Roy Lewallen wrote:
"OK, I give up. I`ve got a dipole in free space. I connect one end of
the load resistance to one end of the dipole. What do I connect the
other end of the resistor to?"

Great question. You connect it to the inobtrusive convenient perfect
earth connection immediately present at the end of the terminating
resistor. Since this is likely impossible, you merely define you have
done the deed and calculate the results.

Best regards, Richard Harrison, KB5WZI

On Tue, 20 Nov 2007 21:38:55 -0800, Roy Lewallen
wrote:

If that's too tough, how about just a dipole a quarter wavelength above
ground?

Hi Roy,

Hmmm, too tough.

The math is all pretty ordinary and well within your capacity to
examine in your own copy of the book. So I won't belabor others with
that. However, as others do not have a copy, they might appreciate
some other benchmarks:

End Fed Half-Wave 600 Ohms
which, of course, suffers the same question;

Folded Quarter-Wave Dipole 260 Ohms
there, a resistor might comfortable be applied, but I don't know as I
have not tried it; yet and all, this is drawn from the same ordinary
math;

Folded Half-Wave Dipole 500 Ohms
same observation as with the Quarter-Wave and falling nearly on twice
the rating too - a coincidence of the math no doubt; (But I believe
there is a commercial variant of this that is popular with the MARS
group exactly for the reasons of not presenting SWR.)

Continuous Wire Array 300 Ohms
an oddity in the pantheon of styles, yet it too seems suitable to
resistive termination for testing "Surge Impedance;"

Rhombic Antenna 600 Ohms
here's one that is more familiar to all, and with the added bonus that
it is typically loaded with a resistor to exactly fulfill the
definition of "Surge Impedance" whose ordinary math dovetails with
experience.

But, Roy, I do recognize the terms "Surge Impedance" maybe a language
barrier with you as it certainly qualifies as an archaic term. Reggie
loved to carry this water and in spite of differences, his treatments
quite often got him results that were good first approximations, and
sometimes better.

If you really seek closure, I would suggest you could mine your own
copy of this reference for errors. As for its practical importance -
well, let's just say that this board would support only 2% of the
current traffic if it came to that.

73's
Richard Clark, KB7QHC

On Tue, 20 Nov 2007 23:48:14 -0600, (Richard
Harrison) wrote:

I also doubt the
presence of an interruptor to discharge either the capacitance or
inductance in the resonant antenna.

Hi Richard,

Heinrich Hertz might have something to discuss with you about his
experiments. Having said that (and undoubtedly upsetting an Arthurian
apple cart in the process) you are too kind to wish:

If Art`s antenna is novel, useful, and not completely obvious from prior
knowlege, he may profit from it. I wish him all the best.

I think Sarnoff's QSO with HMS Titanic search ships may have eclipsed
the novel use and fulfilled the prior art part of this. [AKA all
things are known and/or have been done already.]

73's
Richard Clark, KB7QHC

"Cecil Moore" wrote
If there is not a Z0-match to the feedline at the feedpoint, some
of the antenna current reflected from the open end of the antenna
leaks back into the feedline and makes it's way back to the source.
A TDR will register reflections both from the feedpoint and the
open ends of the antenna.
_________________

Not that this changes the essential point Cecil writes about, but...

The waveform transitions of most TDRs have bandwidths far greater than the
matched bandwidths of typical antennas, so the antenna system would produce
a reflection of the TDR pulse even _with_ a Zo match to the feedline at/near
the design frequency of the antenna.

For that reason a TDR is a relatively useless means to measure the
performance of an antenna, unless the bandwidth of the pulse is contained
within the matched bandwidth of the antenna, and that pulse is modulated on
an r-f carrier in the spectrum that the antenna is intended to radiate well.
The link below leads to an accurate measurement of a broadcast TV transmit
antenna system I made some 35 years ago, using this approach. This system
used about 1,550 feet of 6-1/8" OD, 75 ohm coaxial transmission line.

