On Thu, 15 Apr 2004 09:20:59 -0700, jopl wrote:

.
A Traveling-wave antenna is used for satellite up-link communication.
The signal is a microwave frequency up into the (multi) GHz region of
radio waves. The transmitting tube is a traveling-wave tube, which is
powered by a special pulsed amplifier.

A familiar use for this set-up is to relay telephone signals (from U S
Sprint, etc.) up to the satellite and then down load to another ground
station where the signal is converted back into a telephone signal and
sent (over land line) to the person you called. This eliminates the
use of land-lines most of the way for your long-distance telephone
calls.

There are also many military uses for this type of technology.

By the way, the signals are fed from the amplifier through Wave-guides
(a hollow rectangular cross-section sections that are held together by
flanges), rather than by wires. It would be similar to a squared-off
hose section, connected to other hose sections, if this makes the
concept easier to understand.

Waveguides have much less loss than wire or cable and because of the
ultra-high frequencies involved, are much more efficient.

Hopes this gives you some idea of this type of communication.

Regards

warren

warren wrote:

On Thu, 15 Apr 2004 09:20:59 -0700, jopl wrote:

.
A Traveling-wave antenna is used for satellite up-link communication.
The signal is a microwave frequency up into the (multi) GHz region of
radio waves. The transmitting tube is a traveling-wave tube, which is
powered by a special pulsed amplifier.

A familiar use for this set-up is to relay telephone signals (from U S
Sprint, etc.) up to the satellite and then down load to another ground
station where the signal is converted back into a telephone signal and
sent (over land line) to the person you called. This eliminates the
use of land-lines most of the way for your long-distance telephone
calls.

There are also many military uses for this type of technology.

By the way, the signals are fed from the amplifier through Wave-guides
(a hollow rectangular cross-section sections that are held together by
flanges), rather than by wires. It would be similar to a squared-off
hose section, connected to other hose sections, if this makes the
concept easier to understand.

Waveguides have much less loss than wire or cable and because of the
ultra-high frequencies involved, are much more efficient.

Hopes this gives you some idea of this type of communication.

Regards

warren

And here's a site that talks about power waves:

http://www.thepowerwave.com/

:-)

ac6xg

I think my beverage, a traveling wave antenna, would be rather poor for
satellite use.

"warren" wrote in message
...
On Thu, 15 Apr 2004 09:20:59 -0700, jopl wrote:

.
A Traveling-wave antenna is used for satellite up-link communication.
The signal is a microwave frequency up into the (multi) GHz region of
radio waves. The transmitting tube is a traveling-wave tube, which is
powered by a special pulsed amplifier.

A familiar use for this set-up is to relay telephone signals (from U S
Sprint, etc.) up to the satellite and then down load to another ground
station where the signal is converted back into a telephone signal and
sent (over land line) to the person you called. This eliminates the
use of land-lines most of the way for your long-distance telephone
calls.

There are also many military uses for this type of technology.

By the way, the signals are fed from the amplifier through Wave-guides
(a hollow rectangular cross-section sections that are held together by
flanges), rather than by wires. It would be similar to a squared-off
hose section, connected to other hose sections, if this makes the
concept easier to understand.

Waveguides have much less loss than wire or cable and because of the
ultra-high frequencies involved, are much more efficient.

Hopes this gives you some idea of this type of communication.

Regards

warren

Warren wrote:
"A traveling-wave antenna is used for satellite up-link communication."

The similarity between the "traveling wave tube" and the "traveling wave
antenna" is that both are wideband devices.

The helical beam antenna is not considered a traveling wave antenna,
though it does enjoy a wideband response. The traveling wave tube also
employs a helix and enjoys a wideband response but is not usually an
antenna.

Many microwave amplifiers are capable of only 1% of the center frequency
bandwidth. The traveling wave tube was developed to give more than 10%
bandwidth. It was invented in England in 1943.

The traveling wave amplifier generates an electron beam similar to that
of a CRT, but the beam is confined within a long helix. The signal input
is to the electron gun end of the helix. The signal output is taken from
the collector end of the helix.

The traveling wave amplifier electrons are modulated by the signal
traveling along the surface of the helix. Interaction between electrons
in the cathode beam and signal on the helix promotes signal growth and
accumulation as the signal travels to the output end of the helix.

John D. Kraus, inventor of the monofilar axial-mode helical antenna
(helical beam antenna) notes that it: "---has inherent broadband
properties, posessing desirable pattern, impedance and polarization
characteristics over a wide frequency range." (page 268, 3rd edition of
"Antennas")

Kraus` 1948 helix had a pitch angle of 14-degrees, 6 turns, 0.31
wavelength diameter, and a center frequency of 400 MHz. Its pattern was
satisfactory over the 300 to 500 MHz range.

Kraus says:
"Although the helical beam antenna consists of a continuous conductor
carrying a traveling wave, it is also a periodic structure with period
equal to the turn spacing as considered in Sect.8-8. (page 271, 3rd
edition of "Antennas)

Best regards, Richard Harrision, KB5WZI