Richard Clark wrote:


Knowing that Arthur only reads his own threads, I won't have to
anticipate his rejection of the following efficiency reports for a
non-gaussian antenna. From NIST (the people who know efficiency)
about their 60KHz antenna system:

"Each antenna is a top loaded monopole consisting of
four 122-m towers arranged in a diamond shape.
A system of cables, often called a capacitance hat or
top hat, is suspended between the four towers.
This top hat is electrically isolated from the towers,
and is electrically connected to a downlead suspended
from the center of the top hat. The downlead serves
as the radiating element.

"Ideally, an efficient antenna system requires a
radiating element that is at least one-quarter wavelength
long. At 60 kHz, this becomes difficult. The wavelength is
5000 m, so a one-quarter wavelength antenna would be
1250 m tall, or about 10 times the height of the WWVB
antenna towers. As a compromise, some of the missing
length was added horizontally to the top hats of this
vertical dipole, and the downlead of each antenna is
terminated at its own helix house under the top hats.
Each helix house contains a large inductor to cancel
the capacitance of the short antenna and a
variometer (variable inductor) to tune the antenna
system.

"Using two transmitters and two antennas allows the
station to be more efficient. As mentioned earlier, the
WWVB antennas are physically much smaller than
one quarter wavelength. As the length of a vertical
radiator becomes shorter compared to wavelength,
the efficiency of the antenna goes down. In other words,
it requires more and more transmitter power to increase
the effective radiated power. The north antenna system
at WWVB has an efficiency of about 50.6%, and the
south antenna has an efficiency of about 57.5%.
However, the combined efficiency of the two antennas
is about 65%. As a result, each transmitter only has to
produce a forward power of about 38 kW for WWVB to
produce its effective radiated power of 50 kW."

73's
Richard Clark, KB7QHC

The NIST folks could probably increase the efficiency to greater than
90% if they dug a large pit to temporarily store the decaying electrons.
All of those dying electrons lying on the ground tend to discourage the
active electrons from working as hard as they could.

The efficiency could be raised to nearly 100% if the two helices were
wound in opposite directions. That would provide the best shot at
equilibrium.

73,
Gene
W4SZ

On Mon, 15 Oct 2007 19:48:48 GMT, Gene Fuller
wrote:

However, the combined efficiency of the two antennas
is about 65%. As a result, each transmitter only has to
produce a forward power of about 38 kW for WWVB to
produce its effective radiated power of 50 kW."

The NIST folks could probably increase the efficiency to greater than
90% if they dug a large pit to temporarily store the decaying electrons.
All of those dying electrons lying on the ground tend to discourage the
active electrons from working as hard as they could.

The efficiency could be raised to nearly 100% if the two helices were
wound in opposite directions. That would provide the best shot at
equilibrium.

Hi Gene,

You shave points too close. They could achieve 130% efficiency if
they simply tapped into the current return on the inside of the wire.

Arthur's 3dB here and 3dB there, if you use enough wire, then you are
beginning to talk about GAIN!

Also, Fort Collins is a higher altitude than Podunk Illinois, so
impedance is less than 377 Ohms too! High gain, maybe 129% efficient.

***** irony mode off ********

Load resistance seen by the transmitters is roughly 0.85 Ohm
transformed to 50 Ohms.

73's
Richard Clark, KB7QHC