This measurement might also interest those who think that discrete
reflections do not exist inside a transmission line.

http://i62.photobucket.com/albums/h8...easurement.gif

RF

Richard Harrison wrote:
Roy Lewallen wrote:
"OK, I give up. I`ve got a dipole in free space. I connect one end of
the load resistance to one end of the dipole. What do I connect the
other end of the resistor to?"

Great question. You connect it to the inobtrusive convenient perfect
earth connection immediately present at the end of the terminating
resistor. Since this is likely impossible, you merely define you have
done the deed and calculate the results.

Another way to mentally view the surge impedance is with
an infinitely long wire for the dipole. It changes the
dipole from a standing-wave antenna into a traveling-
wave antenna. The ratio of V to I is constant and equal
to the characteristic (surge) impedance of the antenna.

Reg claimed the feedpoint (surge) impedance for an infinite
dipole would be about 1200 ohms, i.e. ~600 ohms in each
direction which roughly agrees with the formula 138*log(4D/d).
--
73, Cecil http://www.w5dxp.com

On 20 Nov, 21:54, (Richard Harrison) wrote:
Art wrote:

"How many pages soes that book of Bailey`s have?"

595 and each one is valuable.

Best regards, Richard Harrison, KB5WZI

Just bought it for $1.99 plus shipping on E Bay
Art

On 20 Nov, 21:48, (Richard Harrison) wrote:
Art wrote:

"Oh Richard, you may deny my antenna but that is what I was alluding to.

Again it is the LC ratio that must be kept for resonance."

I don`t know enough about Art`s antenna to deny it. I do know that
resonance depends on the reciprocal of the sq. rt. of the product of LC,
not its quotient.

Explosive results from an inductor were introduced by Kettering, I
believe, through interruption of battery current through an inductor to
generate a very high voltage spark to ignite the fuel air mixture within
the cylinder of an internal combustion engine for automobiles. Just as I
doubt the inclusion of a pendulum in Art`s antenna, I also doubt the
presence of an interruptor to discharge either the capacitance or
inductance in the resonant antenna.

If Art`s antenna is novel, useful, and not completely obvious from prior
knowlege, he may profit from it. I wish him all the best.

Best regards, Richard Harrison, KB5WZI

Richard,
You just have to familierise yourself with what ia termed a TANK
circuit
When you do this all becomes clear.Since it is used in transmitters
it may well be included in ARRL publications. On the other hand
"Google"
the circuit. My guess is that it in the older books of Terman where if
you
see a chapter on spark transmitters it will appear in there.
Another good place to look would be Bailey's book with
reference to a flyback transformer. This is a very important area
to hone your antenna skills. Side note. I am not interested in profit.
Regards
Art

Art wrote:
"Hust bought it for $1.99 plus shipping!"

Outstanding! I`ll wager you enjoy it as much as I do..

Data sheets for many common antennas are very nice. They all have
dimensions for 200 MHz but scale for any frequency. Gains are versus a
1/2-wave dipole.

Bailey published "TV and Other Receiving Antennas" in 1950 to "to give
usable information which in many cases is based on the author`s
experience and has not been published before." Bailey lists himself
simply as a consulting engineer.

Best regards, Richard Harrison, KB5WZI

Art wrote:
"I am not interested in profit."

Conglomerate I worked for acquired Newport News Shipbuilding and Drydock
Company. They had their mission statement on a sign in front of their
headquarters. It read something like: "Our goal is to build fine ships,
for a profit if possible." That sign had to go immediately. Our company
was in business for profit which we expected as a consequence of
product, price, and service, even when building nuclear submarines for
the U.S. Navy.

Profit is good. Profit makes the world turn sanely.

Best regards, Richard Harrison, KB5WZI

Art wrote:
"How many pages soes that book of Bailey`s have?"

595 and each one is valuable.

If I ever get a gob of spare time, I might run my copy through a
scanner and give it the same conversion I did a couple of years ago
for Laport's "Radio Antenna Engineering". If somebody wants to help
out and do some/all of the scanning of their own copy, and send me the
files for conversion and processing, it'd be much appreciated - drop
me a note.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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