moore wrote:

Dave Shrader wrote:

However, I don't know of any Yagi, Quad, 4-square, that with 100 watts
into the antenna and 100 watts radiated, assuming 100% efficiency, has
any gain!! It has directivity!!


Hey Dave, crack out your trusty IEEE Dictionary and reference their
definition of gain. It's not the same as yours. According to the IEEE
and Balanis, the only difference between directivity and gain is the
antenna efficiency. A 100% efficient antenna would have gain equal to
directivity. Sorry, that's the definition.
--
73, Cecil, W5DXP




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Bill Turner wrote:

SNIP



Ask any Top of the Honor Roll DXer whether his beam has "gain". Don't
be surprised if his eyes glaze over as he contemplates what must be the
world's rawest newbie.

--
Bill, W6WRT
QSLs via LoTW


With all due respect Bill I am not a newbie! [see below]

His beam, assuming 100% efficiency, is only 0 dB gain.

Gain [dB] = 10 * Log[Pout/Pin] = 0 dB.

The Honor Roll holder, much to his chagrin, still has a 0 dB gain
antenna. He may have an amplifier that puts out 1500 watts, no feedline
loss and a 100% efficient antenna. He is still radiating 1500 watts and
that is by definition 0 dB gain.

The double integral of ExH across theta from 0 to Pi and Phi from 0 to
Pi is constant in both cases. Therefore 0 dB gain!!!

Deacon Dave, W1MCE [for 50 years]
Program Chief Engineer, USAF MX Missile, RS/RV

Let's see... 65 watts + 1400 watts in gives 900 watts RF + 565 watts of
heat out (neglecting filament power.) How much gain is that? :)

73,
Bob AD3K

Dave Shrader wrote:
...Now, my Ameritron 80B takes 65 watts in and delivers 900 watts out.
That's gain! It converts 1400 watts plate power to 900 watts rf [key
down conditions].


--
Robert L. Spooner
Registered Professional Engineer
Associate Research Engineer
Intelligent Control Systems Department

Applied Research Laboratory Phone: (814) 863-4120
The Pennsylvania State University FAX: (814) 863-7841
P. O. Box 30
State College, PA 16804-0030

Dave Shrader wrote:
I don't have an IEEE dictionary so I stand corrected. However, 100 watts
into a Yagi, Quad, Log Periodic, or 4-square and 100 watts radiated is
still 0 dB gain.

Dave, that's true for the entire surface of a sphere at 100% efficiency
but you are still not using the IEEE Dictionary definition of antenna
gain. From Balanis: "... the power *gain* is usually taken in the direction
of maximum radiation." i.e. not over the entire sphere but over a small
area where the radiation intensity is at a maximum. The gain over isotropic
would then be based on the ratio of maximum radiation intensity per unit area
from the beam to the average radiation intensity per the same unit area from
an isotropic antenna. To obtain the (G)ain, one can calculate the (D)irectivity
and multiply by an efficiency term.

G(theta,phi) = e(cd)[D(theta,phi)]

where anything in parentheses is a subscript. e(cd) is an efficiency
term based on conduction and dielectric losses. If efficiency equals
100%, gain equals directivity. (theta,phi) are vertical and horizontal
angles related to a chosen area on the surface of a sphere.
--
73, Cecil, W5DXP



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On Thu, 08 Apr 2004 08:32:58 -0700, Bill Turner
wrote:
Try this:

1. Attend a meeting of your local DX club.

2. Announce in a loud voice that all their fancy beams have exactly
zero dB gain.

3. In addition, announce that when feedline losses are included, their
fancy beams actually have less gain than a dummy load (because of the
shorter feedline).

4. See how long it takes to receive an invitation to join the club.

:-)

All simply an argument for engineering through democratic vote. I
wouldn't cross a bridge designed that way.

I have a 100W transmitter, name me one antenna that will radiate more
than 100W from this source. Then we can put a "gain" figure to it.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
I have a 100W transmitter, name me one antenna that will radiate more
than 100W from this source. Then we can put a "gain" figure to it.

The ONLY difference between antenna directivity and antenna gain, by
definition, is efficiency. Therefore, it logically follows that you
are asserting that no antenna possesses directivity. Care to prove
that outrageous assertion? Maybe you better stick to optics?
--
73, Cecil, W5DXP

Dave Shrader wrote:
I don't have an IEEE dictionary so I stand corrected. However, 100 watts
into a Yagi, Quad, Log Periodic, or 4-square and 100 watts radiated is
still 0 dB gain.

Gain = 10 * Log[Pout/Pin] = 10 * log [100/100] = 10 * 0 = 0 dB.

It also has 0 dB attenuation!!!

NB: Valid over either 4*Pi or 2*Pi steradians.

What you've calculated here is efficiency, not gain. It's important to
understand the difference between the two if you want to communicate
with others about antennas.

Roy Lewallen, W7EL

Richard Clark,

I fully support your "All antennas have zero gain" campaign.

Why not join the "There's no such thing as an SWR meter" campaign?
----
Reg, G4FGQ