Quote below.

The on-channel TDR pulse performance of a narrowband antenna can be seen by
controlling the RF bandwidth and spectrum span of the test process to fit
the application. The pulse (ping) itself is modulated onto an RF carrier
set at the operating frequency.

Not practical for most hams, but very useful in evaluating and optimising TV
transmit antenna systems.

If anyone is interested in seeing a jpg of such a measurement, pls e-mail me
directly.

- RF

_____________

"Tam/WB2TT" wrote in message
What happens when you ping your antenna? Clearly the spectrum of the pulse
is wider than the bandwidth of a typical antenna, but is there any useful
information?

Mike, KB3EIA wrote:
"But the idea of signals being actually reflected seems hard to
swallow."

It`s true that antennas are measured in degrees. A 1/4-wave antenna is
90-degrees. This is based on how many degrees the signal has changed at
the antenna input by the time the signal reaches the tip end of the
antenna.

When signal reaches the end of a 1/4-wave whip, there is an abrupt
discontinuity. Only displacement current flows without conductors. The
tip of the whip accepts only a small fraction of the current available
in the forward power traveling on the whip. The only path for the
rejected power is back toward the feedpoint. Direction and phase of the
current reverse in the reflected power, but the voltages of the incident
and reflected waves have the same phase (see 1955 Terman, page 89).

Best regards, Richard Harrison, KB5WZI

(see 1955 Terman, page 89).

Best regards, Richard Harrison, KB5WZI

===========================

From where can I obtain a Frederick Emmons Terman prayer mat ?
;o)
----
Reg.

On Mon, 24 May 2004 17:32:48 +0000 (UTC), "Reg Edwards"
wrote:

From where can I obtain a Frederick Emmons Terman prayer mat ?
;o)
Same place that sells the Kelvinator sacred artifacts and lord
plushbottom hymnals.

"*" wrote in message ...
They make an instrument called a Time Domain Reflectometer,
you hook it up to transmission lines and it sends out a pulse
and times how long it takes to get back.
The time it takes, reflected pulse polarity, and height says a lot about
the
line.
Used for finding faults on telco/cable lines.
Does the same thing with RF lines.
Matched well, no pulse, but you can even see connectors on some of these
TDR's
Googleit, too

Sorry, *, won't work. TDR only good on wide band systems. Too messy
for this kind of antennas.
--
Steve N, K,9;d, c. i My email has no u's.

Richard Harrison wrote:

Mike, KB3EIA wrote:
"But the idea of signals being actually reflected seems hard to
swallow."

It`s true that antennas are measured in degrees. A 1/4-wave antenna is
90-degrees. This is based on how many degrees the signal has changed at
the antenna input by the time the signal reaches the tip end of the
antenna.

When signal reaches the end of a 1/4-wave whip, there is an abrupt
discontinuity. Only displacement current flows without conductors. The
tip of the whip accepts only a small fraction of the current available
in the forward power traveling on the whip. The only path for the
rejected power is back toward the feedpoint. Direction and phase of the
current reverse in the reflected power, but the voltages of the incident
and reflected waves have the same phase (see 1955 Terman, page 89).

Thanks Richard. I'm digesting that now. Let's see it any of it sinks in !

- Mike KB3EIA -

"Richard Fry" wrote in message
...
Quote below.

The on-channel TDR pulse performance of a narrowband antenna can be seen
by
controlling the RF bandwidth and spectrum span of the test process to fit
the application. The pulse (ping) itself is modulated onto an RF carrier
set at the operating frequency.
- RF


Duh! I should have known. Pulse it within the BW of the load.
Steve N.