The above antenna does not have a ground plain such that it is
unbalanced.
If the feed line was buried underground for a distance at least a half
wave long
would the external current on the feed braid leak to earth/ground
where the transmitter
itself would see no interference from the imbalance? A test for this
I suppose is
rubbing your hand over the coax at the transmitter site to see if any
swr variation occur
Art

"art" wrote
The above antenna does not have a ground plain
such that it is unbalanced.
_______________

The DLM antenna is a monopole (DLM stands for distributed loaded monopole).
All practical vertical monopoles require an r-f ground or counterpoise of
some kind.

You might want to contact Robert Vincent to confirm for yourself that this
true for the DLM.

And If it didn't, why would he bother to test it at a site with a
near-perfect, salt water ground system?

RF

On 26 Nov, 07:32, "Richard Fry" wrote:
"art" wrote The above antenna does not have a ground plain
such that it is unbalanced.

_______________

The DLM antenna is a monopole (DLM stands for distributed loaded monopole).
All practical vertical monopoles require an r-f ground or counterpoise of
some kind.

You might want to contact Robert Vincent to confirm for yourself that this
true for the DLM.

And If it didn't, why would he bother to test it at a site with a
near-perfect, salt water ground system?

RF

That's what I said

Richard Fry wrote:

...
And If it didn't, why would he bother to test it at a site with a
near-perfect, salt water ground system?

RF

Because most antennas are measured against a chosen "standard" antenna
which was/is tested over a perfect/near-perfect ground--I'd imagine ...
(today, the "test standard" is likely to be an antenna modeled by
computer software--however, usually it is modeled over a virtual perfect
ground ...)

But then, your standard may be/have-been some bent coat-hanger
established over the poorest ground you could find in the world?

However, you already knew this ... well, most did.

Regards,
JS

John Smith wrote:
But then, your standard may be/have-been some bent coat-hanger

Hey, a new reference standard, dBch
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
John Smith wrote:
But then, your standard may be/have-been some bent coat-hanger

Hey, a new reference standard, dBch

Cecil:

I woke up with a bit of back pain--didn't help the mood here ... that's
changing. chuckle

Regards,
JS

"John Smith" wrote
Because most antennas are measured against a chosen "standard"
antenna which was/is tested over a perfect/near-perfect ground.

And you're thinking that the Vincent DLM was not using the same
r-f ground used by the "standard" antenna?

But then, your standard may be/have-been some bent coat-hanger established
over the poorest ground you could find in the world?

That would benefit Mr. Vincent, not me.

I have used NEC to model a conventional monopole of the same height as the
standard 3.5 MHz DLM in the URI test report. Using an extremely good r-f
ground (0.5 ohms) and 1.5 ohms of matching loss to the monopole produced a
groundwave field of about 238 mV/m for 1 kW at 1 km. A perfect reference
monopole over a perfect ground plane would produce about 313 mV/m for 1 kW
at 1 km.

This field ratio is about the same as given in the URI report for the
standard 3.5 MHz DLM versus the Navy's standard (1/4-wave) monopole, and
relates to an antenna system radiation efficiency for that DLM of about 59%.

Note that this does not come especially close to the claim made for the DLM
as being the near-equivalent of a good 1/4-wave monopole.

RF

Richard Fry wrote:

...
Note that this does not come especially close to the claim made for the
DLM as being the near-equivalent of a good 1/4-wave monopole.

RF

The original question centered around why Mr. Vincent would test a 1/2
DLM over perfect/near-perfect ground when a 1/2 wave monopole only
requires a very minimal ground (indeed, I have seen 1/2 ants. on boats
with NO counterpoise--well, the outer braid of the coax choked off a 1/4
wave down.)

He chose perfect ground because the standard is, at least, usually
tested over perfect/near-perfect ... I'd imagine.

Regards,
JS

"John Smith" wrote
The original question centered around why Mr. Vincent would test a 1/2 DLM
...

What is a 1/2 DLM?

Half-wave dipoles don't require good r-f grounds to radiate well. They are
balanced radiators. All monopoles (including the DLM) do, however.

RF

Richard Fry wrote:
"John Smith" wrote
The original question centered around why Mr. Vincent would test a 1/2
DLM ...

What is a 1/2 DLM?

Half-wave dipoles don't require good r-f grounds to radiate well. They
are
balanced radiators. All monopoles (including the DLM) do, however.

RF

A half wave DLM is one which consists of a 1/2 wavelength radiator ...
google it; or, Vincents patent contains VERY complete data on the
construction of one--he tested it, also, at the Navy complex.

I thought this was the one Arts' original post addressed ...

Regards,
JS